Why was fluid drained from my knee before the injection?

Relief and a better injection

A knee full of fluid feels tight and stiff and is hard to bend. Drawing it off, called aspiration, usually brings quick relief. It also means the medicine injected afterwards is not diluted by a large volume of fluid, and the joint can be entered more accurately.

What the fluid can tell your doctor

The look of the fluid gives early clues, and laboratory tests add detail:

• Clear, straw-coloured fluid is typical of arthritis or irritation after overuse
• Blood-stained fluid after an injury can point to a ligament tear or fracture
• Cloudy fluid raises concern for inflammation or infection
• Crystals under the microscope can confirm gout or pseudogout
• A cell count and culture help diagnose or exclude septic arthritis

When the injection is postponed

If the fluid looks cloudy or the knee is hot, red and very painful, a steroid injection is usually held back until infection has been excluded. Injecting steroid into an infected joint could make things worse. In that situation the sample is sent urgently and treatment is guided by the result. A knee with sudden swelling and fever needs same-day medical attention.

Does the swelling come back?

It can, because aspiration removes fluid but not the reason it formed. Repeated swelling is a signal to look for the underlying cause, which may need imaging, blood tests or a review of the treatment plan with a knee specialist in Doha.