ECU Tendon Injuries in Tennis

What forced Rafael Nadal to retire from the French Open and Wimbledon in 2016?

Warning: This is a comprehensive post

Short on time?

For ‘Quick Tips for Players/Coaches and Physios”, scroll all the way down to the bottom of this post.

 

Rafael Nadal was on the comeback, 2016 was meant to be his year. His knees (chronic patella tendinopathy(s)) were finally holding up well and in the lead up to the 2016 French Open he was performing superbly on Clay; it was the Rafa of old!

Everyone was predicting (or hoping for) a Nadal/Djokovic final at Roland Garros in 2016. Even Rafa was very optimistic in his post-match conferences, confident that he could go all the way this year.

But then, in Round 3 of the French Open, he pulled out of the tournament due to injury and eventually announced that he wouldn’t be at Wimbledon as well. When he walked out to the press, everyone once again looked down to his knees……. but then realised he had a brace on his wrist.

 

Rafa succumbed to an ECU (extensor carpi ulnaris) tendon injury in his left hand (dominant hand). A very common injury in professional tennis players, and probably the recent ‘number 1 enemy’ of tennis injuries leading to loss of match time at elite levels. Wrist injuries are on the rise in elite tennis (http://espn.go.com/tennis/story/_/id/10975718/players-novak-djokovic-experiencing-more-wrist-injuries-espn-magazine), this is due to a generational change in how balls are hit. Long-swings with a long follow-through have been replaced with ‘whip from the hip’ forehands with violently large amounts of topspin. You wouldn’t get away with it with the heavy wooden racquets of old, but the new lighter and comfortable racquets allow it.

This post will summarise the ECU anatomy, tennis-specific biomechanics, pathophysiology, diagnosis and treatment, with some quick tips at the end for players/coaches and physiotherapists dealing with wrist pain.


 
ECU Functional Anatomy — Where is it?

 

The ECU muscle originates at lateral epicondyle of the humerus as part of the common extensor tendon complex. The muscle travels down the forearm with the wrist extensors and enters a 15–25mm fibro-osseous tunnel as a tendon in the 6th extensor compartment. This tunnel sits the ulnar groove on the dorsal aspect of the distal ulna. The tendon is held in its normal position in the ulnar groove by the fibro-osseus ECU subsheath, with the extensor retinaculum superficially arcing over the ulnar to attach to the pisiform and the triquetrum . The ECU tendon then exits the subsheath and runs adjacent to the triangular fibrocartilage complex (TFCC), kisses the triquetrum and attaches to the anteromedial aspect of the 5th metacarpal base.

 

In forearm supination, the ECU tendon exits the ulnar groove at a 30deg angle in the direction of the 5th metacarpal base. With ulnar deviation this angle becomes even more acute, which leads to pathology if an external load is placed on it. In normal wrists, the tendon natural displaces however it is much more pronounced in supination (1–6).

A study on normal displacement of the ECU tendon with the ulnar groove using ultrasound found that the ECU tendon displaced the most during supination (see graph) and the least during pronation.

 

From the 4 wrist positions, ulnar deviation and flexion presented the greatest ECU tendon displacement. In this study, the ECU remained in the ulnar groove with pronation with all four wrist positions, therefore pronation is the most stable forearm position for the ECY tendon (7). Of interest, there was 0.55mm greater displacement in the dominant hand of the 20–25 year old participants of this study, one can only predict that this would increase with age therefore suggesting that with age there is greater displacement potential of the ECU tendon from the ulnar groove.

ECU function — What does it do?

A Distal Radioulnar Joint Stabiliser

Although an ‘extensor’ of the ‘carpus’ or wrist, the ECU tendon provides extrinsic stability to the distal radioulnar joint (DRUJ) (1, 8), whereas the TFCC is the primary intrinsic DRUJ stabiliser. This highlights the role of wrist stability proprioceptive exercises with TFCC injuries to improve DRUJ stability. In supination, the ECU tendon braces the ulnar dorsally to improve DRUJ stability (3). Salva-Coll et al. (2012) summarise that the ECU tendon and its sheath, through their actions on the distal carpal rows, are important to dynamic stability of the wrist. Furthermore, the DRUJ also has a capsule which is made up of the radioulnar ligaments of the TFCC and the floor of the ECU tendon sheet (1), when pronator quadratus and the ECU are tensioned they increase DRUJ stability.

A Lunotriquetral Joint Stabiliser

 

A recent study (9) suggests ECU muscle proprioception training may assist with lunotriquetral (LTq) joint stability because when the LTq joint ligaments have been torn, patients will get pain when making a closed fist as the triquetrum excessively rotates into flexion and supination. The ECU muscle can counteract this rotation which helps reduce friction between the lunate and the triquetrum, thereby helping reduce LTq joint arthritis and/or synovitis (see pic). Contraction of the ECU muscle in isolation also pronates the distal carpal row as well as the scaphoid and the triquetrum (3).

 
ECU Proximity to LTq joint

A Wrist Mover

You’d think Latin would help us out here, Extensor (to extend) Carpi (the wrist) Ulnaris (ulnar side) should tell us that the ECU extends the wrist, but it’s not a prime mover of the wrist as explained above.

In supination, the ECU contributes to wrist extension however in pronation its role as a wrist extensor is limited (10).

Pathophysiology — What goes wrong?

ECU Tendon Instability/ECU Subsheath Rupture

In supination the ECU tendon exits the ulnar groove at an acute angle, this angle is increased with wrist ulnar deviation and flexion, when there is an active contraction of the ECU muscle at the same time (eg: forehand/double-hadned backhand ball impact, see below) it places great stress onto the ECU subsheath trying to hold the tendon in the groove.

 

Repetitive actions with high load (see below tennis and golf examples) will eventually result in ECU subsheath failure and eventually ECU tendon instability, also if there is an high-force impact injury (see below rugby example) (6). Congenital anatomical variation where there is a flattening of the distal ulnar groove has also been proposed to exist and therefore be a risk factor for ECU tendon instability (11).

You can see the ECU tendon subluxing in the following video:

https://youtu.be/re5m__tmPh0

Inoue and Tamra (2001) describe 3 types of ECU subsheath injury:
  1. Ulnar sided ECU subsheath tear: The tendon will sublux but return to the ulnar groove without resting on top of the sheath. Won’t impact on subsheath healing. healing and conservative management.
 
Type 1 — Ulnar sided ECU subsheath tear

2. Radial sided ECU subsheath tear: If the tear is on the radial wall, the tendon will return to the ulnar groove but rest on top of the sheath, this will prevent any chance of healing and is unlikely to respond to conservative treatment.

