Efficacy of Lateral Wedge Orthotics during Level Walking in Patients with Medial Knee Osteoarthritis

Abstract

PURPOSE: Lateral wedge orthotics are designed to reduce medial tibiofemoral joint loading and pain in patients with knee osteoarthritis (OA). This study tested whether a lateral wedge orthotics treatment intervention for knee OA patients could significantly reduce medial knee joint loading and pain, and improve function over a 12-week period. METHODS: 36 women and men with medial compartment knee OA were randomly assigned to either the Orthotics group (7° lateral wedges) (n=18; mean age=60.8 ± 9.8 yrs; BMI=28.1 ± 3.7) or Control group (placebo neutral inserts) (n=18; mean age=61.0 ± 9.2 yrs; BMI=28.0 ± 4.3). Pain and functional levels were assessed with the WOMAC Osteoarthritis Index™, and a 100-mm visual analog scale (VAS). Three-dimensional kinematic and kinetic data during level walking were collected using a nine-camera motion analysis system and two force plates. Data were collected at Week 1, Week 6 and Week 12. Knee joint moments and angles were calculated using standard inverse dynamic techniques. Eleven dependent variables were analyzed with univariate Group (2) x Time (3) between/within ANOVA with a Bonferroni adjustment to protect against Type I error. RESULTS: The peak knee adduction moment (KAM) decreased 14.6% in the Orthotics group from Week 1 to Week 12 (p<0.05). However, the Control group, wearing neutral 52-durometer ethyl vinyl acetate “placebo” orthotics covered with 2-mm PVC foam to match the appearance of the lateral wedge orthotics, had a 5.3% decrease in peak KAM between Week 1 and Week 12 (p = 0.89). WOMAC™ activities of daily living subscores improved in both the Orthotics (44%) and Control groups (24%) (p < 0.05). Subjects in the Orthotics group reported an average of 58% reduction in their VAS pain scores during the walking trials from Week 1 to Week 12 (p < 0.05). CONCLUSION: Our findings suggest that 7° lateral wedge orthotics effectively lowered medial knee joint loading during level walking while significantly reducing pain and improving function over a 12-week period. While these findings are very promising, longitudinal studies are necessary to quantify the extent to which long-term use of lateral heel wedge orthotics slows the progression of medial knee OA. This research was Supported by an ACSM Foundation Research Grant (FRG) from the American College of Sports Medicine Foundation