Most people believe it is caused by traumatic osteochondral fractures or repeated grade I trauma leading to vascular impairment, resulting in osteochondral necrosis and detachment. Some also suggest associations with bacterial emboli, fat embolism, terminal stirred pulse, or familial inheritance. The fragments include cartilage and the underlying bone. The fragments may be connected to the parent bone by a fibrous stalk or may be free-floating. The separation surfaces between the parent bone and fragments are covered with fibrous tissue or fibrocartilage, along with some new bone formation. Completely free fragments, nourished by synovial fluid absorption, continue to grow. The size and number of loose bodies vary and may lead to joint locking. Stalk rupture can cause intra-articular hematoma, and joint wear may result in proliferative arthritis.

bubble_chart Clinical Manifestations

It commonly occurs in males aged 16 to 25, frequently affecting the knee and elbow joints, but can also involve the hip, shoulder, ankle, or metatarsal joints. Typically, it affects a single joint without systemic symptoms. Symptoms may include dull joint pain that worsens with activity and improves with rest, along with mild joint swelling. Loose bodies may lead to joint locking, hematoma, and traumatic arthritis. Examination may reveal joint swelling, effusion, tenderness, palpable masses, limited movement with crepitus, and muscle atrophy. Lesions can occur on the medial and lateral femoral condyles, patellar articular surface, lateral humeral condyle, radial head, or the medial superior aspect of the talus in the ankle joint, often eliciting tenderness.

Since the fragments are mainly cartilage, early X-rays often show no findings. If the fragments are large, defects or translucent boundaries on the joint surface may be visible. Therefore, loose bodies are usually smaller than their actual size (due to the surrounding cartilage edge). In advanced stages, proliferative changes occur in the joint.

bubble_chart Treatment Measures

Non-separated fragments are treated with non-surgical therapy for 3 to 6 months, such as gypsum fixation, quadriceps exercises, and taking vitamin C, D, and calcium tablets. Non-surgical therapy has relatively good efficacy for children under 16 years old, but poor results for adults. Free bodies should be surgically removed early to avoid joint injury.

bubble_chart Differentiation

It should be differentiated from aseptic necrosis of the bone end and early marginal bone subcutaneous node.