A 12 year old boy presents with painful swollen knee after a sudden fall. Which bursa is most likely to be affected?

The key is B. Prepatellar bursa. [A fall onto the knee can damage the prepatellar bursa. This usually causes bleeding into the bursa sac causing swellen painful knee. Prepatellar bursitis that is caused by a injury will usually go away on its own. The body will absorb the blood in the bursa over several weeks, and the bursa should return to normal. If swelling in the bursa is causing a slow recovery, a needle may be inserted to drain the blood and speed up the process. There is a slight risk of infection in putting a needle into the bursa].