Differential Diagnosis for Knee Lump
- Single most likely diagnosis
- Prepatellar bursitis: This condition, also known as housemaid's knee, is characterized by swelling and inflammation of the bursa in front of the kneecap (patella). The patient's description of a lump on the knee with onset on 5/29 and 4/10 pain is consistent with this diagnosis. The absence of warmth, fever, and normal skin color also supports this diagnosis.
- Other Likely diagnoses
- Osteochondroma: A benign bone tumor that can cause a lump on the knee. Although it's a possible cause, the acute onset on 5/29 makes it less likely.
- Ganglion cyst: A non-cancerous lump that can occur on the knee, often associated with a joint or tendon. The patient's symptoms could be consistent with a ganglion cyst.
- Lipoma: A benign fatty tumor that can cause a lump on the knee. The description of the lump as a "1/2 egg" size is consistent with a lipoma.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
- Septic arthritis: Although the patient denies fever and the skin is not warm to touch, septic arthritis is a medical emergency that requires prompt attention. If left untreated, it can lead to serious complications, including joint destruction and systemic infection.
- Soft tissue sarcoma: A rare but aggressive type of cancer that can cause a lump on the knee. Although unlikely, it's essential to consider this diagnosis to ensure prompt treatment if necessary.
- Rare diagnoses
- Synovial chondromatosis: A rare condition characterized by the growth of cartilage in the joint, which can cause a lump on the knee.
- Pigmented villonodular synovitis (PVNS): A rare condition that causes inflammation and overgrowth of the joint lining, leading to a lump on the knee.