Short-term effect of unicompartmental knee arthroplasty on muscle coordination in patients with knee osteoarthritis.

BACKGROUDS

Over 60 % of knee osteoarthritis patients report experiencing the "giving way" phenomenon. This study aims to investigate the alterations in coordinated muscle contraction around the knee joint when the knee joint suddenly buckles under force, similar to "giving way", in the patients before and after unicompartmental knee arthroplasty.

METHODS

Twenty-five patients and 20 healthy adults were recruited to test the difference of muscle coordination between the patients before and about three months after surgery and healthy individuals. The self-designed force application equipment and a wireless surface electromyography system were used to collect the data on muscles activation when the legs were hit. The standard of significant difference was set as P < 0.05.

FINDINGS

There were significant differences between the test and control groups in the directed co-contraction ratios of the hamstring/quadriceps(P = 0.016) and the co-contraction index of the quadriceps-hamstring(P < 0.001) on the affected side, as well as in the directed co-contraction ratios of the biceps femoris/vastus lateralis(P = 0.020) on the unaffected side. Compared with data before the surgery, in directed co-contraction ratios and co-contraction index there was only a significant difference in directed co-contraction ratios of vastus lateralis/vastus medialis on the affected side(P < 0.001) but there were significant differences in the co-contraction index of quadriceps-hamstring(P = 0.004) and vastus medialis-semitendinosus(P = 0.001) on the unaffected side after the surgery.

INTERPRETATION

knee osteoarthritis affected the pattern of muscle co-contraction. In the short-term after the surgery, the co-contraction level in the affected side of patients did not have an obvious recovery but the activation level was improved, approaching healthy individuals.