The influence of varus and valgus deviation on the contact area of patellofemoral joint in healthy knees.

objectVarus-valgus lower alignment is a risk factor for patellofemoral osteoarthritis, but malalignment alone affect not only the tibiofemoral joint but also the patellofemoral joint. The aim of the present study was to analyse the contact area of patellofemoral joint in varus alignment and valgus alignment of healthy subjects using magnetic resonance imaging.

methodsTwenty-six healthy subjects with valgus lower limb alignment (Group I, n = 26) and twenty-six volunteers with varus lower limb alignment (Group II, n = 26) was performed. An MRI scan was used to capture and measure the patellofemoral joint articular cartilage contact area at different degrees of knee flexion (20°, 40°,60°) in passive movement. All subjects were categorized on the basis of the global limb alignment and mechanical alignment of the femur and tibia. Varus alignment is hip-knee-ankle angle ≥ 3°; and valgus alignment is hip-knee-ankle angle ≥ - 3°. To obtain medial facet contact area and lateral facet contact area for each slice, the length of each respective line of contact was multiplied by the 5 mm slice thickness.

resultsThe overall joint contact area increased from 168.0 ± 20.5 mm

conclusionsThroughout the knee movement, the contact area on the lateral facet of the patellofemoral joint was greater in the valgus group. In the early phase of knee flexion, the contact area of the medial patellofemoral joint was larger in the varus group. Lower alignment is an important factor in patellofemoral joint degeneration.