Essential Physics for Manual Medicine

Essential Physics for Manual Medicine Figure 4.9 • Because discs are not visualized on plain film x-ray (A), magnetic resonance (MR) imaging is the modality of choice to assess damage to discs. (B) A sagittal T1-weighted MR image shows a disc extrusion on the left at L5 (arrow). (C) A T1-weighted axial image and (D), a T2-weighted sagittal image, demonstrate that the large paracentral extrusion is occluding the left lateral recess and compressing the anterior aspect of the thecal sac (arrows). The disc has also lost some of its height. Image reproduced courtesy of Michelle Wessely, IFEe, France © Clinical Chiropractic, 2006. The key feature of a synovial articulation is the glide smoothly across each other. As a consequence, joint space (in reality, more a potential than an most synovial joints have considerably more move­ actual space, particularly when weight bearing). ment than their fibrous and cartilaginous counter­ Unlike the two classes of joints that we have previ­ parts and are thus classified as diarthrodial. Their ously examined, there is no connecting tissue movement is restricted by the anatomical para­ between the two (or more) bones involved in a meters of the joint, the supporting ligaments and synovial joint. Instead, the joint is contained with the biomechanical limitations of the articulating a ligamentous capsule, the interior surface of which muscles. has cells that secrete synovial fluid, which acts to lubricate the joint's surfaces and allows them to The major classification system for synovial joints is based on the anatomical relationship 78