 
Type 2 — Radial sided ECU subsheath tear

3. ECU subsheath ulnar periosteum stripping: The ECU subsheath tractions the periosteum off the ulna on the ulnar side, this forms a false pouch that the tendon dislocates into, it still reduces back onto the ulnar groove. Can respond well to conservative management. (6, 12)

 
Type 3 — Ulnar periosteum stripping by ECU subsheath

ECU Tenosynovitis

ECU tenosynovitis can occur when there is an extensor retinaculum tear, it can result in mechanical friction between the ECU tendon and the ulnar groove (13).

Tendon instability may also be a risk factor for tenosynovitis where the ECU sheath can be irritated by repetitive flexion/extension, especially when in supination (4). However, it is uncommon in young elite tennis players as the development of tenosynovitis of the ECU tendon is usually associated with arthritis, therefore often presents in much older populations (13).

ECU Tendinopathy

The ECU tendon can develop a tendinopathy if overloaded over time. Tendons are adaptive. When loaded over time they become bigger stronger, when unloaded over time they become smaller and weaker, but when placed under excessive loads for prolonged periods of time they can develop a pathological adaptive response called a tendinopathy.

As part of the ‘biopsychosocial’ model of treatment, with both tenosynovitis and inflammatory tendinopathies, keep in mind the psychological stress status of the player, as it may also delay healing and prolong inflammatory conditions.

Quick and Dirty Summary of the Cook/Purdam Tendon Pathology Model

A continuum model of tendinopathy has been proposed by Jill Cook and Craig Purdam (2009). In early stages of overload, the tendon attracts proteoglycans which bring water in to the tendon resulting in tendon swelling and stiffness, this is the ‘reactive’ tendinopathy stage and usually presents with an acutely sore tendon with activity.

 

With continued excessive loading, tendon matrix begins to breakdown due to an increase in the number of chondrocytic cells, and the body reroutes plumbing into the tendon (blood vessels and nerves), the tendon is now in the ‘disrepair’ stage. The tendon is stiff and sore when playing sports and in the morning when getting out of bed (especially noticeable if it’s the Achilles tendon) but it warms up and becomes less sore.

If ignored and the excessive load continues, the tendon will then enter the ‘degenerative’ stage. Tendon collagen is normally wavy and is linear to the line of pull of the tendon for strength, however in this stage it goes haywire and is progressive disorganised. This causes significant weakness of the tendons structure, increasing the risk of complete tendon rupture (14).

 

ECU Tendon Rupture

The ECU tendon can overtime breakdown to a point where it will rupture completely. Although it has been reported to coincide with a series of corticosteroid injections (6), it is more likely that the player has kept playing through pain and dysfunction for long enough for the tendon to structurally fail. Forehands aren’t usually affected in tennis players, it’s the double handed backhand that will lack power that will finally stop the player from competing. 

Sport-Specific ECU Injuries

ECU injuries frequently occur in Tennis and Golf however ECU injuries are also common in the rugby codes.

ECU injuries in Tennis

Tennis — Grips

The specific grip employed by the player may increase their risk of wrist injury. Before we analyse how wrist injuries occur with forehands and backhands, let’s have a refresher in what the different grips are:

 
https://youtu.be/eRCWkQfPGvg

In a survey of elite tennis players (13) no players utilise the continental grip for forehands. 75% use a semi or full western grip, and 23% (male)/25%(female) use an Eastern grip.

Ulnar side wrist injuries (eg: ECU tendon, TFCC etc.) occurred more often with Western grips (semi and full) whereas radial side wrist injuries occurred more often with Eastern grips (Eg: DQT, intersection syndrome etc.).

We should also try to understand why players would choose topspin (hitting up through the ball) over power (hitting through the ball). A ball with topspin may have the same velocity but it will have a slower speed from A>B. This not only gives the player a defensive advantage, creating time to return to the centre of the court, but it also will provide less room for error as it will clear the net further and drop shorter. Whereas a ball with power with the same ball velocity will have a faster speed from A>B, this will take time away from the opponent and create space. The ball will be closer to the net and will land further towards the baseline.

 

 

Tennis Strokes — Forehands

With forehand strokes a ‘semi-western’ grip increases the risk of ECU injury due to the need to ‘brush up’ through the ball in order to impart spin on the ball. At impact (see picture on right) the forearm is supinated, the wrist would also try to ‘hinge’ into radial deviation and the ECU muscle would isometrically contact to stabilise the wrist.

 
The higher the ball, the more supination required, the more supination, the more the wrist will require a forceful ECU isometric contraction.

The higher the ball is truck in with this grip, the more supination is required in order to flatten the racquet head to hit through the ball (see Djokovic on the left in the above picture, higher ball = increased supination). Nadal utilises a full western grip with his forehands, therefore he is at increased risk of ulnar-sided wrist injuries.

Also, repetitive supination-pronation actions can lead to stripping of the extensor retinaculum. The players do this when ‘rolling the racquet head over the ball’ which increases ball contact-time with strings increasing friction transfer and therefore topspin.

Watch Nadal in the below video at the following times:
00:29–0:33, 1:10–1:13, 2:05–2:08, 2:28–2:31. 

https://youtu.be/B2IduNtpE5I

At these times, you can see that during terminal cocking phase the forearm quickly rotates into supination, the supinated wrist is then forced into end-of-range wrist extension due to the lag of the racquet.

Tennis Strokes — Double Handed Backhand

In tennis, double-handed backhand strokes require the dominant hand to move from pronation to supination forcefully in order to impart topspin on the ball (4). However, it’s the non-dominant hand closest to the racquet head that will be supinated at impact (6). Coaches will often say that the double-handed backhand for a right hander is just a left handed forehand (and vice-versa), therefore the grip on the non-dominant hand will similar to the dominant hand in a forehand.

Biomechanical studies have shown that the non-dominant wrist is in extensive ulnar deviation during the double handed backhand (see Li Na and Maria Sharapova above) (13). Moreover, the higher the ball (see Sharapova on the left) the more supination required in order to flatten the racquet head to hit through the ball (as with a forehand).

As a side note, let us take a moment to feel sorry for tennis coaches, as they are much more prone to developing De Quervains tenosynovitis and intersection syndrome on the radial side of the wrist form high wrist flexion/extension repetition during training (13).
 

Coaches are susecptable to radial (thumb) side wrist injuries due to repetitive ball feeding

Tennis — Court Surface

Of course, players at the elite level have such high training loads that it is unsustainable to continue hitting in an aggravating fashion, fortunately it is probably the seasonal court surface changes that saves them. Different court surfaces results in different ball bounce height. As discussed above, the higher the ball at contact the higher the workload for the ECU.

