LOOSE BODY can result from a variety of pathological processes. Use of the term "loose" is frowned upon by some because the fragments do not rattle around in the knee so the term intra-articular fragment is a better nomenclature. Patients may be entirely asymptomatic but usually complain of pain, clicking, catching, locking, swelling, sensation something moving in and out of place or at times may feel something firm just beneath the skin of the knee.
These loose bodies are composed of cartilage or small pieces of bone covered with cartilage that can grow similar to a pearl in an oyster. After they are disrupted from the articular surface these intra-articular loose pieces derive nutrition from the synovial fluid in the knee. The surface cells named chondrocytes form more layers of articular cartilage therefore enlarging the loose body over time. The deeper cells received less and less nutrition resulting in death and calcification.
It is recommended that these loose pieces be removed arthroscopically and care given to their source. A wide range conditions can lead to development of intra-articular loose bodies from osteochondral fractures, osteochondritis dissecans, pigmented villonodular synovitis, osteoarthritis, synovial osteochondromatosis, neuropathic joints, and meniscal fragmentation with its calcification.