II. Causes: Trauma
- Ligament injury
-
Meniscus Injury
- Medial Meniscus Injury
- Lateral Meniscus Injury
- Patella injury
- Intra-articular Fracture
III. Causes: Rheumatic Conditions
IV. Causes: Infectious Disease
V. Causes: Malignant Tumor
- Hematologic Malignancy
- Chondroblastoma
- Eosinophilic Granuloma
- Giant cell tumor
- Ewing's Sarcoma
- Osteosarcoma
- Synovial Sarcoma
VI. Causes: Benign Tumor
- Aneurysmal bone cyst
- Fibrous cortical defect
- Fibrous dysplasia
- Osteochondroma
- Osteoid Osteoma
- Pigmented villonodular synovitis