Landing mechanics after anterior cruciate ligament reconstruction: reliability and clinical insights from the forward single-leg hop test

OBJECTIVES: To evaluate inter-rater reliability of the Single-leg Hop for Distance Landing Error Scoring System (SHD-LESS), compare landing mechanics between limbs, examine associations with strength and functional performance, and identify coordinated movement patterns following anterior cruciate ligament reconstruction (ACLR). DESIGN: Cross-sectional. SETTING: University hospital. PARTICIPANTS: Fifty-seven athletes (mean age 25.5 ± 6.2 years) assessed 6-12 months post-primary unilateral ACLR. MAIN OUTCOME MEASURES: Bilateral isokinetic strength (60°/s) and single-leg hop distance were assessed. Two blinded raters independently scored landing quality using the SHD-LESS (13 items, maximum score 16) from 120 fps video recordings. Inter-rater reliability was assessed using ICC and Cohen's κ, with limb comparisons via McNemar's and Wilcoxon signed-rank tests. RESULTS: SHD-LESS total score demonstrated good inter-rater reliability (ICC 0.77-0.80), with variable item-level agreement. The operated limb showed greater landing errors. Inter-item correlations revealed coordinated multi-joint kinematic deficits encompassing sagittal load absorption, frontal-plane dynamic valgus, and trunk-hip compensatory patterns. Higher pre-injury activity level and muscle strength were associated with lower SHD-LESS scores, while return-to-running status was the sole predictor of interlimb asymmetry. CONCLUSIONS: SHD-LESS is a reliable, clinically feasible tool revealing landing quality deficits beyond hop distance alone, relevant to return-to-sport decision-making after ACLR.