Final answer:
Synovial joints have a synovial cavity that allows more movement compared to cartilaginous and fibrous joints which lack such a space. Jaw synovitis is inflammation of the synovial membrane, whereas jaw capsulitis involves inflammation and stiffening of the articular capsule, often leading to reduced movement and pain.
Step-by-step explanation:
The main structural difference between synovial joints and cartilaginous and fibrous joints is the presence of a joint cavity. Synovial joints like the temporomandibular joint (TMJ), have a synovial cavity filled with fluid that enables a higher degree of movement. In contrast, cartilaginous joints, such as synchondroses and symphyses, and fibrous joints lack this space, limiting their mobility.
Jaw synovitis involves inflammation of the synovial membrane, which lines the synovial cavity of the TMJ, while jaw capsulitis, also known as adhesive capsulitis or "frozen jaw", refers to inflammation and potential fibrotic changes to the articular capsule of the joint leading to significantly reduced jaw movement.
Temporomandibular joint disorders may result from various factors, such as arthritis, cartilage wear, muscle fatigue, grinding of the teeth, or jaw injury. These disorders can cause symptoms such as pain, headache, difficulty chewing, and jaw immobility, and are often treated with pharmacologic agents or therapies like bite guards.