Hello, Thanks for your query. Sometimes as a normal phenomena, fluid (synovial fluid) that lubricate the joint release bubbles which pop and crackle with movement. This occurs very commonly after a period of inactivity or during certain movements. I am not sure if this is what you have, but this is my most likely explanation to your symptoms. You don t need to worry if there is no associated joint pain; but you have to do some conditioning exercises to improve the overall integrity of the joint - stronger muscle will take the weight of the joint and help to reduce the pressure on articulating surfaces, thus preventing any damage to the joint. I do hope that you have found something helpful and I will be glad to answer any further query. Take care