I've fallen and my rt knee was bent behind me and a landed on it i have severe pain to the outer side of the knee and underneath the back of the knee. the pain radiates down the tibula and fibula down to the foot. when i try to stand or move the nknee i

Without : Without an xray and examination, it is very difficult to know for sure what you have done to your knee/leg. The most common possibilities include a fracture, ligament sprains or tears, cartilage tears, and a deep contusion/bruise to the bone/joint. You really should be evaluated as soon as possible by an orthopedic surgeon, or perhaps at least in a minor emergency room. In an er, xrays can be taken to evaluate for a broken bone. If it is more of a soft tissue injury, and if the diagnosis remains unclear after a physical exam by the physician, an MRI may be needed for additional information.