A swollen knee means there's a fluid on the knee. Page last reviewed: October I Next review due: October Knees are very prone to swelling and pain because they're weight-bearing.
The swelling occurs when fluid builds up in or around your knee joint. This is sometimes called water on the knee but is medically called an effusion.
The most common causes are:. Knee pain is also common. The onset of swelling and the type of pain varies depending on the cause. Inflammation, which causes swelling, can occur suddenly acute or gradually and last for a long time chronic.
Acute swelling is often caused by an injury and will disappear after a day. Chronic swelling can be a sign of an underlying medical condition. In many cases, swelling can be treated at home with painkillers and by elevating your leg. Signs of an infection are:. If your pain and swelling have come on suddenly, it may be due to an injury from playing sport or after an accident or fall.
Common injuries include:. If your swelling has come on gradually without any obvious trigger, it could be due to overuse of the knee joint.
