Differential Diagnosis for Non-Contact Twisting Knee Injury with Pain Radiating Up Thigh

• Single Most Likely Diagnosis
  • Anterior Cruciate Ligament (ACL) Tear: This is the most common injury from a non-contact twisting mechanism, especially in sports that involve sudden changes of direction. The ACL is crucial for knee stability, and its rupture can cause significant pain and instability.
• Other Likely Diagnoses
  • Meniscal Tear: The menisci are cartilage structures in the knee that can be damaged by twisting injuries. Symptoms include pain, swelling, and sometimes locking of the knee.
  • Medial Collateral Ligament (MCL) Sprain: Although more commonly associated with valgus stress, an MCL sprain can occur from a twisting injury, especially if there's a component of valgus stress involved.
  • Osteochondral Defect: This refers to a condition where a piece of cartilage and bone in the knee joint is damaged. It can cause pain and locking symptoms.
• Do Not Miss Diagnoses
  • Popliteal Artery Injury: Although rare, a severe twisting injury could potentially damage the popliteal artery, leading to acute limb ischemia, which is a medical emergency.
  • Peroneal Nerve Injury: The peroneal nerve wraps around the lateral aspect of the knee and can be injured in severe twisting mechanisms, leading to foot drop or other neurological deficits.
• Rare Diagnoses
  • Spontaneous Osteonecrosis of the Knee (SONK): This is a rare condition where a portion of the knee bone dies due to lack of blood supply. It can cause sudden onset of knee pain.
  • Stress Fracture: While more common in the lower leg or foot, stress fractures can occur in the knee area, especially with repetitive stress rather than a single twisting injury. However, they should be considered in the differential, especially in athletes.