Change in KOOS and WOMAC Scores in a Young Athletic Population With and Without Anterior Cruciate Ligament Injury

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Several studies have examined changes in patient-reported outcome measures (PROMs) after anterior cruciate ligament (ACL) injury, but no studies to date have prospectively evaluated changes from preinjury baseline through injury and follow-up among ACL-injured patients compared to the baseline and follow-up changes of uninjured patients.


To examine changes in PROMs over time from preinjury baseline to at least 2 years after ACL reconstruction and to compare these changes with those of an uninjured control group having similar physical activity requirements.

Study Design:

Cohort study; Level of evidence, 2.


The authors conducted a prospective cohort study with a nested case-control analysis at a US service academy. All incoming first year students were recruited to participate in this study. Consenting participants completed a baseline questionnaire that included the KOOS (Knee injury and Osteoarthritis Outcome Score), WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), and MARS (Marx Activity Rating Scale). Participants who sustained a subsequent ACL injury completed assessments at the time of surgery and at 6, 12, and 24 months after surgery. Healthy participants were recruited to repeat the baseline assessments within 1 year of graduation. Inter- and intragroup differences at these time points were evaluated with dependent and independent t tests, respectively. We also compared these results with established minimum clinically important difference (MCID) values.


Of 1268 first year students entering the academy, 1005 with no previous injuries consented to participate in this study (82% male, mean ± SD age 19 ± 1 years). Of those enrolled, 30 suffered an ACL injury and met the inclusion criteria for this study. Ninety uninjured control students who met the inclusion criteria completed follow-up assessments. There were statistically significant differences across all KOOS and WOMAC subscales between ACL-injured group and uninjured group at the time of the final follow-up assessment. Four KOOS subscales (Pain, Symptoms, Sports and Recreation Function, and Knee-Related Quality of Life) and the WOMAC Stiffness subscale demonstrated >8-point differences between groups, which exceeded the established MCID for these instruments. There were no significant differences between the ACL-injured group and uninjured groups noted for the MARS (P = .635). At the time of final follow-up, the ACL-injured group also reported significant deficits on the WOMAC Stiffness subscale (P = .032), the MARS (P = .030), and all KOOS subscales, with the exception of Functional Activities of Daily Living, as compared with their preinjury baseline scores. These deficits exceeded the established MCID values for 3 KOOS subscales and the MARS.


Patients with ACL injuries reported significant deficits on PROMs at least 2 years after surgical reconstruction in relation to preinjury baseline scores and an uninjured control group. Many of these deficits exceeded established MCID values.

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