Your legs support you all day. Give them a good rest tonight.
Support under thighs and knees to relax back muscles.
Do you have big buttock and thighs and somewhat smaller waistline? You might have what we call a pear-shaped body. Beautiful body shape, by the way. If you are side sleeper, you should definitely have some support between your knees and leg. But if you sleep on your back, you definitely need a "Leg Pillow" to support under your knees and thighs to relax back muscles.
KNEES AND THIGHS
Use leg pillow under knees to relieve the pressure in the knees.
The pillow is wide enough to support the calves and knees. Never use pillow under your calves alone and leave your knees unsupported.
RELAX BACK MUSCLES
Your back muscles are much less strained when your legs are supported.