Correlation between synovial fluid calcium containing crystal estimation and varying grades of osteoarthritis created using a rabbit model: Potential diagnostic tool

Abstract Objectives Accurate diagnosis of osteoarthritis (OA) is the first important step in ensuring appropriate management of the disease. A multitude of tests involving assessment of biomarkers help in assessment of severity and grading of osteoarthritic damage. However, most tests are time consuming and are limited by the paucity in synovial fluid volume. In majority of OA effusions, calcium containing crystals are found. The aim of our study was to evaluate whether a correlation existed between the amount of calcium containing crystals present in synovial fluid and severity scoring of OA to propose a quick and inexpensive technique for disease assessment. Materials and methods Monosodium-iodoacetate was used to induce high- and low-grade knee OA in adult New Zealand white rabbits (n = 6 joint each group). At 16 weeks, synovial fluid and joints were harvested for histopathological analysis. OA grading was established based on OARSI scoring. Synovial fluid calcium crystal count was assessed by light microscopy (Alizarin red) and confirmed by Fluo-4, AM imaging and polarized microscopy. Statistical analysis was performed using unpaired Student t-test and Pearson correlation. Results and conclusion The clumps counted in low-grade OA were significantly lower than high-grade OA, in addition to showing a positive correlation (coefficient: 0.65; P=0.021) between calcium crystal count and the grade of OA created. Fluo-4, AM staining, and polarized microscopy were indicative of calcium pyrophosphate dihydrate crystals. This is the first study to suggest that Alizarin red could serve as an effective and rapid, bed-side method for screening and assessing disease progression.