Painful and swollen knees
KNEE effusions can be caused by trauma (acute), systemic disease (acute or recurrent) or by overuse (recurrent). The history provides the diagnosis the majority of the time and is confirmed with a careful clinical examination.
The most common traumatic causes of knee effusion are injury to ligaments or menisci or a fracture. The most common non-traumatic cause is arthritis, but crystal deposition (gout/pseudogout) is also common and it is important not to miss an infection or tumour. A joint effusion without trauma is a very specific sign of joint inflammation, but other symptoms that