The common flexor tendon (CFT) attaches to the medial epicondyle of the humerus and the anterior bundle of the ulnar collateral ligament (UCL). The CFT is composed of the tendons of the following 5 muscles:
- Flexor carpi radialis (FCR)
- Flexor carpi ulnaris (FCU)
- Flexor digitorum superficialis (FDS)
- Pronator teres (PT)
- Palmaris longus
Causes / typical injury mechanism: Medial epicondylitis presents as insidious or acute medial elbow pain that is worsened by repetitive wrist flexion, forearm pronation, and valgus overload on the elbow.
Classic history and presentation: This mechanism is most commonly work related and can be seen in manual labor occupations such as construction, plumbing, and carpentry. It is also observed in athletes who participate in baseball, golf, tennis, football, weightlifting, and bowling. In throwers, medial epicondylitis is exacerbated during the late cocking or early acceleration phase. This condition classically presents after repetitive use with medial pain at the elbow.
- Age – Often seen in the 4th through 6th decades of life.
- Sex / gender – Equally affects men and women.
Pathophysiology: Degeneration begins at the common flexor origin when this repetitive trauma causes peritendinous inflammation. Histologically, angiofibroblastic hyperplasia is observed as vascular and fibroblastic elements invade the tendon. Ultimately, this results in hyaline degeneration and irreparable fibrosis / calcification of the flexor-pronator musculotendinous mass.