Hello. It is a very normal to hear a cracking sound in a joint. It may not due to any disease. It is due to the changes in pressure in the fluid within the joint, and nitrogen gas comes out of the solution with a crack. One very common cause of joint Cracking is something called patellofemoral pain syndrome, or runner s knee . This is basically an overuse injury in which the cartilage on the back of the knee cap becomes roughened and clicks as it glides over the bone underneath. If you are diagnosed with this condition, it can be treated with 1. rest 2. strengthening exercises 3. anti inflammatory medications like Ibubrufen Thus nothing to worry about this. Hope this helps. Please write back for further queries. Wishing you good health.