Differential Diagnosis for Posterior Knee Pain

Single Most Likely Diagnosis

• Baker's Cyst: This is a fluid-filled swelling that causes a bulge and a feeling of tightness behind the knee. It is the most common cause of posterior knee pain and is often associated with knee arthritis or a meniscal tear.

Other Likely Diagnoses

• Meniscal Tear: Tears in the cartilage of the knee joint can cause pain in the posterior aspect of the knee, especially if the tear is in the posterior horn of the meniscus.
• Gastrocnemius or Popliteus Tendinitis: Inflammation of the tendons of the gastrocnemius or popliteus muscles can cause pain in the posterior knee.
• Posterior Knee Ligament Sprain: Sprains to the ligaments in the posterior knee, such as the posterior cruciate ligament (PCL), can cause pain and instability.

Do Not Miss Diagnoses

• Deep Vein Thrombosis (DVT): Although less common, DVT can cause posterior knee pain and swelling, and is a potentially life-threatening condition if not treated promptly.
• Popliteal Artery Aneurysm: An aneurysm of the popliteal artery can cause posterior knee pain and is a serious condition that requires urgent medical attention.
• Tumor: Although rare, tumors such as osteosarcoma or soft tissue sarcomas can cause posterior knee pain and should not be missed.

Rare Diagnoses

• Cystic Adventitial Disease: A rare condition where a cyst forms in the wall of the popliteal artery, causing posterior knee pain and claudication.
• Popliteal Cystic Hygroma: A rare congenital condition where a cyst forms in the posterior knee, causing pain and swelling.
• Ganglion Cyst: A rare condition where a cyst forms in the posterior knee, causing pain and swelling.