Differential Diagnosis for Suprapatellar Joint Effusion

• Single most likely diagnosis
  • Osteoarthritis: This is a common condition that affects the joints, including the knee, leading to inflammation and effusion. The suprapatellar joint is often involved in osteoarthritis of the knee.
• Other Likely diagnoses
  • Meniscal tear: Tears in the meniscus, which is the cartilage between the bones in the knee, can lead to joint effusion, including in the suprapatellar region.
  • Ligament sprain: Sprains to the ligaments around the knee can cause inflammation and effusion.
  • Patellofemoral pain syndrome: This condition, characterized by pain around or behind the patella, can also lead to joint effusion.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Septic arthritis: Although less common, septic arthritis is a serious condition that requires prompt treatment. It can cause significant joint effusion and has the potential for severe consequences if not addressed.
  • Hemarthrosis: Bleeding into the joint space, which could be due to trauma or a bleeding disorder, is a critical condition that needs immediate attention.
• Rare diagnoses
  • Rheumatoid arthritis: While not as common as osteoarthritis, rheumatoid arthritis can also affect the knee and cause suprapatellar joint effusion.
  • Gout or pseudogout: These conditions, characterized by the deposition of crystals within the joints, can lead to acute inflammatory reactions and effusion.
  • Synovial chondromatosis: A rare condition where cartilage grows in the synovium, leading to joint effusion and other symptoms.
  • Pigmented villonodular synovitis (PVNS): A rare disease that causes the synovium to thicken and overgrow, leading to joint effusion and other complications.