Differential Diagnosis for the Patient's Condition

The patient's presentation of a twisted knee with a rotation and click, followed by difficulty in ambulation and pain on extension, suggests a mechanical issue with the knee. The absence of erythema, warmth, or edema makes an infectious or inflammatory cause less likely. Here is a categorized differential diagnosis:

• Single Most Likely Diagnosis

  • Meniscal Tear: The mechanism of injury (twisting) and the symptoms (pain on extension, limited range of motion, and difficulty in ambulation) are classic for a meniscal tear. The "click" felt during the injury could be indicative of the meniscus tearing.

• Other Likely Diagnoses

  • Ligamentous Sprain: Although the knee is not edematous, a sprain, especially to the medial or lateral collateral ligaments, could occur from a twisting injury and cause pain and limited mobility.
  • Patellofemoral Pain Syndrome: This condition could be considered if the pain is more anterior and related to the patella, especially if the patient has a history of similar pain or if the examination reveals patellar maltracking or tenderness.

• Do Not Miss Diagnoses

  • Fracture (e.g., Tibial Plateau): Although the knee is not edematous or warm, a fracture could still be present, especially if the mechanism of injury involved significant force. Missing a fracture could lead to serious complications, including malunion or nonunion.
  • Septic Arthritis: Even though the knee is not erythematous or warm, septic arthritis is a medical emergency that must be considered, especially if the patient has a fever or risk factors for infection (e.g., recent joint injection, immunocompromised state).

• Rare Diagnoses

  • Osteochondritis Dissecans: This condition involves a piece of cartilage and bone becoming detached from the surrounding bone, often due to trauma. It could present with locking or catching sensations and pain.
  • Discoid Meniscus: A rare congenital condition where the meniscus is thicker and more prone to tearing. Symptoms could mimic those of a meniscal tear but might have a more chronic presentation.