Sonography of chronic Achilles tendinopathy: a case-control study.

Purpose: To describe the sonographic appearance of Achilles tendon in normal subjects and patients with chronic Achilles tendinopathy with the aim of establishing diagnostic sonographic criteria for Achilles tendinopathy.

Methods: A prospective, cross-sectional, case-control sonographic study of the Achilles tendon was undertaken. Thirty tendons in 21 patients and 100 tendons in 50 control subjects were selected. Sonographic assessment included tendon thickness, echogenicity, fibrillar pattern, and presence of calcifications. Power Doppler imaging was used to assess tendon vascularity. Paratendinous structures and plantar fascia were also examined.

Results: Tendinopathic tendons were larger than normal tendons in both cross-sectional area and antero-posterior diameter. Hypoechoic areas within the tendon were more commonly seen in patients. Disruption of fibrillar pattern, increase in tendon vascularity, increased Kager's fat pad echogenicity, and paratenon thickening were solely seen in patients. Fluid in the retrocalcaneal bursa and calcaneal bony abnormalities were seen in both groups without a significant difference.

Conclusion: Achilles tendinopathy results in enlargement, particularly of the mid- and distal portions of the tendon, disruption of fibrillar pattern, and increase in tendon vascularity. Additional signs are increased Kager's fat pad echogenicity and paratenon thickening. Tendon calcification, changes in retrocalcaneal bursae, and calcaneal contour are not specific for Achilles tendinopathy.