Differential Diagnosis for Left Achilles Tendon Tenderness and Swelling

• Single Most Likely Diagnosis
  • Achilles Tendinitis: This is the most common condition affecting the Achilles tendon, characterized by inflammation of the tendon, leading to pain, tenderness, and sometimes swelling. The symptoms described, such as tenderness and a feeling of difference compared to the other leg, are classic for Achilles tendinitis, which can be caused by overuse, sudden increase in exercise, or poor footwear.
• Other Likely Diagnoses
  • Achilles Tendinosis: Similar to tendinitis but involves chronic degeneration of the tendon without significant inflammation. It presents with pain and stiffness, especially after periods of rest, and can feel like the tendon is "different" or not as resilient as the unaffected side.
  • Achilles Bursitis: Inflammation of the bursae (fluid-filled sacs) that cushion the Achilles tendon can cause pain, swelling, and tenderness in the area. This condition can result from repetitive ankle motion, direct blows to the area, or inflammatory diseases like rheumatoid arthritis.
  • Overuse Injury: General overuse or repetitive strain on the Achilles tendon and surrounding muscles can lead to pain, stiffness, and a feeling of abnormality in the affected leg compared to the unaffected one.
• Do Not Miss Diagnoses
  • Rupture of the Achilles Tendon: Although less likely if the patient is still able to walk and bear weight, a partial or complete rupture of the Achilles tendon is a critical diagnosis not to miss. It typically presents with a sudden, severe pain in the back of the ankle, sometimes accompanied by a "pop" sound, and significant weakness or inability to stand on toes.
  • Deep Vein Thrombosis (DVT): While less common in the context of Achilles tendon symptoms, DVT can cause swelling, pain, and tenderness in the leg. It's a potentially life-threatening condition if the clot dislodges and travels to the lungs (pulmonary embolism).
• Rare Diagnoses
  • Infectious Tendinitis: Bacterial or fungal infections of the tendon, which can occur, especially in immunocompromised patients or after a puncture wound. Symptoms include increased redness, warmth, swelling, and sometimes pus.
  • Tumor or Cyst: Rarely, a soft tissue tumor (like a lipoma or sarcoma) or a cyst (such as a ganglion cyst) can develop near the Achilles tendon, causing a palpable mass, pain, and a feeling of the tendon being "different."
  • Seronegative Spondyloarthropathies: Conditions like ankylosing spondylitis, psoriatic arthritis, reactive arthritis, and enteropathic arthritis can cause Achilles tendinitis among other systemic symptoms. These are less common but important to consider in the differential diagnosis, especially if other systemic symptoms are present.