 

For example, clay Court = high ball = higher incidence of ECU tendon aggravation (eg: French Open and lead up Clay Court tournaments leading to Nadal’s injury) vs Grass Court = lower bounce.

Tennis — Racquet Strings & Weight

Interestingly, in the Tagliafico et al. (2009) survey-study, all the injured players surveyed use synthetic gut over natural gut. Synthetic strings have higher durability whereas natural gut have fantastic elasticity and maintain their pre-set tension longer. Let’s face it, if you go through as many racquets in 1min as Baghdatis does (), who needs durability? Just get the natural gut! :)

https://www.youtube.com/watch?v=g7kS68T6ptA

Players who have increased string tension also have to impart more topspin on the ball and are therefore would also be more at risk of developing wrist injuries. Less string tension results in more contact time with the ball which provides more friction when generative topspin on the ball.

 
 

If a player changes too quickly to a heavier racquet this may also overload the upper limbs, it is common (especially with recreational players) to get shoulder impingement, tennis elbow and wrist stability issues with a sudden change to a heavier racquet. Wean the player onto the new racquet weight slowly over weeks, using the old racquet less and less.

 

Tennis — The Kinetic Chain

50% of the energy needed to hit a forehand is generated from the legs and trunk. As with all sports, an issue in the kinetic chain can have effects downstream. We know that ankle injuries are likely to lead to anterior knee pain. Thoracic issues reducing thoracic mobility often overload upper limbs and lead to one pathology after the other from shoulder impingement, to tennis elbow, to wrist injuries. For example, if knee flexion whilst serving is less than 10 degrees in the cocking phase it places 23% greater load on the shoulder and 27% greater load on the elbow to maintain racquet head velocity. In order to maintain a set racquet head velocity, less power from the kinetic chain pre-shoulder requires a development of power from the upper limbs. The shoulder, elbow and wrist are in the energy-transfer business, not the energy-development business. They participate in the kinetic chain by transfering energy through isometric strength and dynamic stability with a healthy dose of timing. Once they become generators of power for prolonged periods, along come the overuse injuries.

In Nadal’s case, years of bilateral knee patella tendinopathy have probably lead him to this point. Knee flexion is vital in order to generate ground reaction force. Of course, it’s not just that, but as mentioned above, his calendar since the Australian open in January 2016 would have had him on clay courts with higher balls and increased amounts of topspin required.

For a great bedtime read on tennis technique and injury prevention, check out:

USTA’s sports science committee white paper on Tennis Technique and Injury Prevention, http://assets.usta.com/assets/1/USTA_Import/USTA/dps/doc_437_550.pdf

ECU injuries in Golf

In professional golf, wrist injury incidence has been reported to be up to 54% (4). Traumatic ECU subluxation can occur in the ‘leading’ wrist at impact with the ball (or with the ground, if you’re a rookie like me). The club momentum attempts to force the ‘leading’ wrist into ulnar deviation and in order to stabilise the ulnar wrist the ECU tendon contracts isometrically. However, as the trunk and upper limbs above the wrist continue into the follow-through the wrist and the club have a sudden ‘hinge’ into radial deviation in the ‘leading’ wrist. This forceful ‘hinge’ effect combined with the forceful ECU isometric contraction can result in ECU subsheath failure followed by ECU tendon subluxation (4).

 

ECU injuries in Rugby

“Two hands on the ball!!” yells the coach from the sideline. As it turns out, not only is this solid advice as it keeps your opponent guessing whether you will offload the ball, but it will protect your ECU tendon and subsheath as well. Running with the ball cradled against your chest places your wrist in the ECU danger position, and add in the forceful isometric ECU contraction at contact in a tackle and you are at high risk of ECU injury.

 

 
 
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ECU Tendon Injuries in Tennis

What forced Rafael Nadal to retire from the French Open and Wimbledon in 2016?

Warning: This is a comprehensive post.
Short on time?
For ‘Quick Tips for Players/Coaches and Physios”, scroll all the way down to the bottom of this post.
 

Rafael Nadal was on the comeback, 2016 was meant to be his year. His knees (chronic patella tendinopathy(s)) were finally holding up well and in the lead up to the 2016 French Open he was performing superbly on Clay; it was the Rafa of old!

Everyone was predicting (or hoping for) a Nadal/Djokovic final at Roland Garros in 2016. Even Rafa was very optimistic in his post-match conferences, confident that he could go all the way this year.

But then, in Round 3 of the French Open, he pulled out of the tournament due to injury and eventually announced that he wouldn’t be at Wimbledon as well. When he walked out to the press, everyone once again looked down to his knees……. but then realised he had a brace on his wrist.

 

Rafa succumbed to an ECU (extensor carpi ulnaris) tendon injury in his left hand (dominant hand). A very common injury in professional tennis players, and probably the recent ‘number 1 enemy’ of tennis injuries leading to loss of match time at elite levels. Wrist injuries are on the rise in elite tennis (http://espn.go.com/tennis/story/_/id/10975718/players-novak-djokovic-experiencing-more-wrist-injuries-espn-magazine), this is due to a generational change in how balls are hit. Long-swings with a long follow-through have been replaced with ‘whip from the hip’ forehands with violently large amounts of topspin. You wouldn’t get away with it with the heavy wooden racquets of old, but the new lighter and comfortable racquets allow it.

This post will summarise the ECU anatomy, tennis-specific biomechanics, pathophysiology, diagnosis and treatment, with some quick tips at the end for players/coaches and physiotherapists dealing with wrist pain.


 

ECU Functional Anatomy — Where is it?


 

The ECU muscle originates at lateral epicondyle of the humerus as part of the common extensor tendon complex. The muscle travels down the forearm with the wrist extensors and enters a 15–25mm fibro-osseous tunnel as a tendon in the 6th extensor compartment. This tunnel sits the ulnar groove on the dorsal aspect of the distal ulna. The tendon is held in its normal position in the ulnar groove by the fibro-osseus ECU subsheath, with the extensor retinaculum superficially arcing over the ulnar to attach to the pisiform and the triquetrum . The ECU tendon then exits the subsheath and runs adjacent to the triangular fibrocartilage complex (TFCC), kisses the triquetrum and attaches to the anteromedial aspect of the 5th metacarpal base.

 

In forearm supination, the ECU tendon exits the ulnar groove at a 30deg angle in the direction of the 5th metacarpal base. With ulnar deviation this angle becomes even more acute, which leads to pathology if an external load is placed on it. In normal wrists, the tendon natural displaces however it is much more pronounced in supination (1–6).

A study on normal displacement of the ECU tendon with the ulnar groove using ultrasound found that the ECU tendon displaced the most during supination (see graph) and the least during pronation.

