Sometimes my middle finger starts twitching all by itself. When I press on my forearm, it stops but there is a lot of pain there. What could be causing this kind of reaction?

You may have pinpointed an active trigger point (TrP) in a muscle. What you are seeing is called a twitch response. Trigger points are described as hyperirritable spots in a muscle. They are accompanied by nodules you can feel in taut bands of muscle fibers.

These pea-sized nodules are said to be small knots of contracted tissue. In a constantly contracting muscle there isn’t the normal massaging contract-relax response. Waste products from cellular metabolism start to build up. Pain is the final result.

The local twitch response you’re seeing is not the same as a muscle spasm. This is because a muscle spasm refers to the entire muscle contracting at one time and staying contracted. The local twitch response only involves a small twitch of the muscle – not a full contraction.

The mechanism of trigger points remains a matter of hot debate. Immobilization of muscles (e.g., in a cast or splint) and repetitive overuse seem to be two risk factors. With treatment, that twitch and the muscle pain can both be eliminated. A physical therapist can help you by treating the TrPs to eliminate the painful symptoms and the local twitch response you are having.