Basic calcium phosphate deposition in the joint: a potential therapeutic target in osteoarthritis

Detection of calcium phosphate crystals in the joint fluid of patients with osteoarthritis - analytical approaches and challenges

Clinically, osteoarthritis (OA) is characterised by joint pain, stiffness after immobility, limitation of movement and, in many cases, the presence of basic calcium phosphate (BCP) crystals in the joint fluid. The detection of BCP crystals in the synovial fluid of patients with OA is fraught with challenges due to the submicroscopic size of BCP, the complex nature of the matrix in which they are found and the fact that other crystals can co-exist with them in cases of mixed pathology. Routine analysis of joint crystals still relies almost exclusively on the use of optical microscopy, which has limited applicability for BCP crystal identification due to limited resolution and the inherent subjectivity of the technique. The purpose of this Critical Review is to present an overview of some of the main analytical tools employed in the detection of BCP to date and the potential of emerging technologies such as atomic force microscopy (AFM) and Raman microspectroscopy for this purpose.

Calcium crystal deposition and osteoarthritis

Calcium crystals are common and under-recognized participants in osteoarthritis. Excellent evidence supports two hypotheses explaining the relationship between calcium crystal deposition and osteoarthritis. There is ample support for the theory that calcium crystals cause or worsen osteoarthritis and equally compelling evidence to support the theory that osteoarthritis causes or worsens calcium crystal formation. Further research in this area will improve understanding of the pathogenesis of these conditions and should lead to the development of effective therapy for all types of degenerative arthritis.