Work

Association of calcium phosphate crystals with pain and inflammation among individuals with advanced knee osteoarthritis: A cross-sectional study

Year: 2026

Type: article

Abstract: Background Basic calcium phosphate (BCP) and calcium pyrophosphate crystals (CPP) are suspected to be part of osteoarthritis (OA) pathogenesis through chondrocyte-, fibroblast-, and leukocyte-mediated inflammation and cartilage destruction. We aimed to determine whether the presence of CPP and BCP in synovial fluid (SF) was associated with pain and inflammation in patients with knee OA. Methods SF was sampled during the baseline visit of the Intensive Diet vs. Knee Arthroplasty (INKA) trial. BCP and CPP were detected by Raman Spectroscopy (RS). Participants were classified as Calcium crystal positive (CaC+) or negative (CaC−). Pain was evaluated using the KOOS 12 Pain subscale. Ultrasound (US) was performed to evaluate medial and lateral synovial hypertrophy/effusion. Continuous and categorical outcomes were analysed using ANCOVA and logistic regression, respectively. Results Fifty-one participants from the INKA trial met the inclusion criteria; 49 samples were analysed using RS. All participants (n = 49) were calcite positive. 29 participants were calcium phosphate positive with BCP (n = 18), CPP (n = 3), or both (n = 8). Estimated between-group difference for KOOS 12 Pain was 8.7 points (95% CI: 0.2 to 17.5; P=00.054) with the CaC + group indicating higher KOOS 12 Pain scores (42.32 vs 33.64), i.e. less symptoms. Prevalence of US-detected inflammation was 97% (n = 28) in the CaC + group and 95% (n = 19) in the CaC− group. Estimated odds ratio was 0.85 (95% CI, 0.04 to 20.41; P=00.92). Conclusion BCP and CPP positivity in SF was neither associated with knee OA patients' symptoms nor US-detected inflammation.

Source: Osteoarthritis and Cartilage Open

DOI: 10.1016/j.ocarto.2026.100887