Pre-patellar bursitis is inflammation in the pre-patellar bursa, appearing as a tense swelling in front of the kneecap and discreet from the kneecap bone itself.
This is usually an overuse condition, such as a person might develop who habitually works on their knee, eg scrubbing floors. Usually it is inflammatory, but sometimes a foreign-body, such as a needle shard, may have penetrated and be the cause of an acute infection