The biomechanical effects of focused muscle training on medial knee loads in OA of the knee: a pilot, proof of concept study.

BACKGROUND: High dynamic loads of the medial knee are associated with tibiofemoral osteoarthritis (OA) severity and progression. The lower extremity acts as an integrated kinetic unit, thus treatments targeting adjacent segments may promote reductions in the loading of a symptomatic knee. This study examined the biomechanical effects of a lower extremity exercise regimen, emphasizing training of hip abductor musculature, on dynamic knee loads in individuals with knee OA. METHODS: Six subjects with medial compartment knee OA participated in a proof of concept study of a four-week exercise program specifically targeting the hip abductor musculature in combination with traditional quadriceps and hamstring training. Assessments included gait analyses to measure the external knee adduction moment, a surrogate marker of medial knee joint loading as well as WOMAC questionnaires and strength evaluations. RESULTS: All subjects demonstrated a decrease in their external knee adduction moment, with an average decrease of 9% (p<0.05) following the exercise intervention. There was a 78% (p<0.05) decrease in WOMAC knee pain scores. CONCLUSIONS: These results suggest that targeting hip, rather than only knee musculature, may represent an effective biomechanically-based treatment option for medial knee OA.

Bone mineral density in the proximal tibia varies as a function of static alignment and knee adduction angular momentum in individuals with medial knee osteoarthritis.

Based on the premise that bone mass and bone geometry are related to load history and that subchondral bone may play a role in osteoarthritis (OA), we sought to determine if static and dynamic markers of knee joint loads explain variance in the medial-to-lateral ratio of proximal tibial bone mineral density (BMD) in subjects with mild and moderate medial knee OA. We utilized two surrogate markers of dynamic load, the peak knee adduction moment and the knee adduction angular momentum, the latter being the time integral of the frontal plane knee joint moment. BMD for medial and lateral regions of the proximal tibial plateau and one distal region in the tibial shaft was measured in 84 symptomatic subjects with Kellgren and Lawrence radiographic OA grades of 2 or 3. Utilizing gait analysis, the peak knee adduction moment (the external adduction moment of greatest magnitude) and the time integral of the frontal plane knee joint moment (the angular momentum) over the entire stance phase as well as for each of the four subdivisions of stance were calculated. The BMD ratio was not significantly different in grade 2 (1.32 +/- 0.27) and grade 3 knees (1.47 +/- 0.40) (P = 0.215). BMD of the tibial shaft was not correlated with any loading parameter or static alignment. Of all the surrogate gait markers of dynamic load, the knee adduction angular momentum in terminal stance explained the most variance (20%) in the medial-to-lateral BMD ratio (adjusted r(2) = 0.196, P < 0.001). The knee adduction angular momentum for the entire stance phase explained 18% of the variance in the BMD ratio (adjusted r(2) = 0.178, P < 0.001), 10% more variance than explained by the overall peak knee adduction moment (adjusted r(2) = 0.081, P < 0.001). 18% of the variance in the BMD ratio was also explained by the knee alignment angle (adjusted r(2) = 0.183, P < 0.001), and the total explanatory power was increased to 22% when the knee adduction angular momentum in terminal stance was added (change in r(2) = 0.041, P < 0.05, total adjusted r(2) = 0.215, P < 0.001). The BMD ratio and its relationship to dynamic and static markers of loading were independent of height, weight, and the body mass index, demonstrating that both dynamic markers of knee loading as well as knee alignment explained variance in the tibial BMD ratio independent of body size.