Myotendinous unit, also called muscle-tendon-bone or muscle-tendon-enthesis unit, is a complex structure, responsible for producing skeletal movement.
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Gross anatomy
Myotendinous unit consists of bone, enthesis, tendon, myotendinous junction and muscle. However, the presence of certain components is variable - for example, the muscle can attach to the bone directly, without a tendon.
The proximal osseous attachment of the myotendinous unit is called an origin, and the distal attachment - an insertion.
Radiographic features
Plain radiograph
Normally there is a smooth cortical outline in the attachment site of the enthesis, no cyst-like changes or bony proliferations should be present.
Ultrasound and MR
A normal tendon has a fibrillated pattern, which can be sometimes confused with tear because of the anisotropy (in ultrasound) or the magical angle artifact (in MR).
A normal muscle has a striated, feathery appearance, and well-defined boundary at the myotendinous and myofascial junction.
Clinical presentation
The myotendinous unit can be injured at various locations and the site of injury is affected by many factors, e.g. patient's age, mechanism of trauma, underlying conditions and concomitant drug use.
Related pathology
For pathology of a specific component of the myotendinous unit, please refer to the following articles: