Normative values for the KOOS and WOMAC in a young athletic population: history of knee ligament injury is associated with lower scores.

BACKGROUND

The use of patient-reported outcome measures to assess clinical outcomes after injury and surgery has become common in treating young athletes with orthopaedic injuries; however, normative data for these measures are limited and often include a wide range of ages and activity levels.

PURPOSE

To provide normative data for the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in a young and athletic population, and to compare scores between participants with a history of knee ligament injury and those with no history.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We administered the KOOS and WOMAC to 1177 college freshmen entering the United States Military Academy in June 2011. All participants were healthy and had been medically screened to meet the physical induction standards for military service. We calculated means, standard deviations, percentiles, ranges, and interquartile ranges for the KOOS and WOMAC by sex and injury history. We also compared median scale scores for those with a history of knee ligament injury with those with no history using the Kruskal-Wallis test.

RESULTS

Among the 1177 participants, 971 were male (age, 18.8 ± 0.9 years), and the remaining 206 were female (age, 18.7 ± 0.8 years). Normative median values and interquartile ranges (IQRs) for the KOOS scale scores among men with no history of knee ligament injury were the following: Symptoms (96.4; IQR, 10.7), Pain (100; IQR, 2.8), Functional Activities of Daily Living (ADL) (100; IQR, 0.0), Sports and Recreation Function (100; IQR, 5.0), and Knee-Related Quality of Life (QOL) (100; IQR, 12.5). For women with no history of knee ligament injury, the KOOS scale scores were the following: Symptoms (92.9; IQR, 14.3), Pain (100; IQR, 5.6), Functional ADL (100; IQR, 2.9), Sports and Recreation Function (100; IQR, 10.0), and Knee-Related QOL (93.8; IQR, 18.8). Among the men, 139 (14%) reported a history of knee ligament injury, while 33 (16%) women also reported a history of injury. All KOOS scale scores and the WOMAC Stiffness and Function scale scores were significantly lower (P < .05) for men who reported a history of knee ligament injury. Similarly, Symptoms, Pain, and Knee-Related QOL on the KOOS and Pain on the WOMAC were significantly lower among women with a history of knee ligament injury.

CONCLUSION

Normative values for all KOOS scales suggest a high level of functioning among participants with no history of knee ligament injury. Despite meeting the medical standards for military service, participants with a history of knee ligament injury had significantly lower KOOS and WOMAC scores upon entry to military service.