The Science of Tennis Elbow

Lateral epicondylalgia (tennis elbow) is a degenerative tendinopathy affecting the common extensor tendon origin at the lateral epicondyle, primarily involving the extensor carpi radialis brevis (ECRB) tendon. Despite the name, fewer than 10% of cases occur in tennis players. The condition is characterized by a failed healing response resulting in angiofibroblastic degeneration rather than acute inflammation. The pathophysiology begins with repetitive mechanical overload of the wrist extensors exceeding the tendon's adaptive capacity. This leads to microtears, disorganized collagen structure, increased ground substance, neovascularization, and neurogenic inflammation. Histologically, the tissue shows angiofibroblastic hyperplasia with absence of inflammatory cells, confirming this is tendinosis rather than tendinitis. The ECRB is particularly vulnerable due to its anatomical position and biomechanical demands. It originates from a small area on the lateral epicondyle and must generate force across both the elbow and wrist joints. During gripping and wrist extension activities, the ECRB experiences high tensile loads, especially with the elbow extended and forearm pronated - the exact position used during computer work and manual labor. Neurogenic sensitization occurs in chronic cases, with elevated substance P and calcitonin gene-related peptide in the affected tendons. This contributes to pain amplification and may explain why some cases become recalcitrant to treatment. The condition often coexists with cervical radiculopathy and shoulder dysfunction, as neural and biomechanical factors from proximal regions can perpetuate or exacerbate symptoms. Risk factors include age 40-50 years (peak incidence), occupations requiring repetitive gripping and wrist extension (construction, manual labor, computer work), poor wrist posture, inadequate forearm strength, and sudden increases in hand-intensive activities. Similar to golfers elbow (medial epicondylalgia), this represents failed tendon healing, though it affects the lateral rather than medial elbow and involves different muscle groups.