Frustrating, isn't it?
I came down with a cold, and injured my wrist, within a day of each other. On 2nd October, my CTL was 65. By 10th November I'd managed to train twice and my CTL dropped as low as 26 as I started ramping back up on the 17th. My CTL will only recover to 39 by this Friday, after 4 weeks, so it will likely be February before I'm back where I was 4 months previously.
=> I hope that you recover from your cold faster than I did and that your knee isn't as badly hurt as you fear.