<human>: I am experiencing a throbbing ache and severe fatigue behind my right knee (more in the crease behind it than the knee cap) when I stand for more than an hour or so.  This has been going on a few weeks and now it has started waking me up at night too.  Any ideas what may be the cause?
<bot>: Hello, I want to know one thing had you ever met an accident or fell down? The throbbing pain in knee has many causes like meniscus tear: occurs due to sudden twist of the knee, ligament injury or sprain it occurs when the knee over extended or any over strain on front of bent knee, muscle injury or muscle strain, arthritis.This occurs due to knee injury or over strain on knee. But you have pain behind the knee cap or knee. Then the other causes along with are bakers cyst or PCL tear and also other possibilities of gout in this condition uric acid forms crystals and accumulate in joints and leads to pain behind the knee and also occurs other part of the knee, deep vein thrombosis, rheumatoid arthritis and tendinitis. But to rule out the exact cause get X-ray or MRI and consult the or tho.