To determine if the viscoelastic properties of Achilles tendon assessed by real-time sharewave elastography (SWE) are modified in tendinopathy and provide informations for subsequent applications of this technique.

Twenty-six abnormal tendons (16 unilateral and 5 bilateral tendinopathy) from 21 patients with Achilles tendinopathy and 176 normal tendons (from 16 patients and 80 healthy volunteers) were prospectively included and compared. Mean sharewave velocity (Vmean) was measured on axial and sagittal SWE images at two degrees of passive ankle flexion (position 1: complete plantar flexion? and position 2: 0 degree flexion). Tendon maximum anteroposterior and lateral diameters, cross sectional area and the presence of tears were also noted.

In position 1, the abnormal tendons Vmean was significantly lower than for contralateral normal tendons on sagittal (Δ=1.23m/s, P=0.004) and axial elastograms (Δ=0.68 m/s, P=0.03)? and significantly lower than for normal tendons only on axial images (Δ=0.49 m/s, P=0.01). In position 2 and on axial elastograms, the abnormal tendons Vmean was 1.14 m/s lower than for contralateral normal tendons however without reaching statistical significance (P=0.07). In position 2, the abnormal tendons Vmean was significantly lower than for normal tendons on sagittal (Δ=1.26 m/s, P<0.001) and axial elastograms (Δ=0.52 m/s, P=0.05). In tendon with complete tears Vmean was significantly lower than for normal tendons on both sagittal and axial images and in both positions (P<0.001). All tears (n=4) appeared as signal void areas.

Abnormal Achilles tendons have lower Vmean and are therefore softer than normal tendons. There is no SWE signal into tendon tears. Tendon softening, assessed by realtime SWE, is a new helpful tool in the evaluation of Achilles tendinopathy. SWE may also provide quantitative parameters to assess the severity of tendinopathy to monitor the effect of therapeutics.