Differential Diagnosis for Smacked 2nd Toe with Mild Swelling and Painful Ambulation

Single Most Likely Diagnosis

• Soft tissue injury (contusion or bruise): Given the history of trauma to the 2nd toe and the presence of mild swelling at the base of the metatarsophalangeal (MTP) joint without evidence of a fracture on foot X-ray, a soft tissue injury is the most plausible explanation. This type of injury can cause pain and swelling, especially with ambulation.

Other Likely Diagnoses

• Ligament sprain: The mechanism of injury could also result in a sprain of the ligaments surrounding the MTP joint, leading to pain and swelling.
• Turf toe: This is a specific type of injury to the ligaments around the big toe but can also occur in other toes, especially with hyperextension injuries. It could be considered given the location and mechanism of injury.
• Metatarsalgia: Although more commonly associated with pain in the ball of the foot, metatarsalgia could be a consideration if the pain is more diffuse and related to the way the foot is loading after the injury.

Do Not Miss Diagnoses

• Compartment syndrome: Although less likely, compartment syndrome is a serious condition that requires prompt diagnosis and treatment. It could occur after a significant trauma to the foot, leading to increased pressure within the compartments of the foot.
• Infection (e.g., cellulitis): If the skin was broken during the injury, there's a risk of infection. Early signs might include redness, swelling, and increased pain.
• Neurovascular injury: Damage to nerves or blood vessels could occur with significant trauma and might present with numbness, tingling, or coolness of the toe.

Rare Diagnoses

• Stress fracture: Although the X-ray did not show a fracture, stress fractures might not be visible on initial X-rays. If pain persists, especially with weight-bearing activities, a stress fracture could be considered.
• Gout or pseudogout: These conditions can cause sudden onset of pain and swelling in the toes, although they are less likely given the traumatic onset in this case.
• Osteochondritis dissecans: A condition where a piece of cartilage and a thin layer of the bone beneath it die due to inadequate blood supply, potentially caused by trauma. It's rare in the toes but could be a consideration with persistent pain.