Background/aim Consequences of an anterior cruciate ligament (ACL) injury include worse patient-reported outcomes (PROs) and a decrease in activity level. Muscle function can be improved by targeted exercise. Our aims were to investigate cross-sectional and longitudinal associations among lower extremity muscle function and PROs after ACL injury.
Methods Fifty-four participants (15 women, mean 30 years) with ACL injury or reconstruction, from the Knee Anterior Cruciate Ligament, Nonsurgical versus Surgical Treatment (KANON) trial (ISRCTN84752559), were assessed with hop performance, muscle power and postural orientation 3 years (SD 0.85) after ACL injury. PROs at 3 and 5 years after injury included Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales Function in sport and recreation (KOOS Sport/rec) and Knee-related Quality of life (KOOS QoL), KOOS item Q3 (KOOS Q3), Tegner Activity Scale and Activity Rating Scale (ARS). Partial Spearman's rank-order correlation was used to analyse correlations between muscle function and PROs, controlling for gender and treatment.
Results Numerous cross-sectional correlations were observed between muscle function and PROs (rsp≈0.3–0.5, p≤0.045). Worse hop performance and worse postural orientation were associated with worse KOOS scores 2 years later (rsp≥0.280, p≤0.045). Worse muscle power was associated with lower future ARS scores (rsp=0.281, p=0.044).
Conclusions The moderate associations suggest that improving muscle function during rehabilitation could improve present and future PROs.
- Knee injuries
- Exercise rehabilitation
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Contributors All authors contributed to the study design. EA and EMR collected the data. VF was responsible for the analysis and interpretation of the data, and wrote the first draft of the manuscript. EA contributed in analysis and interpretation of data, contributed in writing the manuscript and provided feedback on drafts of this paper. EMR contributed in interpretation of data and critically revised the manuscript for important intellectual content. All authors approved the final manuscript.
Funding This research was funded by the Swedish Research Council (2009-1447), the Crafoord Foundation, the Swedish Rheumatism Association, the Swedish National Centre for Research in Sports and the Faculty of Medicine of Lund University. The original KANON study, from which the patients were included, was additionally supported by Pfizer Global Research, Thelma Zoegas Fund, the Swedish National Centre for Research in Sports and the Stig & Ragna Gorthon Research Fund.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Research Ethics Committee at Lund University.
Provenance and peer review Not commissioned; externally peer reviewed.