Lateral Epicondylitis (Tennis Elbow)
Degenerative enthesopathy of the common extensor origin at the lateral humeral epicondyle, a frequent cause of lateral elbow pain.
Overview
Lateral epicondylitis is a degenerative tendinopathy of the common extensor origin, particularly the extensor carpi radialis brevis (ECRB). Despite the suffix, histology shows angiofibroblastic hyperplasia without inflammatory cells, more accurately termed a tendinosis. Repetitive wrist extension and forearm supination are implicated, in sport and in occupational settings.
Epidemiology
Annual incidence is around 1 to 3 percent of the general population, peaking between 40 and 60 years with no sex predilection. Only a minority of cases arise from tennis, despite the eponym.
Symptoms
Patients describe lateral elbow pain radiating into the forearm, worse with gripping, lifting, and resisted wrist extension. Pain on resisted middle finger extension (Maudsley test), resisted wrist extension with elbow extended, and tenderness just distal to the lateral epicondyle are diagnostic.
Imaging
Diagnosis is clinical. Ultrasound and MRI can confirm tendon changes and exclude differentials (radial tunnel syndrome, posterolateral rotatory instability, synovial plica, osteoarthritis). Imaging is reserved for atypical or refractory cases.