Landing kinematics and kinetics at the knee during different landing tasks

Context: Several tasks have been used to examine landing biomechanics for evaluation and rehabilitation, especially as related to anterior cruciate ligament injuries. However, comparing results among studies in which different tasks were used can be difficult, and it is unclear which task may be most appropriate. Objective: To compare lower extremity biomechanics across 5 commonly used landing tasks. Design: Descriptive laboratory study. Setting: University-operated US Air Force Special Operations Forces human performance research laboratory. Patients or Other Participants: A total of 65 US Air Force Special Tactics Operators (age = 27.7 ± 5.0 years, height = 176.5 ± 5.7 cm, mass = 83.1 ± 9.1 kg). Intervention(s): Kinematic and kinetic analysis of doubleand single-legged drop landing, double- and single-legged stop jump, and forward jump to single-legged landing. Main Outcome Measure(s): Hip-, knee-, and ankle-joint kinematics; knee-joint forces and moments; and ground reaction forces (GRFs) were the dependent measures. We used repeated-measures analyses of variance or Friedman tests, as appropriate, to assess within-subject differences across tasks. Results: Peak vertical GRF and peak knee-flexion angle were different among all tasks (P> 001). Single-legged landings generated higher vertical GRF (v2 = 244.68, P> .001) and lower peak knee-flexion values (F4,64 = 209.33, P> .001) except for forward jump to single-legged landing, which had the second highest peak vertical GRF and the lowest peak knee-flexion value. The single-legged drop landing generated the highest vertical (v2 = 244.68, P> .001) and posterior (v2 = 164.46, P> .001) GRFs. Peak knee-valgus moment was higher during the double-legged drop landing (v2 = 239.63, P> .001) but similar for all others. Conclusions: Different landing tasks elicited different biomechanical responses; no single task was best for assessing a wide range of biomechanical variables related to anterior cruciate ligament injuries. Therefore, depending on the goals of the study, using multiple assessment tasks should be considered.