Osteoarthritis of knee. Colour Magnetic Resonance Imaging (MRI) scan of a front view of the knee joint of a 33 year old male with osteoarthritis. The lower end of the femur (thigh bone) is at centre (blue); it articulates with the upper end of the tibia (shin bone) at lower centre (blue). Due to osteoarthritis the ends of the bones have become severely eroded and jagged; cracking of the bone is also visible. A deep intercondylar notch (triangular) has formed in the femur. Osteo- arthritis is the most common type of arthritis due mainly to wear and tear on joints in the elderly. This patient had haemophilia which was a factor.