Differential Diagnosis for Left Knee Pain
The patient presents with a one-month history of generalized left knee pain, mostly inside the knee, with initial swelling on the left upper side of the knee and no preceding trauma or injury. An x-ray shows left knee joint effusion with mild degenerative changes and an oval-shaped loose body in the proximal tibial metadiaphysis. Based on these findings, the differential diagnosis can be categorized as follows:
- Single Most Likely Diagnosis
- Osteochondritis Dissecans (OCD): This condition is characterized by a loose fragment of cartilage and bone within the joint, which can cause pain, swelling, and locking of the joint. The presence of an oval-shaped loose body in the proximal tibial metadiaphysis on the x-ray supports this diagnosis.
- Other Likely Diagnoses
- Meniscal Tear: A tear in the meniscus, which is the cartilage that cushions the joint, can cause pain, swelling, and locking of the knee. The location of the pain inside the knee and the presence of joint effusion on the x-ray make this a possible diagnosis.
- Synovial Chondromatosis: This condition is characterized by the growth of cartilage in the synovial membrane of the joint, which can cause joint effusion, pain, and swelling. The presence of a loose body on the x-ray and the absence of trauma or injury make this a possible diagnosis.
- Do Not Miss Diagnoses
- Septic Arthritis: This is a serious infection of the joint that requires prompt treatment. Although the patient does not have a history of trauma or injury, septic arthritis can occur without a clear source of infection. The presence of joint effusion and pain make this a diagnosis that should not be missed.
- Tumor (e.g., Osteosarcoma, Chondrosarcoma): Although rare, a tumor in the knee can cause pain, swelling, and joint effusion. The presence of a loose body on the x-ray and the absence of trauma or injury make this a diagnosis that should be considered.
- Rare Diagnoses
- Ganglion Cyst: A ganglion cyst is a benign lump that can occur in the joint, causing pain and swelling. Although rare, this diagnosis should be considered if other more common diagnoses are ruled out.
- Pigmented Villonodular Synovitis (PVNS): This is a rare condition characterized by the growth of tissue in the synovial membrane of the joint, which can cause joint effusion, pain, and swelling. The presence of joint effusion and a loose body on the x-ray make this a possible, although rare, diagnosis.