Loading Patterns During Landing Tasks in Active-Duty Special Operations Forces Personnel

Context The highest incidences of musculoskeletal injuries within the military occur at anatomic regions most affected by jumping and landing, including the knee. Military personnel assigned to Special Operations Forces (SOF) are at particularly high risk of musculoskeletal injury due to occupational demands. Objectives To identify loading patterns and landing strategies used by SOF personnel during different landing tasks and examine the relationships between knee strength, landing knee mechanics, and shock attenuation. Design Cross-sectional study. Setting Laboratory. Patients or Other Participants A total of 224 uninjured active-duty male SOF personnel (age = 27.7 ± 5.0 years, height = 176.5 ± 5.7 cm, mass = 83.1 ± 9.1 kg) completed biomechanical analyses of 2 different drop-landing tasks (double-legged drop landing [DLDL] and single-legged drop landing [SLDL]) and isokinetic strength testing of the quadriceps and hamstrings muscles. Main Outcome Measure(s) Peak hip, knee, and ankle angles; hip, knee, and ankle angles at initial ground contact; and peak vertical ground reaction forces (VGRFs) were identified during landing tasks. Maximal voluntary isokinetic knee-extension strength (KES) and knee-flexion strength were also assessed. Results Participants demonstrated greater KES with their dominant limb by a mean of 0.06 N·m/kg ( P = .001, Cohen d = 0.219) and landed with greater force on the dominant limb during the DLDL by a mean of 19.81% body weight ( P < .001, Cohen d = 0.377). No asymmetries involving knee kinematics were identified. During the DLDL, both limbs demonstrated similar correlations between knee (peak: r range, −0.405 to −0.342; P < .001) and ankle (initial ground contact: r range, 0.249 to 0.349; P ≤ .001 and peak: r range, −0.300 to −0.241; P ≤ .002) kinematics and peak VGRF. During the nondominant SLDL, the knee at initial ground contact, peak knee flexion, and peak dorsiflexion were correlated with peak VGRF ( r range, −0.404 to −0.332; P ≤ .002). Peak knee flexion during the nondominant SLDL was correlated with KES ( r = 0.262, P = .02). Conclusions Knee mechanics are important components for shock attenuation, but for this population, factors other than strength likely played a more important role in controlling the mechanics about the knee during landing tasks.