3.0 AETIOLOGY
The formation of TrPs in the lower extremity can be in response to a single inciting event or repetitive microtrauma. They commonly arise as a secondary phenomena to lateral ankle sprains and acute knee injuries, or following overuse pathology and the development of antalgic patterns of gait (Fomby, 1997).Biomechanical abnormalities can lead to an increase in stress on the musculoskeletal system and promote the formation and perpetuation of TrPs (Fomby, 1997). These abnormalities may include the compensations for a limb length discrepancy, abnormal subtalar joint pronation or a hallux limitus. It is the author's belief that increases in the contact phase velocity and degree of subtar joint pronation could lead to TrPs in tibialis anterior and tibialis posterior. A hallux limitus could result in an unstable medial column during late midstance and propulsion and in theory lead to TrP formation in peroneus longus and/or the intrinsic musculature. Similarly, an ankle equinus could result in the development of TrPs in the superficial deep and anterior compartment musculature.
Other causes or precipitating factors include poor work ergonomics leading to muscle overuse, stress and various rheumatological conditions. Metabolic disorders related to thyroid, parathyroid, oestrogen, cortisol and adrenal abnormalities have also been implicated (Sonkin, 1994).
