Pelvic and Lower-Limb Intersegmental Kinematic Correlations During Two Single-Leg Landing Tasks One Year After Anterior Cruciate Ligament Reconstruction: An Exploratory Study

Background/Objectives: Intersegmental kinematic relationships after anterior cruciate ligament reconstruction (ACLR) remain poorly understood. This exploratory study examined pelvic, hip, knee, and ankle kinematic associations during two single-leg landing tasks in the operated (OP) and non-operated (NOP) limbs of individuals after ACLR and in the dominant limb of healthy controls (HLT). Methods: Sixteen individuals (13 males, 3 females) were assessed at a mean of 13 months after ACLR, together with 16 healthy controls. The landing phase of two single-leg tasks, the single-leg horizontal leap landing (SHLL) and the single-leg vertical drop landing (SVDL), was evaluated using a three-dimensional optoelectronic motion analysis system. Associations between pelvic, hip, knee, and ankle angles were assessed using Spearman’s correlation, with nominal (p < 0.05) and Bonferroni-corrected (p < 0.00091) thresholds. Results: After Bonferroni correction, significant correlations during SHLL were found between pelvic elevation and pelvic rotation (r = 0.79), pelvic elevation and hip adduction (r = 0.78), and pelvic rotation and hip adduction (r = 0.82) in OP; hip and knee flexion (r = 0.80) and knee flexion and adduction (r = −0.78) in NOP; and anterior pelvic tilt and hip flexion (r = 0.89), pelvic elevation and hip adduction (r = 0.81), and knee flexion and ankle dorsiflexion (r = 0.94) in HLT. During SVDL, anterior pelvic tilt correlated with hip flexion (NOP: r = 0.81; HLT: r = 0.88) and pelvic elevation with hip adduction (NOP: r = 0.92; HLT: r = 0.78), with none significant in OP. Conclusions: Pelvic and lower-limb kinematics were associated during both landing tasks in individuals approximately one year after ACLR and in healthy controls. These exploratory findings should be regarded as hypothesis-generating.