People easily adapt to this weakness without conscious effort or self-awareness, by using 1) the next muscles down, which are innervated by a different nerve, or 2) using ligaments to give resistance, pinching laterally against the index finger or against the side of the end of the thumb, or 3) by what is called "tenodesis," which in this case is extension of the wrist joint, which tightens the muscles on the palm side of the hand.

These adaptations on a moment-to-moment basis do not cause problems, but over time in loose-jointed patients, such as many women and people with collagen disorders such as Ehlers Danlos Syndrome, the adaptations can cause soft tissue failures that can become painful, particularly at the base of the thumb and in the proximal forearm (i.e., "Tennis Elbow" in a non-tennis player).

In the proximal forearm it gives rise to the anterior interosseous nerve which innervates the flexor of the thumb (FPL), the flexor digitorum profundus of the index finger (FDP IF), and the pronator quadratus, and terminates in a sensory branch to the bones of the wrist, i.e., the carpal tunnel.

The most common chief complaint is intermittent pain in the wrist, associated with sustained pronation, frequently misinterpreted by patients and providers as "tendonitis."

[11][12] The flexor pollicis longus and FDP of the index finger are weak, leading to impairment of pinching firmly.

[20] Although MRI may show denervation atrophy of the affected muscles, its role in the evaluation of pronator teres syndrome is unclear.