Subclinical crystal arthropathy: a silent contributor to inflammation and functional disability in knees with osteoarthritis-an ultrasound study.

PURPOSE: This study aimed at investigating the prevalence of crystal deposits with knee osteoarthritis (OA) by ultrasonography and measure the inflammatory burden associated with crystal deposits in OA using WOMAC score. METHODS: Adult patients with primary knee OA diagnosed according to the American College of Rheumatology criteria were included. Participants were subjected to history taking, clinical examination, knee US, and plain radiography. The EULAR and the OMERACT ultrasonography definitions and scanning protocols were used. RESULTS: Fifty-three patients (44 females, 9 males) were enrolled. Mean values were 53.5 years ± 8.3 SD for age and 42.5 months ± 49.5 SD for disease duration. Crystals were detected by US in 73/106 knees (68.9%). Plain radiography revealed chondrocalcinosis in three patients. Mean values for WOMAC pain, stiffness, and disability scores were 14.38 ± 3.99, 4.93 ± 2.06, and 49.61 ± 13.06, respectively, with insignificant differences relative to presence of crystals (P > 0.05). Regression analysis revealed a 4.1-fold increase in the incidence of sonographic crystals with bursitis (OR = 4.13, CI = 1.5-11.2, p = 0.01) and a 3.2-fold increase in the incidence of sonographic crystals with synovial effusion (OR = 3.16, CI = 1.34-7.44, p = 0.01). CONCLUSION: Subclinical crystals were detected in a considerable number of patients with primary knee OA. The incidence of crystal deposits was significantly higher in patients with bursitis and knee effusion.