Crystal identification in human synovial fluids. Methods and interpretation.

Gout is largely solved, both from diagnostic and therapeutic standpoints. Acute gout is easily suppressed and joint destruction can be prevented and at least reversed by lowering the serum uric acid level with relatively safe and very effective drugs. But the arthritides associated with the calcium-containing crystals remain untreatable by other than symptomatic or surgical means. If we had a method or a drug to remove CPPD or BCP crystal deposits from joints, would it make any difference in the severity of the arthritis? Which of the paradigms shown in Figure 5 holds for these crystals? If joint damage directly follows crystal deposition as in gout, then crystal removal should prove prophylactic. The unusual pattern of joint degeneration associated with polyarticular CPPD crystal deposition and the initial appearance of CPPD crystals in radiographically normal cartilage favors this idea. But radiologic chondrocalcinosis appearing in knees subjected years before to meniscectomy but not in the contralateral knees suggests that crystal deposition, in these cases at least, is secondary to trauma or surgery. If degeneration of cartilage precedes crystal deposition, as it probably does in the case of BCP crystals, then crystal removal may not be particularly helpful. Dieppe and his colleagues proposed that the calcium crystals provide a positive feedback (amplification) loop. This represents the minimalistic view of their importance. The biologic consequences of the calcium crystal deposition diseases are now being explored at the molecular level. Much more data are needed before more than speculative answers to the questions posed here can be formulated. Calcium crystal deposition is more common in older persons. The degenerative and destructive arthropathies associated with them will predictably become increasingly common as our population ages.