Differential Diagnosis for Atraumatic Right Knee Pain
- Single most likely diagnosis
- Prepatellar bursitis: This condition is likely given the history of an abrasion over the knee, which can cause irritation and inflammation of the prepatellar bursa, leading to pain and swelling. The pain is typically a dull ache and worsens with bending or kneeling.
- Other Likely diagnoses
- Osteoarthritis: Although the patient's age is relatively young for primary osteoarthritis, the condition can still occur, especially if there's a history of trauma or repetitive stress on the joint. The pain description and exacerbation with bending are consistent with osteoarthritis.
- Meniscal tear or ligament sprain: Even though the pain is described as atraumatic, minor, unnoticed trauma or overuse could lead to a meniscal tear or ligament sprain, causing knee pain that worsens with bending.
- Tendinitis: Patellar tendinitis (jumper's knee) could be a consideration, especially if the patient has recently increased their physical activity level, leading to overuse of the patellar tendon.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Septic arthritis: Despite the denial of redness/discharge and no signs of septic arthritis, it's crucial to consider this diagnosis, especially if the patient is immunocompromised or has a history of intravenous drug use. Septic arthritis is a medical emergency requiring prompt treatment.
- Osteonecrosis: Although less common, osteonecrosis (avascular necrosis) of the knee could present with atraumatic pain and should be considered, especially if the patient has risk factors such as long-term corticosteroid use or excessive alcohol consumption.
- Bone tumor: A primary or metastatic bone tumor could cause knee pain, and although rare, missing this diagnosis could have severe consequences.
- Rare diagnoses
- Pigmented villonodular synovitis (PVNS): A rare condition characterized by benign growths in the synovium, leading to knee pain and swelling.
- Synovial chondromatosis: A rare condition where cartilage grows in the synovium, causing joint pain and swelling.
- Rheumatoid arthritis: Although less likely given the lack of systemic symptoms and the focal nature of the pain, rheumatoid arthritis could still be a consideration, especially if the patient has a family history or other suggestive symptoms.