Differential Diagnosis for Knee Injury
- Single most likely diagnosis
- Meniscal tear with fragment displacement: This is the most likely diagnosis given the specific description of a small radial tear in the mid posterior horn of the medial meniscus with a subtle anteriorly displaced fragment. The presence of a meniscal tear is a common cause of knee pain and mechanical symptoms, especially with evidence of a displaced fragment.
- Other Likely diagnoses
- Osteoarthritis (OA) of the knee: The mention of mild tricompartmental OA suggests that the patient's symptoms could also be attributed to or exacerbated by the degenerative changes associated with OA. This condition can cause pain, stiffness, and limited mobility in the knee.
- Meniscal cyst: Although not directly mentioned, the presence of a meniscal tear could potentially be associated with a meniscal cyst, especially if the tear is communicating with the joint surface. Meniscal cysts can cause localized pain and swelling.
- Do Not Miss diagnoses
- Ligamentous injury (e.g., ACL, MCL): It is crucial not to miss a ligamentous injury, as these can significantly impact knee stability and require different management strategies. The mechanism of injury that caused the meniscal tear could also have resulted in ligamentous damage.
- Osteonecrosis: While less likely given the description, osteonecrosis (avascular necrosis) of the femoral condyle or other parts of the knee could present with similar symptoms and must be considered, especially if the patient has risk factors such as steroid use or significant trauma.
- Rare diagnoses
- Meniscal ossicle: A rare condition where a small ossification forms within the meniscus, potentially causing symptoms similar to a meniscal tear.
- Synovial chondromatosis: A condition characterized by the formation of cartilaginous nodules within the synovium of the knee joint, which could cause mechanical symptoms and joint pain, although it is much less common than meniscal tears or OA.