Intra-articular inclusions of the cervical synovial joints.

Two hundred and ten cervical synovial joints from 15 adult vertebral columns were studied by dissection to determine the form, dispositions and prevalence of intra-articular inclusions. Three types of inclusions were found. Fat pads occurred regularly in the atlanto-occipital joints but rarely in the zygapophysial joints. Capsular rims occurred occasionally at all levels. Fibro-adipose meniscoid occurred regularly in the atlanto-axial and zygapophysial joints. The function of fibroadipose meniscoids seems to be to protect the articular cartilages in gliding joints that subluxate during normal movement. Arguments are raised that these structures may act as a nidus for intra-articular fibrosis, and that meniscus extrapment may be a mechanism for torticollis.