USMLE Step 1 · MSK & Rheumatology

Achilles tendinitis vs Plantar fasciitis

How to tell Achilles tendinitis and Plantar fasciitis apart when a board question makes them look alike.

Fastest separator

Achilles pain is posterior tendon pain with plantarflexion; plantar fasciitis is plantar medial first-step heel pain.

Side by side

Achilles tendinitisPlantar fasciitis

Key clue

Achilles tendinitis causes posterior heel pain along the Achilles tendon, worse with running, jumping, or resisted plantarflexion.

Plantar fasciitis causes plantar medial heel pain, worst with first steps in the morning and tenderness at the medial calcaneal tubercle.

Mechanism

Overuse causes tendon degeneration and inflammation at or near Achilles insertion.

Microtears and degeneration of the plantar fascia origin cause start-up heel pain.

Labs and tests

Posterior tendon tenderness and pain with calf raise or resisted plantarflexion support Achilles tendinopathy.

Point tenderness at plantar fascia insertion and first-step pain support plantar fasciitis.

The trap

Both are heel pain, so pain location and first-step versus tendon-loading pattern separate them.

The repair move

For heel pain, localize in two steps: (1) where is the pain? Posterior heel along the Achilles tendon with tenderness on direct palpation and pain with plantarflexion against resistance equals Achilles tendinitis or tendinopathy (high-yield association with fluoroquinolone-induced tendinopathy and risk of complete rupture, especially in older patients on steroids; Thompson test to rule out complete rupture: squeezing the calf with the patient prone should plantarflex the foot absence of motion suggests rupture). (2) Inferior medial heel pain with the classic 'first step in the morning' pain that improves with walking and worsens again with prolonged standing equals plantar fasciitis (associated with obesity, prolonged standing, high-arched or flat feet; treat with stretching exercises, plantar fascia and Achilles stretches, orthotics, and NSAIDs; avoid corticosteroid injection because of plantar fascia rupture risk).

Try a free question

Core

A 38-year-old recreational runner has 6 weeks of progressive pain in the posterior aspect of the right heel and lower calf. Pain is worst at the start of activity, improves with continued running, and recurs after rest. Exam shows tenderness 4 cm proximal to the calcaneal insertion of the Achilles tendon. Resisted plantarflexion reproduces pain. Which diagnosis is most likely?

Show answer and explanation

Answer: A. Achilles tendinopathy/tendinitis. Achilles tendinopathy presents with posterior heel and calf pain at or just proximal to the calcaneal insertion, worse with activity onset, improves with continued movement, and recurs after rest; treatment is eccentric calf exercises, NSAIDs, and activity modification.

Why the other choices are tempting

B. Plantar fasciitis pain is on the PLANTAR surface of the medial heel, not the posterior tendon.
C. Achilles tendon rupture presents with sudden severe pain, palpable defect, positive Thompson test (absent plantarflexion when squeezing the calf), and inability to plantarflex.
D. Calcaneal stress fracture has pain with weight-bearing and abnormal MRI/bone scan.
E. Retrocalcaneal bursitis affects the bursa between the Achilles tendon and calcaneus, with pain at the posterior heel directly.

Flashcards

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What location supports Achilles tendinitis?

Posterior heel pain along the Achilles tendon supports Achilles tendinitis.

What timing supports plantar fasciitis?

Pain with first morning steps supports plantar fasciitis.

Quick answers

What is the fastest way to tell Achilles tendinitis from Plantar fasciitis?