Firstly they can happen when the muscle has a direct impact. Falling, tripping, wrenching, car collisions, muscle tears or sprains, dislocations are all reasons they can occur. Any kind of brace, slings or casts used after operations are also reasons for trigger points. Injections into muscles can set up trigger points, the gluteal muscles being particularly susceptible, leaving people with a mysterious agonizing case of sciatica for some time afterwards.
Postural habits, repetitive movements, poor work habits, lack of exercise, can all be reasons for trigger points.
Trigger points are often gone unsuspected and unaddressed, yet are a major source of pain for many people. Deep tissue massage can eliminate trigger points and hence address chronic myofascial pain.