OK sign to assess median nerve

The OK sign evaluates the anterior interosseous branch of the median nerve by evaluating flexion at the distal interphalangeal (DIP) joint and testing the strength of the flexor pollicis longus and flexor digitorum profundus. The patient is asked to make the OK sign and then maintain it against resistance (pictured above). Patients with anterior interosseous nerve deficits will have flattening at the DIP joint and weakness of the muscles of apposition.