 

From the 4 wrist positions, ulnar deviation and flexion presented the greatest ECU tendon displacement. In this study, the ECU remained in the ulnar groove with pronation with all four wrist positions, therefore pronation is the most stable forearm position for the ECY tendon (7). Of interest, there was 0.55mm greater displacement in the dominant hand of the 20–25 year old participants of this study, one can only predict that this would increase with age therefore suggesting that with age there is greater displacement potential of the ECU tendon from the ulnar groove.

 

ECU function — What does it do?

A Distal Radioulnar Joint Stabiliser

Although an ‘extensor’ of the ‘carpus’ or wrist, the ECU tendon provides extrinsic stability to the distal radioulnar joint (DRUJ) (1, 8), whereas the TFCC is the primary intrinsic DRUJ stabiliser. This highlights the role of wrist stability proprioceptive exercises with TFCC injuries to improve DRUJ stability. In supination, the ECU tendon braces the ulnar dorsally to improve DRUJ stability (3). Salva-Coll et al. (2012) summarise that the ECU tendon and its sheath, through their actions on the distal carpal rows, are important to dynamic stability of the wrist. Furthermore, the DRUJ also has a capsule which is made up of the radioulnar ligaments of the TFCC and the floor of the ECU tendon sheet (1), when pronator quadratus and the ECU are tensioned they increase DRUJ stability.

A Lunotriquetral Joint Stabiliser

 

A recent study (9) suggests ECU muscle proprioception training may assist with lunotriquetral (LTq) joint stability because when the LTq joint ligaments have been torn, patients will get pain when making a closed fist as the triquetrum excessively rotates into flexion and supination. The ECU muscle can counteract this rotation which helps reduce friction between the lunate and the triquetrum, thereby helping reduce LTq joint arthritis and/or synovitis (see pic). Contraction of the ECU muscle in isolation also pronates the distal carpal row as well as the scaphoid and the triquetrum (3).

 
ECU Proximity to LTq joint

A Wrist Mover

You’d think Latin would help us out here, Extensor (to extend) Carpi (the wrist) Ulnaris (ulnar side) should tell us that the ECU extends the wrist, but it’s not a prime mover of the wrist as explained above.

In supination, the ECU contributes to wrist extension however in pronation its role as a wrist extensor is limited (10).

 

Pathophysiology — What goes wrong?

ECU Tendon Instability/ECU Subsheath Rupture

In supination the ECU tendon exits the ulnar groove at an acute angle, this angle is increased with wrist ulnar deviation and flexion, when there is an active contraction of the ECU muscle at the same time (eg: forehand/double-hadned backhand ball impact, see below) it places great stress onto the ECU subsheath trying to hold the tendon in the groove.

 

Repetitive actions with high load (see below tennis and golf examples) will eventually result in ECU subsheath failure and eventually ECU tendon instability, also if there is an high-force impact injury (see below rugby example) (6). Congenital anatomical variation where there is a flattening of the distal ulnar groove has also been proposed to exist and therefore be a risk factor for ECU tendon instability (11).

You can see the ECU tendon subluxing in the following video:

 

Inoue and Tamra (2001) describe 3 types of ECU subsheath injury:

  1. Ulnar sided ECU subsheath tear: The tendon will sublux but return to the ulnar groove without resting on top of the sheath. Won’t impact on subsheath healing. healing and conservative management.
 
Type 1 — Ulnar sided ECU subsheath tear

2. Radial sided ECU subsheath tear: If the tear is on the radial wall, the tendon will return to the ulnar groove but rest on top of the sheath, this will prevent any chance of healing and is unlikely to respond to conservative treatment.

 
Type 2 — Radial sided ECU subsheath tear

3. ECU subsheath ulnar periosteum stripping: The ECU subsheath tractions the periosteum off the ulna on the ulnar side, this forms a false pouch that the tendon dislocates into, it still reduces back onto the ulnar groove. Can respond well to conservative management. (6, 12)

 
Type 3 — Ulnar periosteum stripping by ECU subsheath

ECU Tenosynovitis

ECU tenosynovitis can occur when there is an extensor retinaculum tear, it can result in mechanical friction between the ECU tendon and the ulnar groove (13).

Tendon instability may also be a risk factor for tenosynovitis where the ECU sheath can be irritated by repetitive flexion/extension, especially when in supination (4). However, it is uncommon in young elite tennis players as the development of tenosynovitis of the ECU tendon is usually associated with arthritis, therefore often presents in much older populations (13).

ECU Tendinopathy

The ECU tendon can develop a tendinopathy if overloaded over time. Tendons are adaptive. When loaded over time they become bigger stronger, when unloaded over time they become smaller and weaker, but when placed under excessive loads for prolonged periods of time they can develop a pathological adaptive response called a tendinopathy.

As part of the ‘biopsychosocial’ model of treatment, with both tenosynovitis and inflammatory tendinopathies, keep in mind the psychological stress status of the player, as it may also delay healing and prolong inflammatory conditions.

Quick and Dirty Summary of the Cook/Purdam Tendon Pathology Model

A continuum model of tendinopathy has been proposed by Jill Cook and Craig Purdam (2009). In early stages of overload, the tendon attracts proteoglycans which bring water in to the tendon resulting in tendon swelling and stiffness, this is the ‘reactive’ tendinopathy stage and usually presents with an acutely sore tendon with activity.

 

With continued excessive loading, tendon matrix begins to breakdown due to an increase in the number of chondrocytic cells, and the body reroutes plumbing into the tendon (blood vessels and nerves), the tendon is now in the ‘disrepair’ stage. The tendon is stiff and sore when playing sports and in the morning when getting out of bed (especially noticeable if it’s the Achilles tendon) but it warms up and becomes less sore.

If ignored and the excessive load continues, the tendon will then enter the ‘degenerative’ stage. Tendon collagen is normally wavy and is linear to the line of pull of the tendon for strength, however in this stage it goes haywire and is progressive disorganised. This causes significant weakness of the tendons structure, increasing the risk of complete tendon rupture (14).

 

ECU Tendon Rupture

The ECU tendon can overtime breakdown to a point where it will rupture completely. Although it has been reported to coincide with a series of corticosteroid injections (6), it is more likely that the player has kept playing through pain and dysfunction for long enough for the tendon to structurally fail. Forehands aren’t usually affected in tennis players, it’s the double handed backhand that will lack power that will finally stop the player from competing.

 

Sport-Specific ECU Injuries

ECU injuries frequently occur in Tennis and Golf however ECU injuries are also common in the rugby codes.

