Determination of normal KOOS and WOMAC values in a healthy population

Purpose: The KOOS questionnaire is used to assess the symptoms and function of patients with traumatic or degenerative knee pathology. The WOMAC score has been validated mainly in the context of knee osteoarthritis. The distribution of these scores in a non-diseased population is not known. The hypothesis was that KOOS and WOMAC scores were influenced by patients’ age, sex, and BMI. The primary objective of this study was to describe, for the first time, the distribution of KOOS and WOMAC scores in a healthy population based on age, sex, and BMI. Methods: This was a pilot (innovative), cross-sectional, international, multicenter, descriptive study. Persons accompanying patients to our clinic were invited to participate in this study by filling out the KOOS questionnaire. These data were also used to calculate the WOMAC score. The study was designed according to guidelines on pilot studies and planned to enroll a minimum of 30 subjects in each age, gender, and BMI group. Expected KOOS and WOMAC scores by age, gender, and BMI were determined using a linear regression model. Results: Seven hundred and fourteen subjects were included: 305 men (42.7%) and 409 women (57.3%). For the KOOS score, as age increases, there was a decrease in the “ADL” (p = 0.0001) and “sport” (p = 0.0001) items and an increase in the “symptoms” (p = 0.0025) and “QOL” items (p = 0.0001). Women had lower scores (p < 0.05) than men on all the KOOS items, except “QOL”. For the WOMAC, the “pain”, “stiffness”, and “function” items varied significantly based on age (p = 0.0203) and sex (p = 0.0121). The “stiffness” item varied significantly based on age (p = 0.0005) and sex (p = 0.0477). The “function” item varied significantly based on age (p = 0.0001) and sex (p = 0.0256). The expected value for the KOOS and WOMAC scores in a healthy population without any knee ailments were determined. Conclusions: The KOOS and WOMAC scores vary significantly based on age, sex, and BMI in a healthy population. This study also provides KOOS and WOMAC values in a population without any knee issue. These scores can be used, in a daily practice, as a reference to assess functional outcomes after a surgical procedure. Level of evidence: IV.