Differential Diagnosis for Swelling of Gastrocnemius on X-ray with Acute Knee Pain

• Single Most Likely Diagnosis
  • Muscle strain or tear of the gastrocnemius: This is the most likely diagnosis given the swelling of the gastrocnemius muscle on X-ray, which is often associated with muscle injuries, particularly strains or tears. The acute knee pain could be referred pain from the injury site.
• Other Likely Diagnoses
  • Deep vein thrombosis (DVT): Although less common, DVT can cause swelling and pain in the calf, which might be mistaken for a muscle injury. The presence of acute knee pain could be coincidental or related to decreased mobility due to the DVT.
  • Baker's cyst: A fluid-filled swelling that causes a bulge and a feeling of tightness behind the knee, which could be related to the swelling seen on the X-ray and might cause referred pain to the knee.
  • Gastrocnemius tendinitis: Inflammation of the tendon connecting the gastrocnemius muscle to the bone, which could cause pain and swelling in the area and contribute to knee pain.
• Do Not Miss Diagnoses
  • Pulmonary embolism (if DVT is present): Although less directly related to the swelling of the gastrocnemius, if a DVT is suspected, it's crucial to consider the risk of a pulmonary embolism, which is life-threatening.
  • Compartment syndrome: A condition where pressure within the muscle compartments increases, potentially cutting off blood flow. It's a medical emergency that requires immediate attention.
• Rare Diagnoses
  • Soft tissue tumors (e.g., sarcomas): Although rare, tumors in the soft tissues around the knee could cause swelling and pain, mimicking more common conditions.
  • Infections (e.g., abscess or cellulitis): Infections in the soft tissues could cause swelling, redness, and pain, and while less common, they should be considered, especially if there are signs of infection or a compromised immune system.