Background: Altered lower limb movement patterns (LLMP) during the forward step down (FSD) test have been studied in people suffering from knee instability. However, ankle dorsiflexion range of motion (ADROM) seems to be related to LLMP but no causal inference has been defined between those variables.
Objective: Our goals were to evaluate (1) psychometric quality of the FSD test in healthy people and (2) the influence of experimental restricted ADROM on LLMP.
Methods: Kinematics were measured by a motion capture system. Angular displacement and speed were calculated as well as center of mass (COM) and knee linear displacement. Forty-two healthy participants; firstly, performed the test three times to assess reliability, and secondly the same test in an experimental condition limiting the ADROM.
Results: Reliability was excellent for all parameters (ICC: 0.75-0.99, SEM%: 2.0-34.0%). ADROM limitation significantly decreased Knee flexion range of motion (ROM) (-3.8∘), increased Hip flexion ROM (6∘), Hip adduction ROM (6.1∘), Pelvis drop ROM (3.5∘), Pelvic rotation ROM (3.1∘). No significant effect was found for Hip rotation ROM.
Conclusions: LLMP was affected by this experimental ADROM limitation in healthy people. As this limitation is often encountered in post-traumatic ankle sprain patients, clinicians should consider this point during FSD assessment test.
Keywords: Lower limb; biomechanics; functional tests; kinematics; movement pattern.