Differential Diagnosis for Leg Pain

The patient presents with leg pain on the anterior thigh radiating to the knee and leg. Here's a differential diagnosis organized into categories:

• Single Most Likely Diagnosis

  • Meralgia Paresthetica: This condition is characterized by numbness, tingling, and burning pain in the outer part of the thigh. It occurs when the lateral femoral cutaneous nerve, which supplies sensation to the skin surface of the thigh, is compressed. The symptoms can radiate down to the knee and are often exacerbated by standing or walking.

• Other Likely Diagnoses

  • Femoral Neuropathy: This involves damage to the femoral nerve, which can cause pain, weakness, and numbness in the front of the thigh and sometimes down to the knee. Causes can include compression, trauma, or diseases affecting the nerve.
  • Quadriceps Tendinopathy: Inflammation or degeneration of the quadriceps tendon can cause pain in the front of the thigh, which may radiate down towards the knee, especially with activities like jumping, running, or even simple movements like climbing stairs.
  • Osteoarthritis of the Knee: While primarily affecting the knee joint, osteoarthritis can cause referred pain up into the thigh. The pain is usually worse with weight-bearing activities and can be accompanied by stiffness and limited mobility.

• Do Not Miss Diagnoses

  • Deep Vein Thrombosis (DVT): Although DVT typically presents with swelling, redness, and warmth of the affected limb, it can sometimes cause pain without these other symptoms. It's crucial to consider DVT due to its potential for leading to a life-threatening pulmonary embolism if not treated promptly.
  • Aortic Aneurysm or Aortic Dissection: These are emergencies that can present with severe back or abdominal pain but can also radiate to the thighs. A high index of suspicion is required, especially in patients with risk factors such as hypertension or a history of vascular disease.
  • Spinal Stenosis: This condition involves narrowing of the spinal canal, which can compress nerves and cause pain, numbness, or weakness in the legs. The pain often worsens with standing or walking and improves with sitting or leaning forward.

• Rare Diagnoses

  • Peripheral Artery Disease (PAD): While more commonly associated with claudication (pain in the legs or buttocks during exercise), PAD can cause pain at rest if the disease is severe. It's less likely but should be considered, especially in smokers or those with diabetes.
  • Neoplastic Processes: Tumors, either primary in the bone or soft tissues of the thigh or metastatic, can cause pain. These are less common but important to rule out, especially with persistent or worsening symptoms.
  • Inflammatory Myopathies: Conditions like polymyositis or dermatomyositis can cause muscle weakness and pain, which might be perceived as radiating pain in the thigh and knee. These are relatively rare and usually accompanied by other systemic symptoms.