Definition

Stress injury to the ulnar (medial) collateral ligament of the elbow joint caused by repeated, intense throwing movements. This is a typical sports injury; it mainly affects baseball pitchers, but the injury is also known to occur in American football, volleyball, tennis and javelin throwing. The acceleration of the arm during the throw consists of a wind-up, the actual throwing motion and the stop. Particularly during the transition from the dorsal wind-up to the ventral throw, there is significant stress on the lig. collateral ulnar ligament (MCL), as the trunkohumeral and scapulohumeral muscles reverse the upper arm from a backward movement to a forward movement and from exorotation to internal rotation, whilst the forearm, with its inertia and the thrown object, only follows the movement of the upper arm with a delay.
For the Lig. collateral ulnar ligament, a load-bearing capacity is specified that corresponds to a valgus moment of approximately 33 Nm; however, in sports, torques or impulses of over 60 Nm in some cases occur. For the medial elbow, shear forces of up to 300 N are calculated; for the lateral elbow, compressive forces of up to 500 N. Muscles such as the palmar flexors of the wrist, finger flexors and the pronator teres are unable to adequately absorb these forces, resulting over time in ligamentous insufficiency of the MCL with medial gapping, i.e. the joint giving way in the valgus direction. This, in turn, impairs force distribution within the joint and can lead to osteoarthritis with the formation of osteophytes. The ulnar nerve may also be affected by medial gapping. The development of golfer’s elbow due to the compensatory action of the forearm muscles originating from the medial epicondyle is also possible. Further complications may include the formation of loose bodies and, where applicable, radiocapitellar osteochondral lesions resulting from lateral compression. Furthermore, medial apophysitis of the medial epicondyle (94% in one study), as well as with repeated forceful hyperextensions of the elbow joint osteophyte formation at the olecranon and stress fractures of the olecranon.
It appears that changes to throwing technique cannot necessarily solve the problem, as they can only reduce the stress, whilst the factor of repetition remains an important contributing component.

Throwers often develop changes in the shoulder joint alongside pitcher’s elbow, such as increased external rotation due to laxity of the joint capsule and reduced internal rotation due to bony adaptations and thickening of the dorsal joint capsule.

cause

1. Repeated vigorous throwing movements

Predisposing

1. existing valgus instability

Diagnosis

1. Tests and manoeuvres: Valgus stress test, Milking manoeuvre, Moving valgus stress test

Symptoms

1. asymptomatic at the outset
2. pain on the inside of the elbow when throwing
3. instability with medial gapping, sometimes asymptomatic

Complications

1. Golfer’s elbow
2. lateral osteoarthritis of the elbow joint
3. Irritation of the ulnar nerves
4. free bodies
5. traction apophysitis
6. radiocapitellar, osteochondral lesions
7. osteophyte formation at the olecranon

Therapy

1. Stress reduction

External links:

https://www.germanjournalsportsmedicine.com/fileadmin/content/archiv2017/Heft_10/Uebersicht_Nietschke_Ellenbogeninstabilitaeten_10-2017.pdf
https://www.drronakpatel.com/wp-content/uploads/2023/01/17-The-Thrower_s-Elbow.pdf