Here is a stretch for your knees.

Unlike the neck and shoulders, where stiffness is often the main issue, stretching is crucial for improving the range of motion in your knees and alleviating pain.

Sit near the edge of a chair and extend one leg straight out.
Place both hands just above the knee of the extended leg and gently press down until the knee is fully straightened.
A key point here is to keep your heel on the floor while flexing your toes upward.
Also, be mindful not to let your back round.
Once you have pressed down to the point where the knee is fully straight and you feel a stretch along the back of your thigh, hold the position for 30 seconds, then release.

Perform this stretch three times for each leg.