Differential Diagnosis for Mild Prepatellar Swelling

Single Most Likely Diagnosis

• Prepatellar Bursitis: This condition, also known as housemaid's knee, is the most common cause of prepatellar swelling. It occurs due to inflammation of the prepatellar bursa, which can be caused by repetitive kneeling, direct trauma, or infection. The swelling is usually mild to moderate and may be accompanied by pain and redness.

Other Likely Diagnoses

• Septic Arthritis: Although less common than prepatellar bursitis, septic arthritis of the knee joint can cause prepatellar swelling, especially if the infection spreads to the surrounding tissues. It is characterized by severe pain, significant swelling, redness, and warmth around the knee.
• Patellar Tendinopathy: Also known as jumper's knee, this condition involves inflammation of the patellar tendon, which can cause swelling and pain in the prepatellar region. It is common in athletes who participate in sports that involve jumping.
• Osgood-Schlatter Disease: This condition is characterized by inflammation of the tibial tubercle, where the patellar tendon attaches to the tibia. It can cause swelling and pain below the knee, but may also involve the prepatellar region.

Do Not Miss Diagnoses

• Deep Vein Thrombosis (DVT): Although DVT typically presents with swelling, pain, and discoloration of the lower leg, in rare cases, it can cause swelling in the prepatellar region if the clot is located in the proximal veins. Missing this diagnosis can be life-threatening due to the risk of pulmonary embolism.
• Cellulitis: A bacterial infection of the skin and subcutaneous tissues, cellulitis can cause significant swelling, redness, and warmth. If left untreated, it can lead to serious complications, including sepsis.
• Necrotizing Fasciitis: A rare but life-threatening infection of the fascia, necrotizing fasciitis can cause severe pain, swelling, and skin necrosis. It requires immediate medical attention to prevent mortality.

Rare Diagnoses

• Lipoma or Other Soft Tissue Tumors: Benign tumors such as lipomas can cause swelling in the prepatellar region, although this is relatively rare.
• Gout or Pseudogout: These conditions typically affect the joints, but in rare cases, they can cause swelling and inflammation in the prepatellar region.
• Hemophilia: In patients with hemophilia, bleeding into the soft tissues can cause swelling, including in the prepatellar region. However, this would typically be accompanied by a history of bleeding disorders.