Sprained Ankle Pain Model
Ankle sprain commonly occurs during participation in various strenuous sports, as well as during routine locomotive activity, and is a common source of persistent pain and reduction of mobility. The rat model of sprained ankle pain is produced by manually over-extending the lateral ligaments, without breaking them, to imitate a lateral ankle sprain in a human. The ankle sprain rat subsequently showed swelling of the ankle and a reduced stepping force of the affected limb for the next several days. The amount of reduction of foot stepping force is used as an index of the degree of pain generated by ankle sprain.
The typical ankle sprain is caused by a combination of forces that tend to adduct, invert and plantar flex the talus beyond its physiological limit (Connolly 1981). Such motion causes avulsion of lateral ligaments, rupture of the adjacent capsule, and soft tissue hemorrhage and edema, resulting in severe discomfort and