Neuromuscular risk factors for non-contact knee injury: a systematic review and meta-analysis

ABSTRACT Objectives Identify neuromuscular risk factors for non-contact knee injury, using a systematic review and meta-analysis, to inform the development of preventive strategies. Methods Medline, Web of Science and SCOPUS were searched from inception until November 2020. Prospective and nested case-control studies that analysed baseline neuromuscular characteristics as potential risk factors for subsequent non-contact knee injuries were included. Two reviewers independently appraised methodological quality using a modified Newcastle–Ottawa Scale. Meta-analysis was performed where appropriate, with standardised mean differences calculated for continuous scaled data. Results Seventeen studies were included, comprising baseline data from 5,584 participants and 415 non-contact knee injuries (heterogeneous incidence = 7.4%). Protocols and outcome measures differed across studies, limiting data pooling. Twenty-one neuromuscular variables were included in the meta-analysis. Three were identified as risk factors. For patellofemoral pain, among military recruits: reduced non-normalised quadriceps strength at 60º/s (SMD −0.66; 95% CI −0.99, −0.32); reduced quadriceps strength at 240º/s (normalised by body mass) (SMD −0.53; CI −0.87, −0.20). For PFP/ACL injury among female military recruits: reduced quadriceps strength at 60º/s (normalised by body mass) (SMD −0.50; CI −0.92, −0.08). Conclusions Quadriceps weakness is a risk factor for PFP among military recruits, and for PFP/ACL injury among female military recruits. However, the effect sizes are small, and the generalisability of these findings is limited. The effectiveness of quadriceps strengthening interventions for preventing PFP and ACL injury merits evaluation in prospective randomised trials.