Flexor-Pronator Mass Strain / Tendinopathy

Because in a throwing athlete the medial elbow harbours a triad of overlapping problems - flexor-pronator strain or tendinopathy, ulnar collateral ligament injury, and ulnar neuritis - that frequently coexist, and treating an apparent flexor-pronator strain while missing UCL insufficiency will fail. The flexor-pronator mass is the common flexor origin from the medial epicondyle and acts as a dynamic stabiliser against valgus stress, backing up the UCL, so the repetitive valgus loads of throwing stress both the muscle origin and the ligament together; importantly, this dynamic protection is position- and load-dependent and may not be as protective during the very high valgus of pitching as once believed. So I would assess the medial elbow comprehensively rather than stopping at the flexor-pronator: provocative resisted wrist-flexion and forearm-pronation testing and tenderness mapping for the flexor-pronator; valgus stability testing, such as the moving valgus stress test, with MRI or MR-arthrography for the UCL; and ulnar nerve assessment with Tinel's and nerve conduction. Most isolated flexor-pronator injuries - strain or medial epicondylitis - respond to non-operative management: relative rest, eccentric and progressive loading rehabilitation and NSAIDs, with corticosteroid injection used cautiously because of the tendon-weakening risk, and surgery, debridement with or without repair, reserved for refractory cases. But if there is underlying UCL insufficiency, the dynamic stabiliser cannot compensate for an incompetent ligament, and the pitcher will not return to throwing until the ligament is addressed, potentially with reconstruction. So the key is not to treat the flexor-pronator in isolation.