Purpose: Impaired hip kinematics have been associated with high magnitude medial knee joint loads in patients with knee osteoarthritis (OA). Therefore, a brace designed to pull the femur into external rotation and augment hip muscle function might be able to lower the internal knee abduction moment during walking. Several studies have utilized the internal knee abduction moment as an estimate of medial knee joint loading. However, to our knowledge, no study has evaluated the effect bracing of the femur will have on tibiofemoral joint kinetics in patients with medial knee OA. The purpose of this study was to determine if a femoral external rotation strap will reduce medial knee joint loading and decrease pain during level walking in patients with medial knee OA. Methods: Fifteen women and men with medial knee compartment OA (mean age=60.8(plus or minus)9.8 yrs; BMI=28.1(plus or minus)3.7) ambulated over a 10 meter walkway during two conditions: (1) wearing the femoral external rotation strap (braced) and (2) without the strap (unbraced). Five trials were collected at the subject's self selected pace ((plus or minus)5%) for each randomly assigned condition. The brace used in this study was a thin elastic strap that wraps around the femur and the pelvis thus pulling the femur into external rotation. Threedimensional kinematic data were collected using an 8-camera infrared motion capture system (Motion Analysis Corp, Santa Rosa, CA) while two force plates collected ground reaction force data (AMTI, Boston, MA) during each walking trial. Pain during level walking was assessed with a 100-mm visual analog scale (VAS) during the braced and unbraced conditions. Peak knee and hip moments and angles were quantified during the stance phase of the normal gait cycle using Orthotrack software (Motion Analysis Corp, Santa Rosa, CA). Peak knee and hip moments and angles were averaged across five trials for the braced and unbraced conditions. Paired t-tests with Bonferroni adjustments were utilized for comparisons between the braced and unbraced conditions ((alpha)=0.05). Results: During the braced condition, hip external rotation angles significantly increased (6.0(plus or minus)5.3 (degrees), unbraced; 15.4(plus or minus)5.3(degrees), braced) and hip adduction angles significantly decreased (4.3(plus or minus)2.5(degrees), unbraced; 1.1(plus or minus)2.5(degrees), braced) (p<0.05). The strap also resulted in significantly reduced frontal plane pelvic angles (2.6(plus or minus)2(degrees), braced; 4.7(plus or minus)1.8(degrees), unbraced) (p<0.05). There was a 28% lower first peak internal knee abduction moment during the braced versus the unbraced condition (p<0.05). Sagittal plane hip and knee angles did not change significantly between conditions (p>0.05). Likewise, no significant differences were found in frontal or transverse plane knee angles (p>0.05). While walking with the hip strap, subject reported a 35% decrease in their reported pain levels. Conclusion: These data suggest that increasing femoral external rotation and decreasing adduction of the pelvis can result in a lower knee adduction moment in patients with medial knee OA. During the stance phase of gait, the femoral external rotation strap appears to control frontal plane pelvic motion thus possibly causing the changes in the internal knee abduction moment. As the contralateral iliac crest remains elevated, this could move the center mass closer to the knee joint axis thus resulting in a reduction in the knee joint moment. These findings support the strengthening of the hip muscles as a treatment for patients with medial knee osteoarthritis. Enhanced hip muscle strength could reduce pelvic motion and improve hip stability, thereby decreasing medial knee joint forces. Future studies will need to develop specific treatment regiments that target the appropriate hip muscles to produce long-term improvements for patients with medial knee OA.
Wallace, D. A., & Barr, C. (2010). 142 THE ROLE OF THE HIP ON KNEE JOINT MECHANICS DURING LEVEL WALKING IN PATIENTS WITH MEDIAL KNEE OSTEOARTHRITIS. Osteoarthritis and Cartilage, 18, S70–S71. https://doi.org/10.1016/s1063-4584(10)60169-0