The flexor digitorum profundus muscle is found in the front of the forearm. It can contribute to pain and twitching in the four fingers. It can affect one or any combination of the fingers. It can also cause trigger finger, where a finger will lock in a bent position.
The flexor digitorum superficialis is located in the front of the forearm. It contributes to pain in the four fingers, the palm, and occasionally the wrist. The muscle is a major contributor to trigger finger.
The palmaris longus muscle contributes to pain in the wrist, the palm of the hand, and will sometimes extend up into the forearm.
The flexor carpi ulnaris muscle is located on the inside (pinky side) of the forearm. It contributes to pain in the wrist, palm of the hand, and the ring and little fingers. Pain is sometimes felt in the elbow.
The flexor carpi radialis muscle is located in the front of the forearm. It contributes to pain in the wrist, bottom of the palm that often extends to the thumb pad and thumb. Twisting the wrist and gripping objects is painful.
The flexor hallucis longus can cause and contribute to pain in the big toe and ball of the foot. A classic sign of flexor hallucis longus dysfunction is numbness on the bottom of the big toe.
The flexor digitorum brevis muscle is located on the bottom of the foot. It can cause a sharp stabbing pain in the ball of the foot that becomes a deep ache when resting.
The pronator teres muscle is located in the front of the forearm. It can contribute to pain in the wrist near the thumb. Pain is often felt in the thumb pad and can extend up into the forearm. Cupping the hand can become almost impossible because of intense pain in the wrist and or thumb pad.
The flexor hallucis brevis muscle contributes to pain on the bottom of the foot, just under the big toe. It can also be a factor in plantar fasciitis, hammer toe, turf toe and gout.