Musculoskeletal ImagingTendon
a fibrous cord of collagen at the end of a muscle by which the muscle is attached to bones or other structures; the site of attachment is termed an
enthesis. Tendons help transmit muscle tension to facilitate movement, and as flexible cords they can be angulated about bone protuberances and change the direction or pull of muscles. A
synovial sheath may surround portions of a
tendon.
Numerous diseases and abnormal conditions may involve tendons; some of these, such as inflammation (tendinitis) or tears, are described under those headings or under the name of the specific tendon (e.g. Achilles tendon).
In calcium hydroxyapatite crystal deposition disease, recurrent painful calcific deposits in tendons, termed calcific tendinitis, are characteristic, especially about the shoulder. Calcification may also occur in various tendons (Achilles, triceps surae, quadriceps, supraspinatus) in persons with calcium pyrophosphate dihydrate crystal deposition disease.
Ossification of the Achilles tendon is also known to occur but is rare.
Trauma to tendons may result in ruptures or tears, although spontaneous tendon ruptures are a known manifestation of rheumatoid arthritis and have occurred in some patients after renal transplantation or dialysis or in persons with hyperparathyroidism, systemic lupus erythematosus or renal osteodystrophy. Tendon ruptures may also occur after chronic inflammation or as a consequence of corticosteroid therapy. MR imaging is valuable in defining interruption of involved tendons and presence of inflammatory tissue (Fig.1) (Fig.2).
Other abnormalities involving tendons include tenosynovitis, tethering, dislocations, tumours, pseudotumours, ossification, congenital anomalies, contractures and iatrogenic injuries.
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Sagittal fast spin-echo T2-weighted MR image of the ankle demonstrates a retracted, complete tear of the Achilles tendon.
(Courtesy of Vivian Lim, MD, La Jolla, CA)
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Tendon, Fig.1 | | Tendon, Fig.2 | |