Knee muscle activity during ambulation of trans-tibial amputees

Gait analysis of trans-tibial amputees brings to light asymmetries of diffe rent gait parameters between the amputated and sound legs. The present stud y investigated the activity of the vastus medialis and biceps femoris muscl es during ambulation of trans-tibial amputees. Peak activities of the vastu s medialis were reached similarly in both legs (6.06 +/- 4.9 % and 8.84 +/- 3.6 % of gait cycle, in the sound and amputated leg, respectively). Biceps femoris peak activities were reached at 92.43 +/- 6.6 % of gait cycle in t he sound leg, and significantly later (at 9.81 +/- 4.8 % of gait cycle) in the amputated leg (p < 0.05). Integrated EMG activity ratios, between swing and stance periods, were similar for the vastus medialis (0.33 in the soun d and 0.35 in the amputated leg). However, these ratios differed significan tly for the biceps femoris since the amputated leg presented a substantial (p < 0.05) smaller ratio (0.22) compared with the sound leg (0.83). The use of prosthesis in trans-tibial amputees requires further activity of the bi ceps femoris during stance period to improve support of the amputated leg k nee joint.