Immovable joints, also known as synarthrotic joints, are joints in the human body that do not move. Humans have immovable joints for stabilization and for ossification—the process of cartiladge turning into bone, usually seen only in children. While the human body does not have many immovable joints, they are very important for everything from chewing to infant development. There are three kinds of immovable joints: gomphosis, suture, and synchondrosis.
Gomphosis joints are where one bone fits into another and cannot move. The only example in the human body, according to Encyclopedia Britannica, is teeth. For this joint, a fibrous tissue connects the teeth to the sockets and keeps them in place. While this joint is immovable, steady, gradual pressure can forcibly move it, as in the case of braces, or with a sudden jerk, as in the case of an injury knocking out a tooth.
Sutures are defined as bones connected by fibrous seams, and are immovable. The only example in the human body is located in the skull, which, according to Sciencethinking.org, is made up of multiple seams. GetBodySmart.com highlights the four suture joints of the skull: the squamous suture, the sagittal suture, the coronal suture, and the lambdoidel suture. According to the Mayo Clinic, the fibrous tissues of the sutures are softer and spaced farther apart when a child is born. This is to allow the skull to grow as the brain expands, and is why one must be careful with a newborn’s head. As the child grows up, the joints fuse together and become rigid.
Synchondrosis is the term for a bone connecting to another bone with thick, fibrous tissue (usually cartilage). Of all the body’s immovable joints, they are the most numerous. According to Sciencethinking.org, United Nations University, and South Dakota State University, examples of synchondrosis are the tibiofibular joint, which is the connection between the tibia and fibula found near the knee; the sternocostal joint, which is the connection between the rib and sternum; the manubrium, which connects the sternum and clavicles; the connection between the ulna and the radius, found in the forearm; the pubic symphysis, found in the pelvis; the connection between the occipital and sphenoid bones, found at the base of the skull; and epiphyseal growth plates, which are lengths of cartilage that ossify and become bone as the person ages, most commonly found in long bones such as the tibia.