The elbow is classed as a hinge-type synovial joint connecting the upper arm to the forearm. It is made up of three bones, the humerus, ulna, and radius and the ends of these bones are all covered with cartilage. Cartilage has a rubbery consistency that allows the joints to slide easily against one another and absorb shock. The bones are held together with ligaments that form the joint capsule. The joint capsule is a fluid filled sac that surrounds and lubricates the joint.
The important ligaments of the elbow are the medial collateral ligament (on the inside of the elbow) and the lateral collateral ligament (on the outside of the elbow.) Together these ligaments provide the main source of stability for the elbow, holding the humerus and the ulna tightly together. A third ligament, the annular ligament, holds the radial head tight against the ulna.
Most elbow injuries that bring people to the doctor are caused by repetitive strain, either from athletic injuries or other forms of overuse.
