Can you get a stiff knee at night? It happens a lot with me.
Night Stiffness: Can you get a stiff knee at... - Stand Up 2 OA
Yes, my knee gets stiff after long times of immobility, such as sleeping.
Yes I think you can, keep doing exercises. Mind, as I said, I've only had a partial replacement on the 22/11/19 and obviously still on the road to recovery. Tendons are only like elastic bands, even elastic bands become stiff and will snap. I'm a Complementary Therapist of 22 years and have Anatomy & Physiology, so do know a bit about that body system.