Well, like you and most everyone here, I'd get up, walk around a bit to *loosen* the knee, grab some ice and pop a pain pill if on schedule. I'd read and then typically fall back asleep within an hour or two. I took daytime naps whenever the sleep-fairy struck and she struck often! I'd never experienced such exhaustion in my life, even after a hip replacement.
If I remember correctly, I had my first night of a solid 5 hours sleep at around 5 weeks, in my husband's old recliner. It was definitely cause for celebration!

From the five hour point, things quickly returned to *normal*, which is about 7 hours a night for me. I'd say this occurred at the 6-7 week point when my knee became a bit less...er...vocal. It mellowed from a high pitched scream at 5 A.M. to a low-pitched grumble at 7 A.M..
I should also note that my sleeping pattern improved greatly once I was off the Oxy and I was "Oxy-Free at 5 weeks. Though it did a great job with pain, and I certainly needed it for the first 5 weeks, it made my head *buzz,* in such a way that deep sleep didn't occur for any length of time. If I didn't take them at night during those first few weeks, I knew what would happen; things would get ugly fast with pain spiraling out of control, so I took them right on schedule to avoid that scenario.