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Bensa_2026_Elsevier_j.jcjp.2025.100282
Journal article

Pain trajectory, peaks, and regression to the mean in untreated patients with symptomatic knee osteoarthritis

  • Previtali, Davide Service of Orthopaedics and Traumatology, Department of Surgery, EOC, Lugano, Switzerland
  • Bensa, Alessandro ORCID Service of Orthopaedics and Traumatology, Department of Surgery, EOC, Lugano, Switzerland - Faculty of Biomedical Sciences, Università della Svizzera italiana, Switzerland
  • Boffa, Angelo Dipartimento di Scienze Biomediche e Neuromotorie, Alma Mater Studiorum Università di Bologna, Italy
  • Filardo, Giuseppe ORCID Service of Orthopaedics and Traumatology, Department of Surgery, EOC, Lugano, Switzerland - Faculty of Biomedical Sciences, Università della Svizzera italiana, Switzerland
  • 2026
Published in:
  • Journal of Cartilage & Joint Preservation. - 2026, p. 100282
Knee
Osteoarthritis
Pain peaks
Pain trajectories
Regression to the mean
English Introduction: Pain remains the predominant symptom and primary treatment target in knee osteoarthritis (OA). Objectives: This study aimed to document pain evolution patterns in untreated knee OA patients by assessing the prevalence and frequency of pain peaks and estimating regression to the mean. Methods: Patients with symptomatic, radiographically confirmed knee OA (Kellgren-Lawrence grade ≥ 2), completed baseline questionnaires and rated their pain twice daily using a smartphone app over 60 days, enabling Ecological Momentary Assessment. Group-Based Trajectory Modeling identified pain trajectories over 30 and 60 days. Baseline differences and trajectory characteristics were compared, pain peaks analyzed, and regression to the mean calculated as the difference between baseline and 2-month pain scores. Results: Of 156 patients enrolled, 140 completed the assessment. Three trajectory patterns emerged: stable, decreasing, and increasing pain, comprising 69%, 22%, and 9% (30-day analysis), and 65%, 11%, and 24% (60-day analysis) of patients, respectively. Notably, 16% shifted from stable to increasing pain during the second month. The stable group showed fewer pain peaks and fluctuations, while the decreasing group had worse baseline scores. Pain peaks occurred in 40% of patients at a frequency of more than 1 every 2 weeks. Regression to the mean was significant only in the decreasing pain subgroup (−0.43 ± 3.16; P < .001). Conclusions: Pain in untreated knee OA follows 3 main short-term trajectories: stable (65%), decreasing (11%), and increasing (24%). Pain peaks are common, especially in unstable trajectory groups. Regression to the mean was observed only in patients with initially higher pain levels and decreasing trajectory.
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Language
  • English
Classification
Medicine
License
CC BY
Open access status
gold
Identifiers
Persistent URL
https://n2t.net/ark:/12658/srd1335511
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