Differential Diagnosis for Knee Pain
The patient's symptoms of knee pain, locking, and difficulty with certain movements after a fall suggest several possible diagnoses. Here's a categorized differential diagnosis:
Single most likely diagnosis
- Medial meniscus tear: The location of the pain on the medial aspect of the knee, along with locking and worsening pain when the knees touch, is highly suggestive of a meniscus injury, particularly a medial meniscus tear. The mechanism of injury (slipping and falling) and the nature of the symptoms (locking, pain with specific movements) align well with this diagnosis.
Other Likely diagnoses
- Medial collateral ligament (MCL) sprain: Given the medial location of the pain and the mechanism of injury, an MCL sprain is a plausible diagnosis. However, the presence of locking and the specific pattern of pain radiation might be less typical for an isolated MCL injury.
- Osteochondral defect: This could be considered, especially if the fall resulted in a direct blow to the knee or a twisting injury that could cause a piece of cartilage and bone to become damaged or detached, leading to locking and pain.
- Patellofemoral pain syndrome: Although less likely given the specific location of the pain and the locking symptoms, patellofemoral pain syndrome could be considered, especially if the patient has a history of knee problems or if the pain is exacerbated by activities that increase patellofemoral stress.
Do Not Miss diagnoses
- Septic arthritis: Although the patient does not have significant bruising or severe swelling, and there's no mention of fever or systemic symptoms, septic arthritis is a condition that must be considered, especially if the patient is immunocompromised or has a history of joint injections or recent surgery. It's a medical emergency that requires prompt diagnosis and treatment.
- Fracture: A fracture, particularly of the tibial plateau or the femoral condyles, could present with similar symptoms and must be ruled out, especially given the mechanism of injury. The absence of severe swelling or bruising does not exclude this possibility.
- Deep vein thrombosis (DVT): Given the recent trauma and potential for immobilization, DVT should be considered, especially if there are symptoms such as calf swelling, redness, or warmth.
Rare diagnoses
- Osteonecrosis: This could be a consideration if the patient has risk factors such as long-term steroid use, excessive alcohol consumption, or certain medical conditions. However, it would be less likely in the acute setting following a fall without these predisposing factors.
- Plica syndrome: This is a rare condition where folds in the synovial tissue cause knee pain and locking. It's less common and would be considered if other diagnoses are ruled out and the patient's symptoms persist.