Calcium hydroxy apatite is another crystal which can give rise to morbidity. One of its manifestations is acute periarthritis the joint commonly involved is the
a. Crystalline calcium hydroxy apatite is a normal component of bone mineral. It also occurs abnormally in dead or damaged tissue.
b. Minute deposits in joints or periarticular tissues can cause either an acute reaction or a chronic destructive arthropathy. In acute or subacute periarthritis which is by far the commonest of type the joint most commonly affected is the shoulder and then the knee