This medical exhibit depicts the anterior displacement of the temporomandibular joint, or TMJ, from the LEFT side. Two illustrations of a lateral (side) view of the skull show the mandible (jaw) open and closed, revealing the displacement of the TMJ meniscus. To the immediate right are two enlarged cut-away sections of the dysfunctional TMJ showing the area in more detail. Labeled structures include the pterygoid muscle, mandible, temporal bone, meniscus, condyle and joint capsule...What is the Temporomandibular Joint (TMJ)?..The temporomandibular joint (TMJ) connects the lower jaw, called the mandible, to the temporal bone at the side of the head. If you place your fingers just in front of your ears and open your mouth, you can feel the joint on each side of your head. Because these joints are flexible, the jaw can move smoothly up and down and side to side, enabling us to talk, chew and yawn. Muscles attached to and surrounding the jaw joint control its position and movement. ..When we open our mouths, the rounded ends of the lower jaw, called condyles, glide along the joint socket of the temporal bone. The condyles slide back to their original position when we close our mouths. To keep this motion smooth, a soft disc lies between the condyle and the temporal bone. This disc absorbs shocks to the TMJ from chewing and other movements. ..Today, researchers generally agree that temporomandibular disorders (TMDs) fall into three main categories: ..ï myofascial pain, the most common form of TMD, which is discomfort or pain in the muscles that control jaw function and the neck and shoulder muscles; ..ï internal derangement of the joint, meaning a dislocated jaw or displaced disc, or injury to the condyle; ..ï degenerative joint disease, such as osteoarthritis or rheumatoid arthritis in the jaw joint. ..A person may have one or more of these conditions at the same time. ..Causes of TMD..Severe injury to the jaw or temporomandibular joint can cause TMD. A heavy blow