What is the fluid in bursitis?

A healthy bursa contains a thin film of fluid that lets tissues glide with little friction. Irritation makes its lining inflamed and more fluid accumulates. Superficial bursae, such as those over the elbow or kneecap, may then form an obvious pouch-like swelling.

Appearance alone cannot establish the cause. Repeated pressure or injury can produce non-infected inflammation, while bacteria or crystals may create a similar swelling. A clinician uses skin changes, tenderness, medical history and sometimes a sample of fluid to tell these possibilities apart.

Keep direct pressure off the swelling and modify the activity that triggered it. A protective pad can help at the elbow or knee. Do not massage forcefully, insert a needle or repeatedly test the swelling by pressing it, because this can aggravate tissue or introduce bacteria.

Fluid does not always need removal. Aspiration may be useful when infection or crystal disease is suspected, or when a large collection requires clinical management. The decision depends on the bursa involved, the skin over it and the chance that fluid will return.

Prompt assessment is needed when swelling is accompanied by spreading redness, marked warmth, worsening tenderness, fever, chills, pus or broken skin. These findings can indicate an infected bursa, particularly after a scrape or puncture.

Have persistent or recurrent swelling checked even without those warning signs if movement is restricted or the diagnosis is unclear. Seek urgent help after major trauma, or if severe pain and swelling make it impossible to use the nearby joint normally.

Ask whether the fluid is likely due to pressure, infection or crystals, and whether sampling would change treatment. If aspiration is proposed, ask how the skin will be protected, what the sample will be checked for and how to limit renewed pressure while the bursa recovers.