Musculoskeletal Imaging

Ankylosis

consolidation and immobility of joints occurring as a result of disease, surgery or injury. Ankylosis can be classified as:

  • true or bony ankylosis, in which the bones of the joint fuse after proliferation of bone cells, resulting in complete immobility; or

  • false or fibrous ankylosis, in which proliferation of fibrous tissue results in partial joint immobility.

    An extracapsular ankylosis may also occur when joint movement is limited due to rigidity of structures outside the joint capsule (Fig.1). Surgical or artificial ankylosis is also known as arthrodesis.

    Among the many diseases in which joint ankylosis occurs are ankylosing spondylitis, degenerative joint disease, scleroderma, gout and myositis ossificans progressiva. It also occurs after immobilization or thermal burns.

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    Fig.1

    a. Frontal view of the chest in a patient with myositis ossificans progressiva demonstates extensive heterotopic ossification, including ossification that bridges the humeri and ribs. b. Frontal radiograph of the knees in the same patient demonstrates soft tissue ossification that bridges the right knee joint resulting in ankylosis.
    Ankylosis, Fig.1 (a)
    Ankylosis, Fig.1 (b)