One cannot consider the synovial fluid without also defining the normal spaces of a joint. An open space must be maintained in both the upper and lower joint cavities so that synovial fluid can access the intra-articular structures for nutrition and lubrication. Ultimately, the superior space will be bounded by the attachments of the articular capsule medially, and laterally by the origination of the retrodiscal attachment posteriorly, and by the blending of epimysium, capsule and periosteum anteriorly. The capsule is primarily a medial and lateral joint structure. Medially, it will generally course along an area approximating the squamosphenosal suture line. Laterally, the capsule will originate from the inferolateral edges of the fossa and eminence. In the anterior of the upper joint cavity, the space will be limited generally to the eminence at its most prominent portion or slightly, onto the anterior slope of the eminence. This reflection comprises a blending of epimysium with the periosteum of the anterior eminence through an orifice of the capsule. As such, this boundary is usually obliquely oriented medially and anteriorly. There is no true capsule in the posterior portion of the TMJ. Therefore, the posterior boundary is limited by the posterior and superior origin of retrodiscal attachment. This tissue generally originates just anterior to the squamotympanic and petrotympanic fissures. The inferior joint cavity is bounded medially and laterally by the insertion of the medial and lateral collateral ligament onto the condylar surface. Anteriorly, this cavity is limited to the blending of capsule and tendon between the part of the superior belly of the lateral pterygoid muscle that inserts into the disc and the part that inserts into the condyle. Posteriorly, the retrodiscal tissues normally blend with periosteum approximately 10 mm down onto the neck of the mandibular condyle.