Differential Diagnosis for Achilles Tendon Pain
Primary Diagnostic Considerations
The differential diagnosis for Achilles tendon pain includes insertional Achilles tendinopathy, non-insertional Achilles tendinopathy, retrocalcaneal bursitis (often associated with Haglund's deformity), Achilles tendon rupture (partial or complete), and neurologic heel pain from nerve entrapment. 1
Insertional Achilles Tendinopathy
- Presentation: Insidious onset of chronic posterior heel pain and swelling at the tendon insertion site, with pain aggravated by increased activity and pressure from shoes 1
- Key distinguishing feature: Pain relief occurs when walking barefoot, opposite to most other heel conditions 1
- Physical examination findings: Prominence appreciated medially and laterally to the Achilles tendon insertion, with central or global tenderness present 1
- Imaging: Radiographs often demonstrate spurring or erosion at the Achilles tendon insertion 1
Non-Insertional Achilles Tendinopathy
- Presentation: Most patients experience posterior heel pain proximal to the tendon insertion, typically 2-6 cm above the calcaneal attachment 1
- Physical examination findings: Thickening of the tendon with tender, palpable nodules in the mid-substance of the tendon 1
- Patient demographics: Common among adult runners with higher incidence as age increases 1
- Pathophysiology: Failed healing response progressing through reactive tendinopathy, tendon disrepair, and degenerative tendinopathy with collagen disorganization and neovascularization 2, 3
Retrocalcaneal Bursitis with Haglund's Deformity
- Patient demographics: Most common in women aged 20-30 years, though can occur in both sexes at any age 1
- Presentation: Acute pain and inflammation aggravated by pressure from shoes, with relief when walking barefoot 1
- Physical examination findings: Tenderness lateral to the Achilles tendon, usually associated with a posterior lateral prominence 1
- Imaging: The posterior lateral prominence is commonly visible on radiographs 1
Achilles Tendon Rupture
- Clinical diagnosis: Perform two or more of the following tests to establish diagnosis: positive Thompson test (calf squeeze test showing absent plantar flexion), decreased ankle plantar flexion strength, presence of palpable gap or defect, and increased passive ankle dorsiflexion with gentle manipulation 1
- Presentation: Typically acute onset with sudden pain, often described as feeling like being "kicked in the back of the leg" 1
- Important caveat: Routine MRI, ultrasonography, and radiography are not necessary to confirm the diagnosis when clinical examination is conclusive 1
Neurologic Heel Pain
- Etiology: Results from irritation or entrapment of nerves innervating the heel, or from more proximal nerve impingement syndromes causing referred pain 1
- Management approach: Subspecialist referral for evaluation and diagnostic testing should be considered when neurologic heel pain is suspected 1
- Diagnostic studies: May include electromyography, nerve conduction velocity studies, and MRI 1
- Referral patterns: Podiatric foot and ankle surgeons may manage local conditions, while referral to spine specialists is required for problems originating in the lumbar area 1
Key Diagnostic Pitfalls to Avoid
- Do not rely solely on imaging: Clinical examination with morning stiffness, pain on palpation, and detection of Achilles tendon thickening are the most useful diagnostic tools 2
- Distinguish location carefully: Insertional versus non-insertional tendinopathy requires different treatment approaches, particularly regarding corticosteroid injection safety 1, 4
- Consider biomechanical factors: Pay special attention to anatomic deformities such as forefoot and heel varus, excessive pes planus, or foot pronation, as these contribute to development and persistence of symptoms 1, 4
- Assess for systemic factors: Risk factors include female sex, higher body mass index, prior tendinopathy, fluoroquinolone antibiotic use, oral contraceptives, and hormone replacement therapy 2