ECU injuries in Tennis

Tennis — Grips

The specific grip employed by the player may increase their risk of wrist injury. Before we analyse how wrist injuries occur with forehands and backhands, let’s have a refresher in what the different grips are:

 

In a survey of elite tennis players (13) no players utilise the continental grip for forehands. 75% use a semi or full western grip, and 23% (male)/25%(female) use an Eastern grip.

Ulnar side wrist injuries (eg: ECU tendon, TFCC etc.) occurred more often with Western grips (semi and full) whereas radial side wrist injuries occurred more often with Eastern grips (Eg: DQT, intersection syndrome etc.).

We should also try to understand why players would choose topspin (hitting up through the ball) over power (hitting through the ball). A ball with topspin may have the same velocity but it will have a slower speed from A>B. This not only gives the player a defensive advantage, creating time to return to the centre of the court, but it also will provide less room for error as it will clear the net further and drop shorter. Whereas a ball with power with the same ball velocity will have a faster speed from A>B, this will take time away from the opponent and create space. The ball will be closer to the net and will land further towards the baseline.

 

Tennis Strokes — Forehands

With forehand strokes a ‘semi-western’ grip increases the risk of ECU injury due to the need to ‘brush up’ through the ball in order to impart spin on the ball. At impact (see picture on right) the forearm is supinated, the wrist would also try to ‘hinge’ into radial deviation and the ECU muscle would isometrically contact to stabilise the wrist.

 
The higher the ball, the more supination required, the more supination, the more the wrist will require a forceful ECU isometric contraction.

The higher the ball is truck in with this grip, the more supination is required in order to flatten the racquet head to hit through the ball (see Djokovic on the left in the above picture, higher ball = increased supination). Nadal utilises a full western grip with his forehands, therefore he is at increased risk of ulnar-sided wrist injuries.

Also, repetitive supination-pronation actions can lead to stripping of the extensor retinaculum. The players do this when ‘rolling the racquet head over the ball’ which increases ball contact-time with strings increasing friction transfer and therefore topspin.

Watch Nadal in the below video at the following times:
00:29–0:33, 1:10–1:13, 2:05–2:08, 2:28–2:31.

 

At these times, you can see that during terminal cocking phase the forearm quickly rotates into supination, the supinated wrist is then forced into end-of-range wrist extension due to the lag of the racquet.

Tennis Strokes — Double Handed Backhand

In tennis, double-handed backhand strokes require the dominant hand to move from pronation to supination forcefully in order to impart topspin on the ball (4). However, it’s the non-dominant hand closest to the racquet head that will be supinated at impact (6). Coaches will often say that the double-handed backhand for a right hander is just a left handed forehand (and vice-versa), therefore the grip on the non-dominant hand will similar to the dominant hand in a forehand.

 

Biomechanical studies have shown that the non-dominant wrist is in extensive ulnar deviation during the double handed backhand (see Li Na and Maria Sharapova above) (13). Moreover, the higher the ball (see Sharapova on the left) the more supination required in order to flatten the racquet head to hit through the ball (as with a forehand).

As a side note, let us take a moment to feel sorry for tennis coaches, as they are much more prone to developing De Quervains tenosynovitis and intersection syndrome on the radial side of the wrist form high wrist flexion/extension repetition during training (13).
 
Coaches are susecptable to radial (thumb) side wrist injuries due to repetitive ball feeding

Tennis — Court Surface

Of course, players at the elite level have such high training loads that it is unsustainable to continue hitting in an aggravating fashion, fortunately it is probably the seasonal court surface changes that saves them. Different court surfaces results in different ball bounce height. As discussed above, the higher the ball at contact the higher the workload for the ECU.

 

For example, clay Court = high ball = higher incidence of ECU tendon aggravation (eg: French Open and lead up Clay Court tournaments leading to Nadal’s injury) vs Grass Court = lower bounce.

Tennis — Racquet Strings & Weight

Interestingly, in the Tagliafico et al. (2009) survey-study, all the injured players surveyed use synthetic gut over natural gut. Synthetic strings have higher durability whereas natural gut have fantastic elasticity and maintain their pre-set tension longer. Let’s face it, if you go through as many racquets in 1min as Baghdatis does (), who needs durability? Just get the natural gut! :)

https://www.youtube.com/watch?v=g7kS68T6ptA

 

Players who have increased string tension also have to impart more topspin on the ball and are therefore would also be more at risk of developing wrist injuries. Less string tension results in more contact time with the ball which provides more friction when generative topspin on the ball.

 
 

If a player changes too quickly to a heavier racquet this may also overload the upper limbs, it is common (especially with recreational players) to get shoulder impingement, tennis elbow and wrist stability issues with a sudden change to a heavier racquet. Wean the player onto the new racquet weight slowly over weeks, using the old racquet less and less.

 

Tennis — The Kinetic Chain

50% of the energy needed to hit a forehand is generated from the legs and trunk. As with all sports, an issue in the kinetic chain can have effects downstream. We know that ankle injuries are likely to lead to anterior knee pain. Thoracic issues reducing thoracic mobility often overload upper limbs and lead to one pathology after the other from shoulder impingement, to tennis elbow, to wrist injuries. For example, if knee flexion whilst serving is less than 10 degrees in the cocking phase it places 23% greater load on the shoulder and 27% greater load on the elbow to maintain racquet head velocity. In order to maintain a set racquet head velocity, less power from the kinetic chain pre-shoulder requires a development of power from the upper limbs. The shoulder, elbow and wrist are in the energy-transfer business, not the energy-development business. They participate in the kinetic chain by transfering energy through isometric strength and dynamic stability with a healthy dose of timing. Once they become generators of power for prolonged periods, along come the overuse injuries.

 

In Nadal’s case, years of bilateral knee patella tendinopathy have probably lead him to this point. Knee flexion is vital in order to generate ground reaction force. Of course, it’s not just that, but as mentioned above, his calendar since the Australian open in January 2016 would have had him on clay courts with higher balls and increased amounts of topspin required.

For a great bedtime read on tennis technique and injury prevention, check out:

USTA’s sports science committee white paper on Tennis Technique and Injury Prevention, http://assets.usta.com/assets/1/USTA_Import/USTA/dps/doc_437_550.pdf

ECU injuries in Golf

In professional golf, wrist injury incidence has been reported to be up to 54% (4). Traumatic ECU subluxation can occur in the ‘leading’ wrist at impact with the ball (or with the ground, if you’re a rookie like me). The club momentum attempts to force the ‘leading’ wrist into ulnar deviation and in order to stabilise the ulnar wrist the ECU tendon contracts isometrically. However, as the trunk and upper limbs above the wrist continue into the follow-through the wrist and the club have a sudden ‘hinge’ into radial deviation in the ‘leading’ wrist. This forceful ‘hinge’ effect combined with the forceful ECU isometric contraction can result in ECU subsheath failure followed by ECU tendon subluxation (4).

