Noncontact knee injuries are a major problem for male and female agility sports athletes. These injuries commonly manifest with a valgus collapse that implicates failure of mechanical and/or sensorimotor mechanisms in maintaining knee functional joint stability (FJS). Previous studies have elucidated the role of some mechanical and sensorimotor characteristics in knee FJS. The contributions of active joint position sense (AJPS) and time-to-peak torque (TTPT) have not been investigated. Therefore, the current evidence-base is incomplete and noncontact knee injury control programs may not be as effective as could be. Identifying the role of AJPS and TTPT in knee FJS will deliver new data that potentially assists design of more effective noncontact knee injury control programs. The purpose of this study was to determine how gender, mechanical joint stability, and selected sensorimotor characteristics predict knee FJS. Two analyses were performed, each with a specific operational definition of knee FJS: 1. adapted crossover hop for distance (ACHD); 2. single-leg stop-jump (SLSJ) total knee valgus displacement.
Thirty-four subjects participated (male (M) 18; female (F) 16; age 24.1 ± 3.5 years; height 171.8 ± 9.6cm; mass 70.6 ± 12.2kg). The dominant leg was tested. The ACHD analysis included: ACHD (cm), gender (M/F), prone knee extension AJPS (motion analysis system; °), anterior tibial displacement (ATD; mm), and isokinetic hamstrings TTPT (240°•sec–1; msec). The SLSJ analysis included: SLSJ valgus/varus displacement (motion analysis system; °), gender, AJPS, ATD, SLSJ medial hamstrings feedforward and feedback muscle activation (surface electromyography; % maximum voluntary isometric contraction × sec), and TTPT. Multiple linear regression was performed.
For the ACHD analysis, gender and TTPT contributed to a model that predicted ACHD performance (R2 = 0.60, P = 0.00). For the SLSJ analysis, 56% of subjects demonstrated varus displacement and valgus/varus raw data and final equation residuals demonstrated a non-normal distribution.
Gender and hamstrings TTPT should be considered in noncontact knee injury control programs evaluated by single-leg hop tests. Future multivariate studies should consider new knee proprioception tests and employ additional functional tasks to identify clinically important knee valgus displacement
