Medially Wedged Insoles Reduce Knee Pain During Functional Activities in Subjects with Lateral Knee Osteoarthritis

Abstract

We have previously demonstrated that laterally wedged orthotics can alleviate knee pain in subjects with medial compartment knee osteoarthritis. However, this effect has not yet been demonstrated in subjects with lateral knee osteoarthritis (LKOA) using a medially wedged orthotic. PURPOSE: To determine the effect of medially wedged orthotics on knee pain and function in subjects with LKOA. METHODS: As part of a larger study, ten subjects aged 65± 7 years with LKOA (K-L grades II-IV) were chosen for evaluation. Subjects were given an orthotic with an individually determined amount of wedging (range 5–15 degrees, average 9 ± 3 degrees) based on maximum pain reduction during a lateral step-down test. Subjects returned for testing following two weeks of accommodation to the orthotic. Two functional tests were performed: a walking test to see how far the subject could walk in six minutes, followed by a stair test to determine how long the subject took to ascend and descend a twelve step flight of stairs. No wedge (NW) and wedge (W) conditions were tested in random order. Subjects were asked to rate their knee pain before and after each test on a 100mm visual analog scale, 0 being no pain and 100 being the worst pain imaginable. Dependent t-tests (p≤0.05) were used to assess changes in walking distance, stair test time, and knee pain between the NW and W conditions. RESULTS: There were no differences between the NW and W conditions for six minute walk distance (p=0.57) or stair test time (p=0.12). For the stair test, knee pain significantly increased in the NW condition (pre-test pain 14.9±18.7mm, post-test pain 22.6±21.3mm; p=0.02) while there was no change in pain for the W condition (pre pain 11±12.3mm, post pain 13.8±15.5mm; p=0.16). Similar results were found for the six minute walk, with pain increasing significantly in the NW condition (pre pain 13.4±15.5mm, post pain 22.9±17.8mm; p=0.005) but not in the W condition (pre pain 11±15.6mm, post pain 17±18.7mm; p=0.25). CONCLUSION: Short term accommodation to medially wedged orthotics, while not affecting objective measures of functional ability, appear to prevent increases in knee pain associated with walking and stair climbing in patients with lateral knee OA. Support from NIH-RR16548 (Thomas Buchanan, PI) is acknowledged.