There can be different crystals - CPPD (calcium pyrophosphate) or urate, calcium etc. that can accumulate. Depending on the type of crystals, the treatment differs; if you have arthritis, then apart from the treatment of crystals, the arthritis needs treatment in the form of medications or, if required, surgical intervention. If you have effusion (swelling in the joint) you may need to get fluid aspirated and analysed for crystals and cell counts.