Differential Diagnosis for Left Tibia Dent and Pain without Trauma in a Runner

• Single most likely diagnosis:
  • Medial tibial stress syndrome (MTSS): Also known as shin splints, this condition is common in runners and athletes who participate in sports that involve running. The pain is typically located on the medial (inner) aspect of the tibia and can be exacerbated by activity. The absence of trauma, swelling, or bruising, along with the patient's running history, makes MTSS a strong candidate for the diagnosis.
• Other Likely diagnoses:
  • Stress fracture: A small crack in the bone, often caused by repetitive stress or overuse. Runners are at risk, and the symptoms can include pain that worsens with activity. While stress fractures can occur without significant trauma, they might not always present with a noticeable "dent."
  • Periostitis: Inflammation of the periosteum, a layer of connective tissue that surrounds bone. This condition can cause pain and tenderness, especially in areas subjected to repetitive stress like the tibia in runners.
• Do Not Miss diagnoses:
  • Osteosarcoma: A type of bone cancer that can present with pain and swelling, although swelling might not always be present early on. It's crucial to consider this diagnosis, especially if the pain is persistent and worsening, despite the low likelihood.
  • Infection (osteomyelitis): An infection of the bone that can cause pain, fever, and sometimes swelling. While less common without a clear source of infection or trauma, it's a critical diagnosis not to miss due to its potential severity.
• Rare diagnoses:
  • Bone cysts or tumors (e.g., osteoid osteoma): These are benign growths that can cause pain, often worse at night. They might not be directly related to running but could be considered in the differential diagnosis if other causes are ruled out.
  • Chronic exertional compartment syndrome: This condition involves increased pressure within the muscle compartments, leading to pain during exercise. It's less common but should be considered in athletes with exercise-induced leg pain.