Symptoms

Signs and symptoms typically include:

• Swelling. The skin around your kneecap can puff up noticeably, especially when you compare the affected knee to the normal one.
• Stiffness. When your knee joint contains excess fluid, you might not be able to bend or straighten your leg completely.
• Pain. Depending on the cause of the fluid buildup, the knee might be very painful — to the point that it's difficult or impossible to bear weight on it.

When to see a doctor

See your doctor if:

• Self-care measures or prescribed medications don't relieve the pain and swelling
• One knee becomes red and feels warm to the touch compared to your other knee