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A Measure to Predict Knee OA and Frequent Knee Pain in Overweight Women

Beyond age and BMI, researchers obtained several key risk factors.

A PPM Brief

Predicting knee osteoarthritis (OA) in patients is important for practitioners to motivate subjects to participate in preventive therapies early. While risk factors for both frequent knee pain (FKP) and knee OA may include old age, female gender, and overweight/obesity, not all women with these characteristics develop the condition. Therefore, in a recent study,1 researchers from the University Medical Center in Rotterdam, The Netherlands, developed a prediction model, with both questionnaire and physical examination variables, for the incidence of FKP and symptomatic knee OA after 2.5 and/or 6.5 years among overweight and obese middle-aged women.

Researchers used data from the Prevention of Knee Osteoarthritis in Overweight Females (PROOF) study, a randomized controlled trial of 407 overweight and obese women of 50 to 60 years in general practices in Rotterdam. PROOF evaluated the preventive effects of a tailor-made diet and exercise program and of oral glucosamine sulfate versus placebo on the development of knee OA over 2.5 years. Post-hoc long-term outcome evaluation was performed over 6.5 years’ follow-up. Participants were recruited by their general practitioner (GP) and had to be free of knee OA according to American College of Rheumatology (ACR) criteria.

Predicting knee pain and knee osteoarthritis among overweight and obese women. (Source: 123RF)

Further inclusion criteria were:

  • BMI greater than or equal to 27 kg/m2
  • no inflammatory rheumatic diseases
  • no severely disabling comorbidities
  • not under treatment of a physical therapist or GP for knee complaints
  • not using walking aids
  • not using oral glucosamine for the past 6 months

At baseline, participants filled in a questionnaire and underwent standardized physical examination. Baseline posterior-anterior radiographs of both knees were taken using a semiflexed metatarsophalangeal protocol. Measurements were repeated after 2.5 and 6.5 years; only women participating at 2.5 years were asked to participate at 6.5 years.

Results indicated that:

  • Seventy-five of 237 women (32%) developed FKP and 70 of 235 (30%) developed symptomatic knee OA. Area under the curve (AUC) of age and BMI was 0.63 (0.55 to 0.71) for incident FKP. Within those with incident FKP (n = 75), 93% (n = 70) had a tibiofemoral osteophyte ipsilateral.
  • The following predictors for knee OA, and similarly for FKP, were chosen based on selection criteria: age, BMI, mild knee symptoms, knee problems while climbing stairs, morning stiffness, postmenopausal status, and physically demanding work. AUC was 0.71 (0.63 to 0.78).

In the study, these easily obtainable variables modestly improved the prediction of FKP and symptomatic knee OA above age and BMI. “Since the discriminative ability of the prediction models was moderate, the prediction of FKP and symptomatic knee OA seems not yet clinically applicable,” the researchers concluded.

Therefore, according to the team, development of valid tests for other known risk factors are needed. “It might be worthwhile to obtain other variables that can discriminate in high-risk subjects,” the researchers wrote. “We did not include, for instance, known risk factors for incident knee OA like malalignment, meniscal damage or effusion synovitis.”

Last updated on: September 20, 2019
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