A strain occurs when a muscle is stretched or torn. A sprain occurs when a ligament is stretched or torn.

Strains are often the result of overuse or improper use of a muscle, while sprains typically occur when a joint is subjected to excessive force or unnatural movements (e.g., sudden twists, turns, or stops). Sprains can be categorized by degree of severity:

• A first-degree sprain stretches the ligament but does not tear it. Symptoms include mild pain with normal movement.
• A second-degree sprain is characterized by a partially torn ligament, significant pain and swelling, restricted movement, and mild to moderate joint instability.
• In a third-degree sprain, the ligament is completely torn with mild to severe pain, swelling, and significant joint instability.

Lateral epicondylitis, commonly known as tennis elbow, is inflammation of the tendon that connects the muscles of the forearm, wrist, and hand to the upper arm at the elbow. The tendon on the bony outside (lateral) part of the elbow (the epicondyle) is most often irritated by overuse during physical activity.

Tendinitis is inflammation of a tendon, a band of tissue that connects muscle to bone. It is most commonly the result of overuse during physical activities. Repetitive motions can stretch and irritate the tendon, causing pain and swelling. Tendinitis occurs around joints such as the elbow, shoulder, wrist, ankle, or knee.

Impingement syndrome is a common disorder of the shoulder that refers to an improper alignment of the bones and tissues in the upper arm. Inflammatory conditions such as tendinitis, bursitis, and arthritis are all closely related to impingement syndrome, as are tears to the rotator cuff tendons.

If the rotator cuff becomes inflamed from overuse or there is a bone deformity or spur on the end of the shoulder blade, then the space between the upper arm bone and tip of the shoulder blade is narrowed, causing the rotator cuff and its fluid-filled bursa to be squeezed or pinched. This impingement causes irritation and pain to the rotator cuff when the shoulder is raised.