Differential Diagnosis for Acute Right Foot Pain with Flexion

Single Most Likely Diagnosis

• Plantar fasciitis: This condition is the most common cause of heel pain and can be exacerbated by flexion of the foot. It is characterized by inflammation of the plantar fascia, leading to pain and stiffness, especially after periods of rest or with activities that involve flexion.

Other Likely Diagnoses

• Achilles tendonitis: Inflammation of the Achilles tendon can cause pain in the back of the ankle, which may worsen with flexion of the foot. This condition is common in runners and individuals who participate in sports that involve repetitive ankle movements.
• Morton's neuroma: This condition involves thickening of the tissue around a nerve in the foot, leading to pain, usually between the third and fourth toes. Flexion of the foot can exacerbate the pain.
• Stress fracture: A small crack in one of the bones in the foot can cause acute pain, especially with weight-bearing activities or flexion of the foot. Stress fractures are common in athletes or individuals with sudden increases in physical activity.

Do Not Miss Diagnoses

• Compartment syndrome: Although less common, compartment syndrome is a serious condition that requires immediate medical attention. It involves increased pressure within a muscle compartment, leading to pain, especially with flexion, and can result in permanent damage if not treated promptly.
• Deep vein thrombosis (DVT): While DVT typically presents with swelling and pain in the calf, in rare cases, it can cause foot pain. Given the potential for severe complications like pulmonary embolism, DVT should not be missed.
• Infection (e.g., cellulitis, abscess): Infections in the foot can cause severe pain, redness, and swelling. They require prompt antibiotic treatment to prevent serious complications.

Rare Diagnoses

• Gout: An inflammatory arthritis characterized by sudden, severe attacks of pain, swelling, redness, and tenderness, often in the big toe. While not typically associated with flexion, it can cause acute foot pain.
• Pseudogout (calcium pyrophosphate deposition disease): Similar to gout, pseudogout causes sudden, severe joint pain, but it is less common in the foot and more often affects the knee.
• Tarsal tunnel syndrome: Compression of the posterior tibial nerve as it travels through the tarsal tunnel on the inner side of the ankle can cause pain, numbness, and tingling in the foot, which may worsen with flexion.