Differential Diagnosis for Knee Pain with No Trauma
Single Most Likely Diagnosis
- Osteoarthritis: This is a common condition that can cause knee pain, swelling, and limited mobility, including flexion. The absence of trauma and the presence of swelling make osteoarthritis a plausible diagnosis.
Other Likely Diagnoses
- Meniscal Cyst or Meniscal Tear: Although the question specifies no trauma, minor, unnoticed injuries can occur, and meniscal issues can cause swelling and limited knee flexion.
- Ligament Sprain: Similar to meniscal tears, ligament sprains can occur without significant trauma and lead to knee pain, swelling, and limited mobility.
- Bursitis: Inflammation of the bursae around the knee can cause pain, swelling, and limited movement, including flexion.
- Tendinitis: Inflammation of the tendons around the knee, such as the patellar tendon, can cause pain and limited mobility.
Do Not Miss Diagnoses
- Septic Arthritis: Although less likely, this is a serious condition that requires prompt treatment. Knee pain, swelling, and limited mobility can be symptoms of septic arthritis, which is an infection within the joint.
- Deep Vein Thrombosis (DVT): DVT can cause swelling and pain in the leg, including the knee area, and is a potentially life-threatening condition if not treated promptly.
- Osteonecrosis: This condition, also known as avascular necrosis, can cause knee pain and limited mobility due to the death of bone tissue, often due to inadequate blood supply.
Rare Diagnoses
- Hemophilia: In patients with hemophilia, even minor injuries or no trauma at all can lead to bleeding into the joints (hemarthrosis), causing pain, swelling, and limited mobility.
- Rheumatoid Arthritis: Although more commonly associated with multiple joint involvement, rheumatoid arthritis can present with knee pain, swelling, and limited flexion in one knee.
- Tumor or Cyst: Rarely, a tumor or cyst within or around the knee can cause pain, swelling, and limited mobility. Examples include synovial sarcoma or a ganglion cyst.