The features are consistent with superficial infrapatellar bursitis.

The superficial infrapatellar bursa lies between the subcutaneous tissues and the upper part of the patellar ligament.

The superficial infrapatellar bursa is vulnerable to injury from both acute trauma and repeated microtrauma. Acute injuries are caused by direct trauma to the bursa during falls onto the knee or patellar fracture. Overuse injuries are caused by running on soft or uneven surfaces or doing jobs that require crawling or kneeling.