Cartilage is the smooth, rubbery tissue that covers the ends of your bones and helps them move smoothly. Arthritis is a general term covering numerous conditions where this cartilage wears out. When the articular cartilage wears out, the bone ends rub on one another and cause pain. Knee arthritis is a condition that damages the cartilage in your knee joint.
A knee fracture is a break in the bone of your knee. Your knee has three bones: the thighbone (femur), shinbone (tibia), and kneecap (patella), and a fracture can occur in any of these bones. In younger individuals, these fractures are caused by high-energy injuries, such as a motor vehicle accident or a sports injury. In older people, the most common cause is weak and fragile bones.
Soft tissue injuries to the knee are extremely common, especially in athletes. The knee is a complex joint, and it is supported by several ligaments and tendons. These structures can be damaged by a sudden impact or by overuse. Common soft tissue injuries to the knee include meniscal tears and ligament injuries.