common extensor tendon common extensor tendon the common extensor tendon is a tendon that attaches to the lateral epicondyle of the humerus. common extensor tendonidentifiersta22498fma0326751anatomical terminology structure the common extensor tendon serves as the upper attachment (in part) for the superficial muscles that are located on the posterior aspect of the forearm: extensor carpi radialis brevis extensor digitorum extensor digiti minimi extensor carpi ulnaris the tendon of extensor carpi radialis brevis is usually the most major tendon to which the other tendons merge. function the common extensor tendon is the major attachment point for extensor muscles of the forearm. this enables finger extension and aids in forearm supination. clinical significance lateral elbow pain can be caused by various pathologies of the common extensor tendon. overuse injuries can lead to inflammation. tennis elbow is a common issue with the common extensor tendon.