Dynamic valgus alignment and functional strength in males and females during maturation.

CONTEXT Sex differences in dynamic measures have been established in physically mature populations. Gaining information on maturation's effect on dynamic performance measures implicated in injury risk may enable us to better design injury prevention programs. OBJECTIVE To examine sex differences in dynamic valgus alignment and triple-hop distance measures across maturational stages in males and females. A secondary purpose was to determine if a field test of strength and power predicts dynamic valgus alignment. DESIGN Cross-sectional study. SETTING Laboratory. PATIENTS OR OTHER PARTICIPANTS 157 young athletes (78 females, 79 males) aged 9 to 18 years. INTERVENTION(S) Subjects performed drop-jump landings and single-leg triple-hop tests as part of a broader injury screening. MAIN OUTCOME MEASURE(S) Maturational status was ascertained from self-report questionnaires and grouped according to Tanner stages 1 and 2 (MatGrp1), 3 and 4 (MatGrp2), and 5 (MatGrp3). Frontal-plane knee valgus displacement, which served as a measure of dynamic valgus alignment, and single-leg triple-hop distance were assessed. RESULTS Males demonstrated less dynamic valgus alignment during drop jumps in the latter maturational stages (MatGrp1 = 13.1 degrees +/- 8.7 degrees , MatGrp2 = 9.0 degrees +/- 6.2 degrees , MatGrp3 = 9.2 degrees +/- 9.4 degrees ), whereas females increased dynamic valgus alignment throughout maturation (MatGrp1 = 11.5 degrees +/- 6.9 degrees , MatGrp2 = 12.8 degrees +/- 8.8 degrees , MatGrp3 = 15.5 degrees +/- 8.7 degrees ). Thus, in the more mature groups, males had less dynamic valgus alignment than females. Both males (MatGrp1 = 393.5 +/- 63.7 cm, MatGrp2 = 491.8 +/- 95.1 cm, MatGrp3 = 559.3 +/- 76.3 cm) and females (MatGrp1 = 360.3 +/- 37.1 cm, MatGrp2 = 380.1 +/- 44.3 cm, MatGrp3 = 440.0 +/- 66.2 cm) increased triple-hop distance, but males increased more. Within each subgroup of MatGrp and sex, triple-hop distance had no predictive ability for dynamic malalignment. CONCLUSIONS When dynamic valgus alignment and strength were assessed, sex and maturational status displayed an interaction. However, functional strength did not predict degree of dynamic valgus alignment.