A joint is the junction point between two bones. There are three categories of joints classified by the amount of movement they allow: fibrous joints which allow no movement, cartilaginous joints which allow limited movement, and synovial joints which are free-moving. A pivot joint, also known as a rotary joint, is a type of synovial joint in which a circular bone rotates upon the axis of another bone.
There are only three pivot joints in the human body: one in the neck at the base of the skull and one in each elbow. The pivot joint in the neck, called the atlanto-axial joint, allows the head to rotate back and forth and from side to side. Trauma, infections, arthritis, syndromes and some diseases can cause instability in this area. Down syndrome is one such example; people with Down’s tend to have looser ligaments, including those around this pivot joint. Instability in this area needs to be watched because all of the nerves passing between the brain and spine lie near this joint and can be damaged if instability is pronounced.
Just like any other joint, the atlanto-axial joint can be affected by osteoarthritis or injury, which can result in chronic neck pain and headaches. Injection therapy is a treatment option which can offer significant pain relief for extended periods of time. These injections are performed in an outpatient setting and do not require sedation. The pivot joint found in the elbows is called a proximal radioulna, and is one of three joints found in the elbow. It is formed by the radius and the ulna, the smaller of the two bones in the lower arm. This joint makes it possible for the hand to rotate.
In rare cases a condition known as proximal radioulna synotosis can occur. This happens when the bones composing the pivot joint in the elbow have become fused together, decreasing or eliminating the joint’s movement. There have been a few documented cases of congenital synotosis, presumably caused by a malformation of the bone structure in utero. While the disorder is present at birth, it is not usually diagnosed until adolescence when the child has grown to a point that the limited mobility is more apparent and the condition has become painful.
Most cases of proximal radioulna synotosis are a result of some trauma, such as a fracture of one of the bones in the forearm which has been surgically repaired. In instances where screws or bone grafts have been required, the bones in the pivot joint can begin to fuse together. This condition is not usually treated surgically unless movement is severely limited. Successful remediation depends upon the degree of synotosis and how long the condition has existed.