common flexor tendon common flexor tendon the common flexor tendon is a tendon that attaches to the medial epicondyle of the humerus (lower part of the bone of the upper arm that is near the elbow joint). common flexor tendonidentifiersta22489fma63259anatomical terms of muscle it serves as the upper attachment point for the superficial muscles of the front of the forearm: flexor carpi ulnaris palmaris longus flexor carpi radialis pronator teres flexor digitorum superficialis