Drop-Landing Performance and Knee-Extension Strength After Anterior Cruciate Ligament Reconstruction

Context Individuals with a history of anterior cruciate ligament reconstruction (ACLR) are at greater risk of reinjury and developing early-onset osteoarthritis due to persistent abnormal joint loading. Real-time clinical assessment tools may help identify patients experiencing abnormal movement patterns after ACLR. Objective To compare performance on the Landing Error Scoring System (LESS) between participants with ACLR and uninjured control participants and to determine the relationship between LESS score and knee-extension strength in these participants. Design Controlled laboratory study. Setting Research laboratory. Patients or Other Participants Forty-six recreationally active participants, consisting of 22 with ACLR (12 men, 10 women; age = 22.5 ± 5.0 years, height = 172.8 ± 7.2 cm, mass = 74.2 ± 15.6 kg, body mass index = 24.6 ± 4.0) and 24 healthy control participants (12 men, 12 women; age = 21.7 ± 3.6 years, height = 168.0 ± 8.8 cm, mass = 69.2 ± 13.6 kg, body mass index = 24.3 ± 3.2) were enrolled. Main Outcome Measure(s) Bilateral normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg) and LESS scores were measured during a single testing session. We compared LESS scores between groups using a Mann-Whitney U test and the relationships between LESS scores and normalized knee-extension MVIC torque using Spearman ρ bivariate correlations. Results The ACLR participants had a greater number of LESS errors (6.0 ± 3.6) than healthy control participants (2.8 ± 2.2; t44 = −3.73, P = .002). In ACLR participants, lower normalized knee-extension MVIC torque in the injured limb (ρ = −0.455, P = .03) was associated with a greater number of landing errors. Conclusions Participants with ACLR displayed more errors while landing. The occurrence of landing errors was negatively correlated with knee-extension strength, suggesting that weaker participants had more landing errors. Persistent quadriceps weakness commonly associated with ACLR may be related to a reduced quality of lower extremity movement during dynamic tasks.