Differential Diagnosis for Unexplained Knee Effusion
- Single most likely diagnosis
- Osteoarthritis: This is the most common cause of knee effusion, especially in older adults. The wear and tear of the joint can lead to inflammation and fluid accumulation.
- Other Likely diagnoses
- Meniscal tear: A tear in the meniscus, which is the cartilage that cushions the joint, can cause knee effusion due to the resulting inflammation.
- Ligament sprain: A sprain in one of the ligaments surrounding the knee can lead to effusion as the body responds to the injury.
- Patellofemoral pain syndrome: This condition, characterized by pain around the kneecap, can sometimes cause effusion due to inflammation of the soft tissues.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Septic arthritis: Although less common, this condition is a medical emergency. Bacterial infection of the joint can lead to severe damage if not promptly treated.
- Hemarthrosis (bleeding into the joint): This could be due to trauma, bleeding disorders, or anticoagulant therapy. It's crucial to identify and manage the underlying cause to prevent further complications.
- Rare diagnoses
- Rheumatoid arthritis: An autoimmune disease that can cause inflammation and effusion in the knee, though it typically presents with multiple joint involvement.
- Gout or pseudogout: These are forms of arthritis that can cause sudden, severe joint pain and effusion, often with crystal deposition in the joint.
- Osteonecrosis: The death of bone tissue due to a lack of blood supply can lead to knee effusion among other symptoms.
- Neuropathic arthropathy: A condition characterized by progressive degeneration of a joint due to nerve damage, which can result in effusion.