What Causes Pain And Burning Sensation In The Knees?

I WAS MOVING A CASE HERE AT MY WORK ON MY HANDS AND KNEES AND USING MY KNEE TO PUSH WITH AND ALL OF SUDDEN A SHARP LIKE BURNING NEEDLE PAIN SAID I HAD TO STOP , NOW EVERYTIME I PUT MY KNEE TO THE FLOOR, OR USE IT IN THE TUB TO GET OUT, OR USE IT TO GET IN BED THOSE NEEDLE LIKE BURNING PAIN ABOUT PUTS ME FLAT TO THE FLOOR...HAVE BEEN TO HAVE XRAY AND SENT TO PYHSICAL THERAPY BUT THE PHYSICAL THERAPIST CANT FIND A TENDON, LIGAMENT OR ANYTHING SHE CAN WORK ON SO WE QUIT THAT AND SENT ME BACK TO DR AND THE WORKMANS COMP HAS SENT ME BACK TO FINISH THERAPY....CANT FIND ANYTHING TO WORK ON, SHE IS THINKING BRUISED BONE OR SOMETHING ELSE...NEVER HURTS UNLESS USE IT TO GET ON HANDS AND KNEES OR HIT IT....WHAT DO YOU THINK