TENDONDS
Sonoanatomy
On ultrasound tendons usually display a hyperechoic fibrillar pattern.
In transverse axis the tendon looks like “pepper and salt” – mass of hyperechoic granules alternating with hypoechoic granules of the same size, evenly distributed. In longitudinal axes a healthy tendon looks like “spaghetti”.
When the tendon is not perpendicular to the insonation angle anisotropy can cause artifactual appearance resembling tendinosis or tendon tears.
Transverse – Salt and pepper
Longitudinal – Spaghetti
Pathologies
Tendinopathy
Definition: A clinical term used to describe painful conditions of the tendon or tendon sheath including tendinosis, tendinitis and tendon tear.
US appearence: various
Tendinosis
Definition: Chronic tendon condition characterised histologically as collagen degeneration (predominantly mucoid) with collagen disorganisation, fibrocartilaginous metaplasia, calcification and possible neovascularity. Primarily an overused and degenerative process without an acute inflammatory infiltrate, but inflammatory mediators may be present.
US appearence: Abnormally hypoechoic tendon without tendon fibre disruption, with possible increase in tendon diameter, with or without flow on Doppler imaging.
Tendinitis
Definition: Inflamation of the tendon
US appearence: Abnormally hypoechoic tendon occasionally associated with possible increased flow on Doppler imaging. Imaging features of tendinosis and tendinitis are similar and may be present concurrently. Hyperaemia, as seen in tendinosis, is due to neovascularity and should not be equated with acute inflammation. Clinical features (history of inflammatory disease) may be required to determine the most likely histological diagnosis.
Calcific tendinopathy
Definition: Calcium deposition within a tendon; if calcium hydroxyapatite, this may be termed calcific tendinosis. Use calcific tendinitis when in the resorptive or inflammatory stage.
US appearence: Calcium hydroxyapatite appears as a globular well-defined hyperechoic focus within a tendon with variable shadowing.
Tenosynovitis
Definition: Inflammation of the tendon synovial sheath.
US appearence: Distention of a tendon sheath from fluid of variable echogenicity with or without synovial hypertrophy and possible increased flow on Doppler imaging. Some tendon sheaths normally communicate with joints (ie, long head of the biceps brachii tendon sheath and glenohumeral joint). Simple fluid within the tendon sheath may be secondary to intra-articular pathology rather than tenosynovitis.
Stenosing tenosynovitis
Definition: A subtype of tenosynovitis that affects tendons that course through osteofibrous tunnels composed of bone covered by a pulley or retinaculum. The hallmark is thickening of the pulley or retinaculum that causes constriction. Examples is trigger finger and de Quervain tenosynovitis.
US appearence: Hypoechoic thickening of pulley or retinaculum with possible hyperaemia on Doppler imaging with possible additional findings of tendinosis and tenosynovitis.
Paratenonitis
Definition: Inflammation and fibrosis of the paratenon surrounding a tendon that does not have a tenosynovial sheath (i.e. the Achilles tendon).
US appearence: Focal or diffuse abnormal hypoechogenicity surrounding a tendon with possible increased flow on Doppler imaging. Several related terms have been described in the literature (paratendonitis, peritenonitis and peritendinitis, paratenopathy, among others).
Tear
Definition: Disruption of tendon, categorised as partial thickness (interstitial/intrasubstance, bursal or articular (if relevant)) or full thickness (focal or full width/complete); a longitudinal split tear may also be described, typically when involving a tubular tendon.
US appearence: Hypoechoic or anechoic tendon fibre disruption with an extent defined by the categories listed in the definition. With longitudinal tears, the hypoechoic or anechoic abnormality is parallel to the long axis of the tendon.
Avulsion
Definition: Tendon tear at its bony attachment or a fracture at a tendon attachment.
US appearence: Variable depending on specific pathology.
Mnemonics and metaphors
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