Morning stiffness or pain in the leg and back that eases as the day goes on is usually muscular, often from sleep posture or mild nerve pressure in the lower back. Pain toward the back of the abdomen alongside this is worth checking separately, since that area can sometimes point toward the kidneys rather than the muscles.
Next Steps
Gentle stretching, a warm compress, and good hydration usually help the muscular pain. If the pain near your flank continues, ask your doctor for a urine test to rule out a
kidney cause.
Health Tips
See a physician if you notice fever, blood in your urine, or pain that doesn't ease through the day, since those need a proper examination.