Objective    To explore the effectiveness and the feasibility of establishment of osteoarthritis animal model by arthroscopy and monitor the osteoarthritis lesion of bone and cartilage by magnetic resonance imaging (MRI) in bilateral knee joints of mini-pigs.     Methods    Bilateral partial menisci resections were performed on four mini-pigs (8 joints) by arthroscopy. Changes of bone and cartilage contacted with the resected menisci were analyzed by gross observation

histology

and MRI at 12 weeks after surgery.     Results    Gross observation showed focal fibrillation on articular cartilage surfaces and significant osteophyte formation at lateral intercondylar notches of the distal femur. Histology revealed the loss of cellularity and proteoglycan and increase in the number of clustering-arrayed chondrocytes. MRI showed the cartilage thickness was decreased and signal intensity of bone and cartilage changed.     Conclusion    Osteoarthritis animal models in bilateral knee joints of mini-pigs can be established effectively by partial meniscectomy under arthroscope. Changes of bone and cartilage of osteoarthritis animal models can be monitored sensitively by MRI.