One source of shoulder pain can be myofascial trigger points (MTrPs). MTrPs are localized,
hyperirritable points in the skeletal muscles that are associated with palpable nodules in
muscle fibres. MTrPs can be classified into active and latent. Latent MTrPs demonstrate the
same clinical characteristics as active MTrPs but they do not provoke spontaneous pain.
Numerous studies have shown that MTrPs are prevalent in patients with chronic non-traumatic
neck and shoulder pain.