Ultrasound of the Achilles Tendon: Tendinopathy, Tears, Enthesopathy, and Neovascularization

Tendinopathy (Tendinosis)

Chronic Achilles tendinopathy is assessed via ultrasound in comparison with MRI and surgical data (Astrom et al., 1996). In severe tendinosis and interstitial tears, the appearance may mimic a partial tear, requiring careful interpretation.

Neovascularization on Doppler

Color and power Doppler are used to assess the microvascular response in Achilles tendinopathy; the distribution of microvascularization was studied using color and power Doppler (Richards et al., 2005). The role of vasculo-neural invasion as a cause of pain in chronic Achilles tendinosis is discussed, which was investigated using ultrasound and color Doppler, immunohistochemistry, and diagnostic injections (Alfredson et al., 2003).

Partial Tear

A partial tear of the Achilles tendon may initially appear as a more clearly defined hypoechoic or anechoic zone or gap, partially disrupting the tendon integrity, although severe tendinosis and interstitial tears may appear similar. A partial tear in addition to underlying tendinosis is indicated by tendon thickening greater than 1 cm and significant internal pathological changes. Partial tears may involve the musculotendinous junction.

Complete Tear and Dynamic Assessment

In tears at the musculotendinous junction, dynamic ultrasound with dorsiflexion and plantarflexion of the foot is used to demonstrate tendon continuity and rule out complete tears.

Enthesopathy

When identifying enthesophytes in the distal Achilles tendon, ordinary degenerative enthesopathy should not be confused with inflammatory. Inflammatory enthesopathy on ultrasound and radiography shows hyperemia, pathology of the adjacent tendon, possible erosions, and indistinct contours of enthesophytes. Enthesitis assessment in spondyloarthropathies is conducted using power Doppler (Kiris et al., 2006; Naredo et al., 2010).