Hi Andrew,
All I can give you is my personal experience. I fractured my elbow when I was a teenager. After having it in a cast for some time my muscles were shriveled and my arm was left in a crooked position. It was quite painful and it took some time to get it straightened out again but it did and I fully recovered. 25 years later I have had no problem with it. I suggest you call your doctor and get a timeline on long it should take and some exercises/stretches that might help speed your rehabilitation. Good luck.