Differential Diagnosis for Bilateral Thigh Pain

The patient's symptoms of bilateral thigh pain, a popping sensation while running, followed by nausea, dizziness, swelling, bruising, and difficulty squatting and standing up suggest a significant injury. Here are the differential diagnoses categorized for clarity:

• Single Most Likely Diagnosis

  • Bilateral Quadriceps Tendon Rupture: This condition is suggested by the sudden onset of pain, the audible pop, and the inability to stand up from a squatting position, which indicates a significant loss of quadriceps function. The bilateral nature and the acute presentation make this a highly plausible diagnosis.

• Other Likely Diagnoses

  • Bilateral Hamstring Strains: Although less likely than quadriceps tendon rupture given the specific symptoms, severe hamstring strains could cause significant pain and dysfunction, especially if they involve a substantial portion of the muscle.
  • Bilateral Femur Fractures: Stress fractures or acute fractures could present with thigh pain and difficulty bearing weight, though the bilateral and simultaneous onset would be unusual.
  • Compartment Syndrome: This is a condition that could arise from severe muscle injury, leading to increased pressure within the muscle compartments, which could cause pain, swelling, and potentially long-term damage if not promptly treated.

• Do Not Miss Diagnoses

  • Osteonecrosis: Although less common, osteonecrosis (avascular necrosis) of the femur could present with thigh pain and should be considered, especially if the patient has risk factors such as long-term steroid use or excessive alcohol consumption.
  • Deep Vein Thrombosis (DVT): While DVT typically presents with unilateral symptoms, in rare cases, it could be bilateral. The symptoms of swelling and pain could overlap, making it crucial not to miss this potentially life-threatening condition.
  • Neoplastic Processes: Rarely, metastatic disease or primary bone tumors could cause bilateral thigh pain, and while unlikely, missing such a diagnosis could have severe consequences.

• Rare Diagnoses

  • Bilateral Stress Fractures of the Pelvis: These could present with pain in the thigh area, especially if the fractures involve the pubic rami or the sacrum.
  • Muscular Dystrophy: Certain types of muscular dystrophy could lead to muscle weakness and pain, though the acute presentation in this case makes it less likely.
  • Inflammatory Myopathies: Conditions like polymyositis or dermatomyositis could cause muscle weakness and pain, but the bilateral thigh pain and acute onset described would be an unusual presentation.

Each of these diagnoses should be considered in the context of the patient's full medical history, physical examination, and appropriate diagnostic tests to determine the most accurate diagnosis and guide treatment.