My 10 year old son is complaining of a constant pain in the back of his knee that has only started 3 hours ago. he has no bruising and can not remember injuring his knee. The pain is constant even when the leg is stationary and no repositioning seems to sooth the pain.
Most common cause of pain at back of knee is injury. Inury may very trivial that may not notice, give painkiller like ibuprofen200 thrice a day for 2 day and inform the condition