By the way, doctor: Is taking calcium a problem if you have pseudogout?
Q. I've been diagnosed with pseudogout, which I understand is caused by a buildup of calcium crystals in the joints. Should I be concerned about taking a calcium supplement?
A. Pseudogout is a type of inflammatory arthritis characterized by sudden attacks of pain and swelling in the joints. It closely resembles gout, hence the name. But gout usually affects a big toe, and pseudogout usually affects the knee, though both conditions can affect other joints as well. Gout is caused by sodium urate crystals, and pseudogout is caused by crystals of calcium salts — calcium pyrophosphate dihydrate, or CPPD.
CPPD crystals initially form in the cartilage and migrate into synovial fluid, stimulating inflammation in the joint. Most people with x-ray evidence of CPPD crystals never have symptoms, but some develop pseudogout, as well as chronic arthritis. We don't know why calcium crystals form in joints, but they may result from elevated levels of calcium or pyrophosphate or other factors that lead to supersaturation of calcium pyrophosphate in cartilage and bone.