Differential Diagnosis for Posterior Heel Slightly Lateral Pain

Single Most Likely Diagnosis

• Plantar Fasciitis: Although plantar fasciitis typically presents with pain on the underside of the heel, it can sometimes radiate or be felt on the sides, including the posterior lateral aspect, especially if the fascia is inflamed and irritated.

Other Likely Diagnoses

• Achilles Tendinitis: This condition causes pain in the back of the heel due to inflammation of the Achilles tendon. The pain can be slightly lateral if the tendonitis affects the tendon where it attaches to the calcaneus or if there is a tendinosis that is more pronounced on one side.
• Retrocalcaneal Bursitis: Inflammation of the bursa that separates the Achilles tendon from the heel bone can cause pain in the posterior heel area, potentially feeling slightly lateral depending on the bursa's exact location and extent of inflammation.
• Peroneal Tendinitis: The peroneal tendons run down the lateral side of the ankle and behind the lateral malleolus. Tendinitis in these tendons can cause pain that might be felt in the posterior lateral heel area, especially if the tendons are irritated as they pass behind the fibula and near the heel.

Do Not Miss Diagnoses

• Fracture of the Calcaneus: A fracture in the heel bone can cause severe pain in the heel area, including the posterior lateral aspect. This is a critical diagnosis not to miss due to the potential for long-term disability if not properly treated.
• Tumor: Although rare, a tumor in the heel area, such as a calcaneal osteoid osteoma, can cause persistent pain that might be localized to the posterior lateral heel.
• Infection (Osteomyelitis or Septic Arthritis): Infections in the bone or joint of the heel can cause severe pain and have serious consequences if not promptly treated.

Rare Diagnoses

• Haglund's Deformity: A bony enlargement at the back of the heel bone can cause pain in the posterior heel area, especially if it irritates the Achilles tendon or the bursa. It might feel slightly lateral depending on the deformity's size and location.
• Tarsal Tunnel Syndrome: Compression of the posterior tibial nerve as it travels through the tarsal tunnel can cause pain, numbness, and tingling in the foot. While less common, it could potentially cause pain felt in the posterior lateral heel area if the nerve compression affects the smaller branches of the nerve.