Because of its complex structure and weight-bearing capacity, the knee is the most commonly injured joint. Each year, more than 5.5 million people visit orthopedic surgeons for knee problems. More severe injuries include bone bruises or damage to the cartilage or ligaments. There are two types of cartilage in the knee. One is the meniscus, a crescent-shaped disc that absorbs shock between the thigh (femur) and lower leg bones (tibia and fibula). The other is a surface-coating (or articular) cartilage. It covers the ends of the bones where they meet, allowing them to glide against one another. The four major ligaments that support the knee are the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and the lateral collateral ligament (LCL). Common symptoms of knee injury are pain and swelling to the joint. Patients with a knee fracture will have pain while at rest, and with motion. Deformity is a symptom seen with knee fractures or dislocations. Patients with knee sprains tend to have swelling and pain that increases in the first 24 hours after the injury.

  While the term "shin splints" has been widely used to describe any sort of leg pain associated with exercise, the term actually refers to pain along the tibia or shin bone, the large bone in the front of the lower leg. This pain can occur at the front outside part of the lower leg, including the foot and ankle (anterior shin splints) or at the inner edge of the bone where it meets the calf muscles (medial shin splints).

  Shin splints are primarily seen in runners, particularly those just starting a running program. Risk factors for shin splints include overuse or incorrect use of the lower leg; improper stretching, warm up, or exercise technique; overtraining; running or jumping on hard surfaces; and running in shoes that don't have enough support. These injuries are often associated with flat (overpronated) feet.