 

ECU injuries in Rugby

“Two hands on the ball!!” yells the coach from the sideline. As it turns out, not only is this solid advice as it keeps your opponent guessing whether you will offload the ball, but it will protect your ECU tendon and subsheath as well. Running with the ball cradled against your chest places your wrist in the ECU danger position, and add in the forceful isometric ECU contraction at contact in a tackle and you are at high risk of ECU injury.

 
 

Subjective Examination — What they say

As always, a thorough subjective examination should reveal all. You also want to consider all differential diagnoses for ulnar-sided wrist pain, including TFCC injury, DRUJ instability, lunotriquetral ligament/joint injury, proximal carpal row instability, ulnar styloid fractures and carpal osteoarthritis if the player advanced in age (15). Other common occurring injuries, especially in golf and tennis include: extensor and flexor tendinitis, ulnar carpal impingement, De Quervains Tenosynovitis, hook of hamate fractures and ‘intersection syndrome’ (involving the thumb tendons APL ad EPB) (13, 16).

ECU Subluxation

Players will report an unexpected pop or snap when striking the ball (6). They will likely have a history of repetitive overuse (15). If it is an acute-traumatic case, there may be excruciating pain and concurrent TFCC injury is also likely. They may or may not have pain following play.

ECU subluxation may also be completely asymptomatic and may not require treatment, in which case attention should shift to surrounding structures (4).

Players may be able to force dislocation of the ECU tendon with active wrist flexion with or without ulnar deviation in forearm supination (2).

(Warning: as I found out by repeatedly testing my own subluxing tendon whilst writing this piece, if you test an asymptomatic ECU subluxing tendon too much, it will become symptomatic due to acute swelling. Haha! In my case I lost power and had a pain-free snap with forehands at the following training session…which was also a wet session, see ‘player ‘quick tips’ above about the dangers of playing in the wet with heavy balls.)
ECU Tendinopathy

Players may report that the pain has developed gradually, there is no history of acute trauma or a fall. Players may report that the wrist is painful during warm-up but then it goes away. They may also report a change in string tension (see tennis-specific section above, ECU tendon aggravated by increased string tension, too much, too soon. It requires the player to apply more top spin). They may report and increase in their acute workload which exceeds their chronic workload (see recent articles on acute/chronic workload by Gabbet & Blanch (17–19)).

ECU Tenosynovitis

As tennis players don’t commonly get ECU tenosynovitis there’s no research I could find on reported symptoms during training and matches. However, given the symptoms of the normal population experiencing this condition, I’d suggest that during the acute/early stage, any wrist movements will be highly aggravating, similar to De Quervains Tenosynovitis.

ECU Tendon Rupture

The player will report an initial accident with recurring pain and trial periods of rest and painful play. Players with ECU rupture in one study had two players with complete rupture who had corticosteroid injections before the rupture occurred (6), but one can only speculate if this led to the rupture or whether the players tendons were about to go anyway, still it warns of caution when injecting corticosteroids around tendons. Players may report having no problems with forehands, but they will lack power with their double-handed backhand, and repeated microtrauma to the tendon by continuing play eventually leads to total failure (6).

Objective Examination — ‘ what you see’

ECU Tendionpathy & Tenosynovitis

There may be tenderness on palpation along the ECU tendon pathway from the insertion on the 5th metacarpal. Resisted active extension and ulnar deviation should also aggravate the ECU. There may also be pain with resisted supination (6). There may be visible swelling over the ulnar head. Acute tenosynoviits may be painful with minimal wrist ROM testing.

ECU Subluxation

To reproduce subluxation place the wrist in maximal flexion and ulnar deviation and then ask the player to actively supinate (4), however there may also be pain in pronation (15).

ECU Special Tests

The ECU Synergy Test (20):

Described two ways:

  1. Elbow resting in table, elbow flexed to 90deg. Wrist supinated, fingers extended. Examiner holds middle finger and thumb adducted with one hand, and palpates the ECU tendon with the other hand. Player asked to force the thumb into abduction. The test is positive if there is pain and/or subluxation of the ECU tendon.
  2. Patient holds hands up with thumbs in. Patient applies forcefull isometric abduction between thumbs. The test is positive if there is ulnar sided pain and/or subluxation of the ECU tendon.
 

An alternative ECU Synergy test can be seen on this video (skip to 12min24sec): https://youtu.be/GRxY6ghU3eg?t=12m24s

The Ice Cream Scoop Test (21):

  • Ask the patient to simulate the action of scooping ice cream. Repeat against resistance with palpation of the ECU tendon. The test is positive if there is a visible, audible or palpable snapping of the ECU tendon.
 
 

Diagnostic Imaging — What’s going on inside?

 
ECU sheath under ultrasound

Ultrasound (US) can be used to dynamically assess tendon subluxation. One operator can test the ECU tendon whilst the other performs the US (6). US may also find a vascularised tendon sheath which would suggest tenosynovitis. Doppler imaging may find tendon neovascularisation (4, 6). If there is no instability of the ECU tendon, there may be fluid around the tendon and tendon thickening, especially if it is an acute episode(16).

 
US of ECU tendon in pronation and supination

3-T MRI can be used to assess the ECU subsheath damage and also to rule out/in concurrent DRUJ or TFCC injuries. There will normally be increased SI (signal intensity) around ECU tendons with acute tendinopathy. MRI will also be used to confirm complete tendon rupture, with acute rupture there will be adjacent soft-tissue haemorrhage and the terminal tendon may or may not be present depending on the degree of retraction, with chronic rupture, there will simply be no tendon.

 
 
MRI of ECU subsheath

Treatment — What we’ll do about it

Education

Our most valuable treatment tool. If you haven’t discussed any of the below, they’ll probably be back in 3–6months. Cover the intrinsic and extrinsic factors that led to the injury, hopefully you can also get this information to the coach/parent too. Reinforce the kinetic chain, use any downtime (upper limb rest) to work on lower limb plyometrics, stability, strength and power.

 

ECU Tendinopathy & Tenosynovitis

 

Acute/Reactive tendinopathy will respond well to rest, activity modification and a thermoplastic or pre-fab splint (pictured above) http://www.djoglobal.com/products/exos/wrist-brace-boa) for 3weeks minimum (wrist extension splint approx. 15–30deg) (6).

A long-arm splint (pictured below) instead of a forearm-based splint can also to be used to ensure pronation if it helps the player, however there is little evidence to split the two (4).

