Lower limb kinematic changes during stair navigation 3 and 5 months after anterior cruciate ligament reconstruction: A longitudinal analysis in real-world settings

Background: Despite advancements in anterior cruciate ligament reconstruction (ACLR), achieving symmetrical movement patterns during stair negotiation remains challenging. Therefore, this study examines lower limb kinematics during stair ambulation at the early and mid-rehabilitation stages after ACLR in a real-world environment. Objective: To describe lower limb kinematics during stair ambulation at 3 and 5 months after ACLR and evaluate changes between these time points. We hypothesized that between-limb asymmetries would improve over this period. Design: Longitudinal study. Participants: Twenty-seven patients 3 months post ACLR were recruited, and 18 were followed up at 5 months post ACLR. Surgeries were performed by one of five surgeons using various grafts (hamstrings, bone-patellar tendon-bone, or quadriceps). Exclusion criteria were multiligament injuries, major meniscus injuries, other concomitant injuries, or previous knee surgeries. An additional group of matched healthy controls (n = 16) was also recruited. Setting: Public health care campus. Interventions: N/A. Main Outcome Measures: Maximum and minimum joint angles, and continuous kinematic patterns during stair ascent and descent were measured on a 20-step staircase at self-selected speed using seven inertial measurement units, with sagittal knee kinematics as the main outcome and hip and ankle kinematics as secondary outcomes. Between-limb differences and longitudinal changes were analyzed using discrete points and statistical parametric mapping. Results: At 3 months after ACLR, the injured knee was less flexed compared to the contralateral knee during stair ascent (mean difference = −11.3°, confidence interval [CI, −14.4 to −8.1], p <.001) and descent (mean difference = −6.3°, CI [−10.2 to −2.4], p =.002). Statistical parametric mapping analysis showed decreased flexion at 0%–35% and 87%–99% of the stair ascent cycle (p <.005). By 5 months, flexion differences during ascent improved (mean difference = −4.7°, CI [−8.1 to −1.4], p =.008), but asymmetry persisted, with decreased flexion at 10%–32% of the cycle during ascent and 20%–29% during descent (p <.017). Flexion improvements were observed from 3 to 5 months during ascent (mean increase = 6.1°, p <.001) and descent (mean increase = 9.3°, p =.004). Conclusions: Persistent lower limb kinematic asymmetries remain 5 months after ACLR during stair ambulation.