Time-Dependent Alterations in Walking Biomechanics After Anterior Cruciate Ligament Reconstruction Compared with Healthy Individuals: A Systematic Review with Meta-analysis.

BACKGROUND

Knee injuries involving the anterior cruciate ligament (ACL) are often treated through surgical care to restore knee joint stability. Despite surgical treatment, there is evidence of altered biomechanical gait characteristics for short-, mid-, and even long-term post ACL reconstruction (ACLR).

OBJECTIVE

In this systematic review with meta-analysis, we aimed to analyze lower extremity joint kinematics and kinetics recorded during walking in individuals with ACLR and determine the time course of recovery of gait biomechanics following ACLR.

METHODS

Five electronic databases (Scopus, PubMed, EMBASE, Physiotherapy Evidence Database (PEDro), Cochrane Central Register of Controlled Trials [CENTRAL]) were systematically searched for articles potentially eligible for inclusion from inception until January 2026. A PECOS (

Participants

ACLR individuals aged ≥ 18; Exposure: ACL surgery; Comparators: healthy controls; Outcomes: lower limb kinematics and kinetics during the walking stance phase; and Study design: case control studies, case series, cross-sectional studies, randomized controlled trials [baseline], cohort studies) approach was applied to define inclusion and exclusion criteria. Using cross-sectional studies, gait biomechanics were assessed short- (0-<6 months), mid- (≥ 6-12 months), and long-term (≥ 12 months) post-surgery in ACLR patients versus healthy controls. Gait biomechanics assessed during the stance phase were extracted from the included articles. Between-group standardized mean differences (SMD) with 95% confidence intervals (CI) were computed using a random-effects model to elucidate the gait biomechanical differences between ACLR patients and healthy controls. The modified version of the Downs and Black checklist was used to assess the methodological quality of the included studies.

RESULTS

The initial search identified 3199 hits and according to a priori defined in-/exclusion criteria, 31 cross-sectional studies with males and females aged 17-55 years were eligible to be included. The mean methodological quality of all included studies was moderate (Downs and Black checklist score: 68%). Based on outcomes from 17 studies, lower peak knee flexion angles were noted during the stance phase of walking in ACLR patients compared to controls (small SMD=-0.50, 95% CI -0.77 to -0.22, p = 0.0004, I2 = 79%) which could even be found ≥ 12 months post-surgery (11 studies: small SMD=-0.49, 95% CI -0.84 to -0.15, p = 0.005, I2 = 83%). Up until six months post-surgery, lower peak knee adduction angles (four studies: moderate SMD=-0.56, 95% CI -0.96 to -0.16, p = 0.006, I2 = 47%) were observed in ACLR patients. Regarding kinetics, irrespective of the time point post ACLR, the peak knee flexor joint moments (11 studies: moderate SMD=-0.57, 95% CI -0.90 to -0.25, p = 0.0005, I2 = 69%) were lower in the ACLR group compared to controls.

CONCLUSIONS

After ACLR, the observed reduction in peak knee flexion angle suggests a walking pattern with a straighter knee, or a less erect gait posture, which can persist for ≥ 12 months post surgery. The lower sagittal plane knee moments suggest a less dynamic gait, characterized by reduced muscular demand. The small deviations in gait biomechanics from normal are lasting but inconsistent between studies. While associated with long-term outcomes like post-traumatic osteoarthritis, the direct clinical relevance of these specific gait changes requires further study.