Achilles Tendon Injury

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Diagnosis Definition

The Achilles tendon is the strongest and thickest tendon in the body, connecting gastrocnemius and soleus calf muscles to the calcaneus
Predisposing conditions include rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus, and gout
Injuries include tendinitis, partial tear, complete tear, and chronic tear; generally during athletic activity

Imaging Findings

Sequences include sagittal T1 and STIR, axial PD and T2 FS, and coronal PD and T2 FS
The Achilles tendon is tapered, with uniformly dark signal on all sequences; in cross section, it has a C-shape that is concave toward the tibia, but becomes convex and thickened with tendinopathy or tears
Partial tears are seen as thickening of the tendon with longitudinal bands of increased T1 and T2 signal
In complete tears, MR shows tendon discontinuities with high T2 signal; tendon-end retraction may be seen
With chronic tears, retracted tendon edges, and atrophy of tendon fibers and muscles are seen

Pearls

Because the Achilles tendon does not have a tendon sheath, tenosynovitis and fluid around the tendon are not seen; however, soft tissue edema in the soft tissues surrounding the tendon may be present after an acute tear
Average Achilles tendon thickness is 6 mm
Most tears occur 2-6 cm from insertion

References

Schweitzer M, Karasick D. MR imaging of disorders of the Achilles tendon. American Journal of Roentgenology 2000; Vol. 175, Pp. 613-625.

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