A shoulder dislocation (shoulder instability) occurs when the upper end of the arm bone pops out of the shoulder joint. This injury may be caused by a direct blow to the shoulder, a fall on an outstretched hand or arm, or an exaggerated overhead throwing motion.

Shin splints are an inflammation of the periosteum, a fibrous sheath that surrounds bone. In this case, the affected bone is the shin bone, or tibia. Shin splints are usually accompanied by pain and swelling in the front of the lower leg. Most frequent in runners, this overuse injury is caused by the repetitive stress of running on hard surfaces.

There are four ligaments in the knee: the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). The ACL and PCL stabilize front-to-back knee movements, while the MCL and LCL stabilize side-to-side movements.

The ACL can be sprained or torn if the knee is straightened beyond its normal limits (hyperextended), twisted, or bent side-to-side. A sprained or torn ACL is common in sports and usually results from a hard stop or aggressive twisting of the knee. The PCL is the least common ligament to be injured.

The MCL is injured when a force is exerted on the outside of the knee, pushing it inward, while the LCL is injured by a force exerted on the inside of the knee that pushes it outward. This type of hit is frequent in contact sports like football or hockey.

A torn knee ligament is usually accompanied by feeling or hearing a pop in the knee at the time of injury, severe pain and swelling, and joint instability.