Predicting Knee Pain and Knee Osteoarthritis Among Overweight Women

There is a need for prediction of knee osteoarthritis (KOA) in general practice to motivate subjects for preventive therapies and optimize preventive trials.

To develop a prediction model, with questionnaire and physical examination variables, for incident frequent knee pain (FKP) and symptomatic KOA after 2.5 and/or 6.5 years among overweight and obese middle-aged women.

Models were developed in the Prevention of Knee Osteoarthritis in Overweight Females study (age 50 to 60 years, body mass index [BMI] ≥ 27 kg/m²) (ISRCTN 42823086). FKP was defined as knee pain during most days in the past month. Symptomatic KOA was defined according to the combined (clinical and radiographic) American College of Rheumatology criteria.

Multivariable analysis by backward stepwise deletion was performed for questionnaire and physical examination variables. The prediction model was externally validated in Rotterdam Study (RS)-III. Area under the curves (AUCs) of receiver operating characteristic were calculated.

32% of 237 women (mean age 55.7 ± 3.2 years; mean BMI, 31.9 ± 3.8 kg/m²) developed FKP and 30% developed symptomatic KOA. AUC of age and BMI was 0.63 (0.55 to 0.71) for incident FKP. The final model included age, BMI, mild knee symptoms, knee problems climbing stairs, morning stiffness, postmenopausal status, and heavy work. AUC was 0.71 (0.63 to 0.78). Results were similar for incident KOA. Applying external validation, similar results were observed in the RS-III.

In this study, easy-obtainable variables modestly improved the prediction of FKP and symptomatic KOA above age and BMI. To improve the identification of high-risk individuals, development of valid tests for other known risk factors, like meniscal damage, that are applicable in primary care, are urgently needed.