Wrist extensor muscle pathology in lateral epicondylitis

The morphology of the extensor carpi radialis brevis (ECRB) muscle was inve stigated in 20 patients with longstanding lateral epicondylitis. Muscle bio psies were obtained from the proximal or distal portion of the ECRB and ana lysed by enzyme- and immunohistochemical methods. Morphological abnormaliti es were significantly more frequent in patients than controls and included moth-eaten fibres, fibre necrosis and signs of muscle fibre regeneration as well as higher percentages of the fast-twitch oxidative (type 2A) fibre ty pe. Changes were equally distributed proximally and distally, It is conclud ed that these changes, directly or indirectly, mag reflect the cumulative e ffect of mechanical and/or metabolic overload and that decreased muscular p erformance in patients with lateral epicondylitis may be due to both elbow pain and physical damage to the ECRB muscle.