Falling and popping your knee out at an odd angle is never a good thing. At best, it will only be a sprain for a few days. At worst, you will dislocate the joint and it will be painful for days and require a doctor's immediate attention. If the knee popped itself back into position, there is still some possible damage to the ligaments and tendons. Your doctor may prescribe several treatments to make sure the knee repairs itself properly.
If you have been diagnosed with moderate to severe sleep apnea, your doctor may recommend that you use a continuous positive airway pressure (CPAP) machine while you are sleeping in order to control your symptoms. Your doctor will then write you a prescription for a CPAP machine, and you should start sleeping more soundly once you begin using it. Many people who have been diagnosed with sleep apnea don't know what to expect after their diagnosis and as their treatment begins.