The elbow is the joint where the three bones of your arm meet in the middle. The bone of the upper arm (humerus) meets the inner bone of the forearm (ulna) and the outer bone of the forearm (radius) to form a hinge joint at the olecranon (elbow). The radius and ulna also meet at the elbow to allow for rotation of the forearm. The elbow functions to move the forearm like a hinge (forward and backward) and in rotation (twisting outward and inward).
The bicep muscle is the major muscle that flexes the elbow, while the tricep muscle is the muscle that extends the elbow. The outer bone of the elbow is referred to as the lateral epicondyle and is a part of the humerus bone. Tendons are attached to this area which can be injured, causing inflammation or tendinitis (lateral epicondylitis, or “tennis elbow”). The inner portion of the elbow is a bony prominence called the medial epicondyle. Additional tendons from the muscles attach here and can be injured, causing medial epicondylitis, or “golfer’s elbow.”
A fluid-filled sac (bursa), which serves to reduce friction, overlies the tip of the elbow (olecranon bursa). The elbow can be affected by inflammation of the tendons or the bursae (plural for bursa) or conditions that affect the bones and joints. Joint pain in the elbow can result from injury or disease involving any of these structures.
A common elbow ligament that gets injured – especially in throwing athletes – is the ulnar collateral ligament, or the UCL. This ligament runs along the inside of the arm (closest to the body), across the elbow. It often gets overused, resulting in chronic pain to the inside of the elbow. It can also tear and may need to be surgically repaired. In baseball pitchers especially, this is often referred to as Tommy John’s surgery.
However, there is a point that ligaments and muscles can be injured just by being stretched too far, and this is called a sprain. Sprains and strains are other common injuries that can occur to the elbow joint as it is likely to be overused.