The Effects of Bracing and Knee Flexion Angle on Hamstring Activity During Crutch Walking: A Preliminary Study for Post-Operative Care

Objectives:  To determine if immobilization of the knee at varying degrees of knee flexion will limit the surface electromygraphical (sEMG) activity of hamstring muscles during crutch-assisted ambulation.  Methods:  Ten healthy participants walked with crutches with the knee maintained at 0, 30, 60 and 90° of knee flexion, both with and without a brace. The leg was non-weight bearing for all trials except for those with the knee at 0° of flexion, when subjects performed a ‘toe-touch’ gait. sEMG was used to record activity of the biceps femoris and semitendinosus during trials.  Results:  For the semitendinosus, there were no differences between braced and unbraced conditions at 0° (22.5 vs. 23.2%), 30° (37.5 vs. 28.7%), 60° (47.2 vs. 44.6%), and 90° (32.7 vs. 51.8%) of knee flexion (all,  p  > 0.05). Similarly, for the biceps femoris, there were no differences between braced and unbraced conditions at 0° (22.5 vs. 23.2%), 30° (44.5 vs. 28.7%), 60° (47.2 vs. 44.6%), and 90° (32.7 vs. 51.8%) of knee flexion (all,  p  > 0.05). Finally, there were no differences between braced at 90° of knee flexion and unbraced at 0° of knee flexion with regard to semitendinosus (32.7 vs. 23.2%) and biceps femoris (32.6 vs. 23.2%) activity ( p  > 0.05).  Conclusions:  The use of a brace to limit knee extension did not decrease activation of the hamstrings during crutch-assisted ambulation in healthy participants. More research is needed to determine if the use of a knee brace is necessary following surgical repair of the hamstring tendon.