If you do decide to head to the doctor after a loud pop in knee followed by pain, you should expect to undergo a variety of tests. Firstly though, a doctor will look for swelling and bruising while asking you questions about your accident. They will also try to bend and rotate your knee a bit to see how it moves and where the pain is. Lastly, you will probably undergo either an X-ray, a CT scan, or an MRI so that your doctor can get a clear picture of your injury.