Do fractures, or tears always show up on X-rays and MRI's

A few weeks ago, I feel super hard on my kneecap while running down hill and falling right into gravel. Right away my knee hurt horribly. I couldn't walk on it, and it swelled up and bruised right away. I feel with so much force, that I had to get stitches in my hands, and my shirt was ripped open. I went in to the ER, and they thought that it looked fractured, but the X-rays didn't show anything. A few days later, I couldn't stand the pain anymore, and I went into the orthopedic, to see if maybe the fracture just didn't show. They said it was just bruised with hematoma. But after 11 days, it just seemed to be getting worse, so I went back in. That time I had an MRI, and they still couldn't find and fractures or tears. They said it's just very badly traumatized, and bruised to the bone with hematoma.They thought that the outside looks like I fractured it though. So, they put me on crutches for 2-4 weeks, but said they couldn't really do anything else for it at this time. A few months ago, the same thing happened to my wrist, and they said that it was just bruised up. But a few weeks later, they finally figured out it was fractured. Could the same thing be with my knee? I'm in constant pain, and I cant sleep it hurts so bad. It's still swollen, bruised, I cant stand on it, I cant move it or straighten out my leg, and I cant have anything touch it with out it hurting SUPER bad. It's also very hot compared to the other one and it looks different from the other. I also have this weird lump and hurts really bad whenever someone touches it too. Sometimes my toes, feet and bottom part of my leg go numb, and the my entire knee is just in chronic pain. It's been 19 days since this happened, and it just feels like it's getting worse everyday. Could they be missing something?

Imaging studies are far from perfect, and many times there are things that just don't show up.