Loose bodies are a condition that is typically caused by trauma, inflammatory diseases, or repetitive stress. Loose bodies are fragments of bone or cartilage that break off and move around freely in the knee’s synovial fluid. If not treated properly, these fragments may cause damage to the articular cartilage, resulting in an increased chance of developing arthritis. Along with instability, you may experience knee pain and swelling until you undergo treatment. Although nonsurgical treatment may help with alleviating pain, surgery is the only way to remove the loose bodies from the joint.