Knee pain dilemma and the initial step to predicting diagnoses in general practice: a cross sectional study

Introduction. Knee pain is a common reason to consult a general practitioner (GP), but accurate diagnosis poses a challenge for GPs. To support GPs with this diagnostic dilemma in patients with knee pain, a prediction model could be a useful diagnostic decision support tool. Aim. This study explores the most common diagnoses in patients with knee pain referred by their GP to a
primary care orthopaedic clinic, and if this diagnosis can be predicted by patients’ age. Methods. This was a cross-sectional study of medical records of patients with knee pain in the Netherlands, referred by their GP to a primary care orthopaedic clinic between January 2021 and June 2023.
Results. We included 627 patients with a mean age of 53.0 years (s.d. 16.9). Sixty-nine percent of
the patients were diagnosed with osteoarthritis of the knee, 9% were diagnosed with patellofemoral pain, followed by a meniscal lesion in 5%. The optimal age threshold is ≥49.5 years for knee osteoarthritis (area under the receiver operator curve (AUC: 0.90, 95% CI: 0.87–0.93), <47.5 years for patellofemoral pain (AUC: 0.87, 95% CI: 0.83–0.91), and <52.5 years for meniscal
lesions (AUC: 0.72, 95% CI: 0.64–0.81). Discussion. In a primary care population presenting with knee pain, in which GPs experience diagnostic challenges, an age threshold of roughly 50 years is a strong predictor for knee osteoarthritis, patellofemoral pain, and meniscal lesions, the three most common diagnoses. This study marks an initial step in simplifying the diagnostic process for
knee pain, aiming to illuminate the path to a more predictive diagnostic approach.