It is important that the aggravating activity is addressed and to reduce ECU injury recurrence in the future. It is vital that the aggravating technique is adjusted. If you are unsure of the technique for whatever sport it is, ask the player or bring the coach into the next appointment. With the coach and the player both on board, home exercise program compliance will drastically improve. It also does wonders in improving coach-physio relations in general, which is always a good thing.

In the clinic, I use passive ultrasound over the tendon and massage (combined with heat) on the forearm extensor muscles as an opportunity to discuss the symptoms and overall plan with the client.

Once the pain has settled, load management is critical. Ensure the athlete employs a new technique that isn’t aggravating and gradually increases their weekly training load, again with athletes managed by a coach or parent, liaison with the coach or parent is vital for long-term compliance.

Once you have load management and technique covered, you can commence wrist stabilisation exercises, wrist and grip strengthening followed by global upper limb and trunk strength & conditioning.

Chronic/Dysrepair tendinopathy will take longer to resolve. Although eccentric exercises for chronic tendinopathies have been shown to have good effect in the lower limb (Achilles and patella tendons), they are yet to be shown to be effective in the upper limb. Resisted isometric exercises and wrist stability exercises can be effective.

US-guided (to avoid tendon contact) steroid injection into the fibro-osseus sheath can be considered. Surgical compartment release may also assist for persistent cases, especially if there is a stenosing tenosynovitis, although this is rare (22).

ECU Tendon Instability/Subsheath Rupture

For acute traumatic unstable ECU tendon injuries, 6 weeks immobilisation of the wrist with the tendon reduced is recommended. The subluxed ECU tendon can be repositioned in the ulnar groove with the wrist in radial deviation and pronation. Tennis players with acute ECU tendon subluxation have been successfully treated conservatively by being placed in in long-arm casts for up to 4 months (6), this obviously impacts on player strength & conditioning so a short-arm splint may be favoured instead. As with the tendinopathy, a pre-fabricated or thermoplastic wrist extension splint (15–30o) is recommended.

For the elite athlete a monthly combined MRI and US imaging should be recommended to check for ECU subsheath healing and the tendon is re-inserting into the ulnar groove. After 8 weeks, the ECU tendon should be tested.

ECU Tendon Instability/Subsheath Rupture

For acute traumatic unstable ECU tendon injuries, 6 weeks immobilisation of the wrist with the tendon reduced is recommended. The subluxed ECU tendon can be repositioned in the ulnar groove with the wrist in radial deviation and pronation. Tennis players with acute ECU tendon subluxation have been successfully treated conservatively by being placed in in long-arm casts for up to 4 months (6), this obviously impacts on player strength & conditioning so a short-arm splint may be favoured instead. As with the tendinopathy, a pre-fabricated or thermoplastic wrist extension splint (15–30o) is recommended.

For the elite athlete a monthly combined MRI and US imaging should be recommended to check for ECU subsheath healing and the tendon is re-inserting into the ulnar groove. After 8 weeks, the ECU tendon should be tested.

  • If the ECU tendon is stable, a graduated wrist stability program should take place for the next 4 weeks with a return to gradual upper body strength and conditioning. At week 12, the player can return to sport.
  • If the ECU tendon is still unstable, splint for another month, and remind the player to avoid supination movements.

Montalvan et al. (2006) found that 3–4 months immobilisation was sufficient to allow complete and stable healing of the ECU subsheath. However, surgical repair of the ECU subsheath followed by 3–5 weeks of immobilisation can also be considered, but in my humble & limited hands experience in our hands clinic, post-surgical wrists can often present with some long-term loss of range of movement.

ECU Surgery

For chronic subluxation, extensor compartment reconstruction surgery may be indicated. Surgeons will differ in their repair of the ECU subsheath. The most common treatment utilises flaps of the extensor retinaculum to reinforce the ECU subsheath (16), some will simply reattach two ends of the subsheath (if they exist, and are in good enough condition), if type C (periosteum detachment with false pouch) the periosteum will be reattached with transosseus sutures or anchor sutures. Some surgeons may choose to deepen the ulnar groove (11).

Below pics from: Inoue G, Tamura Y. Surgical treatment for recurrent dislocation of the extensor carpi ulnaris tendon. Journal of Hand Surgery (British and European Volume). 2001;26(6):556–9.

Type A

Type A

 

Type B

 

Type C

 

Post-op, the wrist will be immobilised in a splint (preferably thermoplastic) for a 3–6 weeks (16) before gentle ROM, grip strength and wrist stabilisation exercises will commence. Wrist stabilisation exercise will then progress and become more specific to the player. There is not much literature here (but see Elisabet Hagert’s article (2010) for a proposed protocol for wrist proprioception training (23)), slosh pipes and the like can be used, I would even start heading down a pathway involving a racquet with some therabands attached to it with sustained slow holds going from pronation to supination over 30seconds or something similar. If you see any nice protocols with slosh pipes, please send them my way. They are cheap to make and I’ve had positive results thus far with proximal carpal row instability with 3x20secs x3/day of slow side to side movement progressing from short lever arm to long lever arm in pronation (pipe = 1m pvc with 1L water, capped at both ends).

ECU Tendon Rupture

Surgery may be required if the player relies on their double handed backhand in order to compete. The palmaris longus tendon will be used to reconstruct the ECU tendon, and the 6th compartment will also be reconstructed. Studies report success with this operation and player returned to high level tennis after 6 months (6). 

Food for thought — I’m looking for research on:

Due to the high bounce of the clay court, does the clay-court season in elite tennis (culminating in the French Open) have a higher incidence of wrist injuries?

If so, an idea for players at risk (western grips, kinetic chain problems elsewhere) would be to wean into the ‘wrist risky’ season by reducing string tension and adopting a slightly more eastern-direction grip (western->semi western, semi-western-> continental) for the first few weeks of the season and then work back into normal string tension and grips. Also the player should really focus on their leg drive during the clay court season or work hard sticking to the baseline to take the balls low before they rise to high. 

Quick tips for tennis players/coaches for tennis wrist injuries:

  • Repetitive hitting of balls at or above chest height increases risk of wrist injury.
  • Use your legs to get low and explode up and hit through the ball.
  • Change to a continental grip for a short time to reduce irritation to the wrist. Thumb-sided wrist pain often occurs with eastern grips, little-finger-sided wrist pain often occurs with western/semi-western grips.
  • Watch your load on different court surfaces, make sure you provide your body time to adjust to different court surfaces, similar to acclimatising when travelling.
  • When changing string tensions, do so in small increments over weeks, as sudden change will result in tendon overload, especially in your upper limbs.
  • If you feel a wrist popping during forehands, adopt a more continental/eastern grip if you are drilling forehands.
  • Don’t train with wet/heavy balls. Small changes in ball weight can overload your upper limb tendons as they have to develop more power to counteract the change in weight.
  • In training, mix up single handed and double handed backhands. Work on tactical play with a single handed slice if you are symptomatic for an acute ECU tendon subluxation.
  • Try a combination of the following during acute wrist pain episodes: Decrease string tension, ​Decrease racquet weight, Train on grass or hard court, ​Adopt more continental/eastern grip, Apply external wrist support

Seek guidance from a Hand Therapist early if you have many tournaments coming up and you have wrist pain. The earlier you pick up on hand injuries, the far easier they are to treat. Don’t get stuck in the ‘vicious cycle of adaptation and injury’.

