Have you talked to your neuro about Physical Therapy (PT)?

Exercise and stretching can be beneficial for spasticity. Not everyone will have pain with spasticity although it is common.

My legs are exactly like yours - stiff and my knees don't like to bend, I hate stairs and curbs but will do them. My legs have been like that for a long time.

When I was dx'd my neuro told me if I do nothing else, walk. That was in 1986 and I still walk. I use a treadmill and do quite a bit of stretching.

Will my approach work for you? I have no idea, maybe, maybe not. Each of us are different and what works for one will not work for someone else.

I need the stiffness it's what helps keep me walking. I have quite a bit of weakness in my legs and always have. If I lose the stiffness I will not be walking -guaranteed.

Again - talk to your doctor about exercise and/or PT