Patients with knee osteoarthritis often have weakness of their hip abductor muscles. Knee osteoarthritis patients have also been shown to have altered biomechancis at the hip, leading to abnormal loading on the medial side of their knee joint. This increase in loading is thought to result in an increased knee adductor moment during gait because of weak hip abductors. Several studies have shown that Thera-Band elastic resistance exercise can decrease pain and increase function in patients with knee osteoarthritis.
Researchers in Canada wanted to see if an 8-week home strengthening program could improve joint loading, strength, pain and function in patients with medial knee osteoarthritis. 40 patients, along with 40 age-matched control subjects without arthritis were included in the study. The patients with knee osteoarthritis had 25% weaker hip abductor strength and significantly greater hip adductor moments compared to the control group.
The home exercise program included sidelying and standing hip abduction strengthening, progressing to elastic bands. The group with knee arthritis performed exercises 3 to 4 times a week with one set to fatigue on both legs. When they could complete 20 repetitions without fatigue, they progressed to the next color band.
After 8 weeks, the osteoarthritis group significantly increased their hip abduction strength to reach the level equal to the non-arthritis group. In addition, the patients significantly improved their functional performance and reduced their knee pain. Interestingly, however, while the patients improved their strength, pain and function, their knee adduction moment remained the same.
The authors concluded that hip strengthening exercises in patients with knee osteoarthritis can increase hip strength and function, but do not improve joint knee joint loading.
It’s important to note that hip abduction strength was measured in an open kinetic chain with an isokinetic dynamometer, which may not be indicative of the functional strength of the hip abductors in a closed chain. It’s possible that the function of the hip abductors in a closed chain may have a different influence on the hip adductor moment compared to the open chain.
While the elastic-resisted exercises were performed in both an open and closed kinetic chain, it’s possible that a different exercise may be necessary to improve the hip adductor moment. Nonetheless, the results of this study agree with other studies showing that Thera-Band exercise bands can be used effectively to reduce pain and increase strength and function in knee osteoarthritis patients.
REFERENCE: Sled EA, Khoja L, Deluzio KJ, Olney SJ, Culham EG. Effect of a home program of hip abductor exercises on knee joint loading, strength, function, and pain in people with knee osteoarthritis: a clinical trial. Phys Ther. 2010 Jun;90(6):895-904. Epub 2010 Apr 8.