(Sometimes referred to as 'fibrositis') are very common and related to back pain. They occur in the neck or shoulders (often caused by bad posture or stress) or sometimes in the sacroiliac region at the base of the spine. Painful 'knots' form within muscles which have gone into spasm - a reaction which the body triggers in order to tighten muscles round a problem area to prevent further injury. This is why the condition so often occurs in patients who have had a back pain problem for some time.
Your chiropractor will therefore use manipulation to adjust the relevant joint, but also deep massage and soft tissue work to relieve the condition. Since the 'knots' of muscle are often very tender, the soft tissue treatment may be painful at first.