Quick Tips for therapists dealing with tennis wrist injuries

  • Differentiate between ECU tendinopathy, subluxation, complete rupture and tenosynovitis.
  • Ensure there are no other concurrent ulnar-sided wrist pathologies (eg: TFCC) as this will greatly affect recovery time.
  • Listen to the player and/or coach/parent, ask them about their tournament schedule/calendar, find out which tournaments are high priority and low priority. You might find that there are low priority tournaments that they can miss in order to be “100%” for the important ones.
  • Stock up with pre-fabricated wrist extension splints, they are handy for acute ulnar-sided wrist pathology and save you making a thermoplastic splint each time.
  • If you get the opportunity, find a good US operator and offer to come along to the US appointment with your client in order to perform the ECU tendon instability test whilst the US operator images the wrist.
  • When treating tennis players, you must consider extrinsic and intrisic factors. Such as: court surface changes, injuries elsewhere in the kinetic chain, string tension changes, string type changes, training programming, load programming and racquet changes (weight change). Refer to the “USTA Tennis Technique and injury Prevention White Paper.
 
 

References

1. Wijffels M, Brink P, Schipper I. Clinical and non-clinical aspects of distal radioulnar joint instability. The open orthopaedics journal. 2012;6:204.

2. Inoue G, Tamura Y. Recurrent dislocation of the extensor carpi ulnaris tendon. British journal of sports medicine. 1998;32(2):172–4.

3. Salva-Coll G, Garcia-Elias M, Leon-Lopez M, Llusa-Perez M, Rodríguez-Baeza A. Role of the extensor carpi ulnaris and its sheath on dynamic carpal stability. Journal of Hand Surgery (European Volume). 2012;37(6):544–8.

4. Campbell D, Campbell R, O’Connor P, Hawkes R. Sports-related extensor carpi ulnaris pathology: a review of functional anatomy, sports injury and management. British journal of sports medicine. 2013;47(17):1105–11.

5. Jeantroux J, Becce F, Guerini H, Montalvan B, Le Viet D, Drapé J-L. Athletic injuries of the extensor carpi ulnaris subsheath: MRI findings and utility of gadolinium-enhanced fat-saturated T1-weighted sequences with wrist pronation and supination. European radiology. 2011;21(1):160–6

6. Montalvan B, Parier J, Brasseur J, Viet D, Drape J. Extensor carpi ulnaris injuries in tennis players: a study of 28 cases. British journal of sports medicine. 2006;40(5):424–9.

7. Lee KS, Ablove RH, Singh S, De Smet AA, Haaland B, Fine JP. Ultrasound imaging of normal displacement of the Extensor Carpi Ulnaris tendon within the ulnar groove in 12 forearm–wrist positions. American Journal of Roentgenology. 2009;193(3):651–5.

8. Iida A, Omokawa S, Moritomo H, Aoki M, Wada T, Kataoka T, et al. Biomechanical study of the extensor carpi ulnaris as a dynamic wrist stabilizer. The Journal of hand surgery. 2012;37(12):2456–61.

9. León-Lopez MM, Salvà-Coll G, Garcia-Elias M, Lluch-Bergadà A, Llusá-Pérez M. Role of the extensor carpi ulnaris in the stabilization of the lunotriquetral joint. An experimental study. Journal of Hand Therapy. 2013;26(4):312–7.

10. Brigstocke G, Hearnden A, Holt CA, Whatling G. The functional range of movement of the human wrist. Journal of Hand Surgery (European Volume). 2013;38(5):554–6.

11. Stathopoulos IP, Raptis K, Ballas EG, Spyridonos S-PG. Recurrent Dislocation of The Extensor Carpi Ulnaris Tendon in a Water-Polo Athlete. Trauma monthly. 2016;21(1).

12. Inoue G, Tamura Y. Surgical treatment for recurrent dislocation of the extensor carpi ulnaris tendon. Journal of Hand Surgery (British and European Volume). 2001;26(6):556–9.

13. Tagliafico AS, Ameri P, Michaud J, Derchi LE, Sormani MP, Martinoli C. Wrist injuries in nonprofessional tennis players: relationships with different grips. The American journal of sports medicine. 2009;37(4):760–7.

14. Cook J, Purdam CR. Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British journal of sports medicine. 2009;43(6):409–16.

15. Futami T, Itoman M. Extensor carpi ulnaris syndrome: Findings in 43 patients. Acta orthopaedica Scandinavica. 1995;66(6):538–9.

16. Watanabe A, Souza F, Vezeridis PS, Blazar P, Yoshioka H. Ulnar-sided wrist pain. II. Clinical imaging and treatment. Skeletal radiology. 2010;39(9):837–57.

17. Blanch P, Gabbett TJ. Has the athlete trained enough to return to play safely? The acute: chronic workload ratio permits clinicians to quantify a player’s risk of subsequent injury. British journal of sports medicine. 2016;50(8):471–5.

18. Gabbett TJ. The training — injury prevention paradox: should athletes be training smarter and harder? British journal of sports medicine. 2016;50(5):273–80.

19. Gabbett TJ, Hulin BT, Blanch P, Whiteley R. High training workloads alone do not cause sports injuries: how you get there is the real issue. British journal of sports medicine. 2016;50(8):444–5.

20. Ruland RT, Hogan CJ. The ECU synergy test: an aid to diagnose ECU tendonitis. The Journal of hand surgery. 2008;33(10):1777–82.

21. Ng CY, Hayton MJ. Ice cream scoop test: a novel clinical test to diagnose extensor carpi ulnaris instability. The Journal of hand surgery, European volume. 2013;38(5):569–70.

22. Hajj AA, Wood MB. Stenosing tenosynovitis of the extensor carpi ulnaris. The Journal of hand surgery. 1986;11(4):519–20.

23. Hagert E. Proprioception of the wrist joint: a review of current concepts and possible implications on the rehabilitation of the wrist. Journal of Hand Therapy. 2010;23(1):2–17.