Sudden stiff knee - is this a clot?

[Badgerstriper]

Yesterday after work (desk based job) I came home and discovered when I was climbing the stairs that my left knee hurt when I bent it. It got steadily stiffer/sorer over the course of the evening and is still the same this morning.
I didn’t fall, twist it or injure it in any way so I’m mystified! I have a couple of long term health conditions but nothing that would cause this.
I Recently started on a POP (Noriday) which mentions increased risk of blood clots and if I’m being honest it’s preyed on my mind since I’ve started.
Has anyone had experience of a blood clot causing limb stiffness around the joint or pain? It’s not red or swollen or hot. I’m probably going to try to get a Gp appointment today since it came on so suddenly and without any clear cause.

Please get it checked out today. They might refer you to a DVT clinic where a simple DDimer blood test and a full assessment would either suspect or rule out a clot. Depending on your area you might get a Doppler today. Alternatively it could be MSK or a Bakers cyst.
But please get it seen.

Thank you. I got an appointment for 9am and the doc examined me thoroughly and said that it’s not a clot, although she wasn’t sure what it could be. I’ve to wait and see how it is over the next few day, but to get back to her if anything changes.
it’s put my mind at rest a bit (I’m a terrible worrier!) but I’m still struggling to bend my knee.