Location and Topography
The calcaneal (Achilles) tendon serves as a key surface landmark of the posterior ankle region (Regio talocruralis posterior). Vertical grooves lie on either side of the tendon, and the lateral boundaries of the region correspond to the borders of the tendon. The lateral and medial malleoli also serve as external landmarks.
- Skin: Thicker than on the anterior aspect of the leg. Forms transverse skin folds during plantarflexion of the foot.
- Bursae: The gastrocnemius tendon bursa (bursa subtendinea m. gastrocnemii) lies deep to the tendon, while the subcutaneous calcaneal bursa (bursa subcutanea calcanea) lies superficial to it.
- Blood supply: Calcaneal branches (rr. calcanei) arising from both medial and lateral sides supply the heel region, forming the calcaneal network (rete calcaneum). In the lateral retromalleolar region, calcaneal branches of the fibular [peroneal] artery (rami calcanei a. fibularis [peronea] also contribute.
Neurology: The Achilles Reflex
The Achilles reflex (ankle jerk reflex) is elicited by striking the Achilles tendon with a reflex hammer.
- Testing technique: The patient's leg is flexed at the knee, and the foot is held in a neutral position midway between dorsiflexion and plantarflexion.
- Facilitation: The examiner may slightly stretch the Achilles tendon by applying gentle passive dorsiflexion to the foot. If lower extremity deep tendon reflexes are absent or diminished, the Jendrassik maneuver is used: the patient hooks the fingers of both hands together and pulls them apart forcefully.
- Response: Plantarflexion of the foot.
- Effector muscles: Contraction of the gastrocnemius and soleus muscles.
- Reflex arc level: Spinal cord segments S₁–S₃ (commonly referenced in clinical neurology as S₁–S₂).
- Clinical significance: Diminution or absence of the reflex indicates a lesion of the peripheral reflex arc, including the anterior horn cells of the spinal cord. Hyperreflexia (exaggerated reflex) indicates an upper motor neuron lesion affecting the corticospinal (pyramidal) tract above the level of the reflex arc.
Clinical Significance in Rheumatology
The Achilles tendon is a classic site for enthesopathies.
- Enthesitis/Enthesopathy: Pathology at the insertion sites of tendons, ligaments, or joint capsules into bone. It manifests as spontaneous pain or localized tenderness on palpation and is a hallmark feature of the spondyloarthropathies.
- Psoriatic arthritis: The Achilles tendon insertion is included bilaterally in anatomical scoring systems such as the Leeds Enthesitis Index (LEI). This index assesses enthesitis severity by simply summing the presence of tenderness at designated sites.
- Idiopathic gout: Tendons, including the Achilles tendon, can be a site for tophi deposition.