Pigmented villonodular synovitis (PVNS) is a joint problem that
usually affects the hip or knee. It can also occur in the
shoulder, ankle, elbow, hand or foot. When you have PVNS, the
lining of a joint becomes swollen and grows. This growth harms
the bone around the joint. The lining also makes extra fluid
that can cause swelling and make movement very painful. PVNS
isn't common. It can affect anyone, but it is most common in
people 20 to 45 years old. It may happen slightly more often in
men. If you have PVNS, you'll notice swelling and stiffness in a
joint, most often your knee. The joint may hurt. You may have a
"popping" feeling when you move the joint. The symptoms usually
appear gradually and may come and go over time. Doctors don't
know exactly what causes PVNS. It doesn't seem to run in
families. It doesn't seem to be caused by certain jobs or
activities. PVNS can look like arthritis and some other joint
conditions. Your doctor may use tests to check for these
conditions. After a physical exam, your d