We have many bursa's in the human body. They lie between muscle and muscle or between muscle and bone. Their main purpose is to prevent over frictions of the muscle tendons and allow smooth movements.
Bursa's can be described as a fluid filled plastic bag that sits underneath the muscle tendons or between the tendons and bone. The reason why they get inflamed is not due to the bursa themselves. The bursa has just become irritated due to other structures forcing the tendons that lie between it to overwork. In order to treat the condition we need to understand what is causing the bursa to overwork. Most commonly it is due to a bio-mechanical imbalance or a repetitive movement. Common bursa's that become inflamed are the patella bursa, hip bursa and the shoulder bursa.