Differential Diagnosis for Knee Pain with Valgus Stress
Single Most Likely Diagnosis
- Medial Collateral Ligament (MCL) Sprain: This is the most likely diagnosis because the MCL is the primary stabilizer against valgus stress. A sprain to this ligament would cause pain, especially with valgus stress.
Other Likely Diagnoses
- Medial Meniscus Tear: The medial meniscus can be injured with valgus stress, leading to pain and potentially locking or catching sensations in the knee.
- Osteoarthritis: Valgus deformity and stress can exacerbate osteoarthritis, particularly in the medial compartment of the knee, leading to pain.
- Ligamentous Laxity or Instability: Generalized ligamentous laxity or specific instability patterns can lead to knee pain with valgus stress due to abnormal movement patterns.
Do Not Miss Diagnoses
- Fracture (e.g., Tibial Plateau Fracture): Although less common, a fracture could present with pain upon valgus stress and must be ruled out to avoid missing a potentially serious condition.
- Septic Arthritis: This is an infection within the joint that can cause severe pain, swelling, and warmth. It's a medical emergency and must be considered, especially if there's a history of fever, recent travel, or immune compromise.
- Osteonecrosis: Avascular necrosis of the femoral condyle could present with knee pain that worsens with weight-bearing activities and valgus stress.
Rare Diagnoses
- Pellegrini-Stieda Syndrome: This is a rare condition characterized by ossification of the MCL, which can cause chronic knee pain and stiffness.
- Tumors (e.g., Osteoid Osteoma, Osteosarcoma): Although rare, bone tumors can cause knee pain that may worsen with activity, including valgus stress.
- Infection of the MCL or Bursae: Infections in these areas are uncommon but can cause pain, swelling, and warmth, especially with valgus stress.