Differential Diagnosis
- Single most likely diagnosis
- Osteoarthritis: The mild narrowing of the left femorotibial joint compartment and osteopenic bones suggest a degenerative joint disease, with osteoarthritis being the most common cause.
- Other Likely diagnoses
- Old fracture or trauma: The well-corticated osseous protuberance arising from the lateral femoral condyle and the mention of sequelae of prior trauma suggest that the patient may have had a previous fracture or injury that has healed.
- Bone cyst or benign tumor: The osseous protuberance could also be a bone cyst or a benign tumor, such as an osteochondroma, although this is less likely given the description of the lesion as well-corticated and possibly related to prior trauma.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Osteosarcoma: Although rare, osteosarcoma is a malignant bone tumor that can present with a similar appearance to a benign lesion, and it is essential to consider this possibility to ensure prompt diagnosis and treatment.
- Infection (e.g., osteomyelitis): Infection can cause bone destruction and narrowing of the joint space, and it is crucial to rule out this possibility, especially if the patient has a history of trauma or immune compromise.
- Rare diagnoses
- Osteochondritis dissecans: This is a rare condition where a piece of cartilage and bone becomes detached from the surrounding bone, which could potentially cause a well-corticated osseous protuberance.
- Fibrous dysarmenia: A rare genetic disorder that can cause bone deformities and osteopenia, although this would likely be associated with more widespread and severe bone abnormalities.