What is a Bursa?
A bursa is a “potential space” which develops between two layers of tissue that move across each other that would otherwise create friction. Usually they are microscopically thin but they can fill with fluid either as a normal process to protect from friction or due problems such as inflammation or infection.
Is It Normal to Have a Bursa?
Everyone has bursas throughout their body. The knee has at least 6 and sometimes up to 13 bursas around it. Some bursas exist in everyone – like the one that protects the rotator cuff in the shoulder. Others can develop as protective response to friction (like in the front of the foot) or as a response to infection or injury.
Where in the Body Do Bursa’s Occur?
Normal locations for bursas include;
- The shoulder
- The lateral ‘point’ of the hip
- The point of the elbow
- The knee
- The feet
Why Does an Enlarged Bursa Mean?
Firstly, there is no absolute consensus in ‘normal’ bursa sizes. An enlarged bursa can be a completely painless and normal process to protect from friction. An example is that swimmers have large bursas in their shoulders to protect them from repetitive shoulder movements. Seeing an enlarged bursa on a scan does not mean the cause of pain has been found!!
An enlarged bursa can mean,
- A normal process responding to normal friction
- A normal response to abnormal friction (an injury, bone spur or weakness leading to the extra friction)
- A response to direct trauma (typically at the knee and elbow bursas)
- A pathological process such as infection or even gout
Why Does Bursitis Cause Pain?
Many types of bursitis cause no pain at all (even when there is a lot of swelling). Bursitis can cause pain when it leads to excessive inflammation, infection or compression that stops surrounding structures from working normally. Sometimes bursitis appears painful because it is a part of a more widespread problem like greater trochanteric pain syndrome or shoulder impingement.
How is Bursitis Treated?
The treatment for bursitis depends entirely on the type and the cause. Many cases of bursitis are a normal response to trauma or friction and need no treatment at all. Sometimes an inflammatory bursitis needs to be treated first so that the underlying cause can be addressed – this is often true in the shoulder or hip where a corticosteroid injection can reduce the pain and inflammation long enough to correct the underlying problems. Infective bursitis is entirely different and should never be treated with a corticosteroid injection which can worsen the problem. A correct diagnosis, antibiotic treatment and sometimes even a surgical washout can be required in these cases.