Abstract

Associations between compartmental distribution of radiographic changes of osteoarthritis (OA), individual features of OA (joint space loss, sclerosis, cyst, osteophyte; each scored 0-3), and presence of synovial fluid calcium particles (calcium pyrophosphate dihydrate (CPPD) crystals identified by polarised light microscopy and other calcium particles by alizarin red positivity (ARP) were sought in 300 osteoarthritic knees (178 patients; mean age 72, range 33-96 years). Patients whose knees were symptom free as well as those with symptoms were included. Osteoarthritis of two or three compartments but not unicompartmental OA was associated with the presence of CPPD or ARP. Involvement of any compartment (not just patellofemoral), and higher mean scores for both total and individual osteoarthritis changes (except cysts) was associated with CPPD and ARP; CPPD, but not ARP, was associated with symptoms: knees reported as having symptoms had higher mean total OA scores. Femoral cortical erosion, found more often in women, was associated with higher mean total OA score at the patellofemoral compartment but not with the presence of particles. Attrition, remodelling, and chondrocalcinosis (each scored as present or absent) occurred more often in knees with CPPD. Age did not correlate with any aspect of the OA score. This study confirms the association of calcium particles with the process of OA. Unlike previous studies confined to symptomatic knees, a radiographic pattern specific to CPPD ('pyrophosphate arthropathy') did not emerge.