Many people with multiple sclerosis have stiff muscles and spasms, a condition called spasticity. It happens mostly in the muscles of the legs and arms, and it may keep you from moving your limbs freely.
You might feel spasticity either as stiffness that doesn’t go away or as movements you can’t control that come and go, especially at night. It can feel like a muscle tightening, or it can be very painful. Spasticity also can make you ache or feel tight in and around your joints and low back.