<s>[INST] Hello... My husband knelt down today at work, and felt a sharp pain in his knee. It has since swollen up some, and is causing him allot of pain. He was perfectly ok before it happened. What could have happened so quickly and out of the blue like that? [/INST] dear madamIt seems that he has synovitis and may have strained one of the ligaments in the knee, it is advisable to put a compression bandage on the knee and take some over the counter painkillers for the time being and see an orthopedician ASAP to rule out any major issue. </s>