The relationships among knee and patella alignments, body mass index, quadriceps, and knee adduction moments in healthy young females

Objective

To determine the relationships among knee and patella alignments, BMI, quadriceps, and knee adduction moments, which are associated with knee osteoarthritis, in healthy people.

Methods

In 60 young females, intercondylar distances normalized by body height, Q-angle, and BMI were assessed. The ratios of individual muscle:quadriceps thicknesses measured using ultrasonography were calculated. Correlations between these parameters were evaluated. Ten subjects were selected from the VALGUS, mild VARUS, or severe VARUS knee groups (<1.5 %, 1.5 %≤normalized intercondylar distance<2.0 %, and 2.0 %≤, respectively). The external knee adduction moments measured by three-dimensional gait analysis were compared among the 3 groups, and the correlations with BMI, the Q-angle, and the individual quadriceps thickness ratios were evaluated for each of the 3 groups.

Results

The normalized intercondylar distance and Q-angle increased as the vastus medialis:quadriceps thickness ratio increased (r = 0.29 and r = 0.28, respectively), while BMI increased as the vastus medialis:quadriceps thickness ratio decreased (rs = −0.59) and the rectus femoris:quadriceps thickness ratio increased (rs = 0.34). The knee adduction moment in the severe VARUS was greatest (effect size = 2.1 versus the VALGUS; effect size = 1.7 versus the mild VARUS); however, the knee adduction moment increased as the vastus medialis:quadriceps thickness ratio decreased (r = −0.68) and the rectus femoris:quadriceps thickness ratio increased (r = 0.66) in the mild VARUS, whereas the knee adduction moment increased as the Q-angle decreased in the severe VARUS (rs = −0.83).

Conclusion

The vastus medialis:quadriceps thickness ratio was related to knee and patellar alignment and BMI. The mechanism by which the knee adduction moment is reduced differs according to the degree of knee alignment.