I have a knee injury and was immobile for 6 weeks, now able to move about n walk on flat surfaces etc. the knee is stiff and some discomfort, which is expected. My main problem is muscel weakness and feels as my body is shaky on the inside, also balance problems, fatigue and body aches.
Muscle weakness knee stiffness are obviously due to immobility. As you start movement after long time, it will take time to loosen up the joint. Similarly, muscles will take time to regain their strength along with knee movement. Muscles are responsible for holding you knee, so as your muscles start getting strength - problem and discomfort due to equilibrium will be solved. Patience and physiotherapy will be helpful.