Sore thighs after getting up may be related to thigh fasciitis, lumbar disc herniation, ankylosing spondylitis and other diseases. Thigh fasciitis can cause localized sterile inflammation, and if combined with cold irritation during sleep at night, symptoms such as soreness and pain will occur after getting up. Herniated lumbar intervertebral discs and lumbar spinal stenosis compress the nerve roots in the legs, and if you sleep in an incorrect position or are exposed to cold during the night, it may aggravate the irritation of the intervertebral discs on the nerve roots, and you may experience soreness and pain in the legs when you get up. When the symptoms of ankylosing spondylitis are severe, the legs and the lumbosacral region may become sore and painful when you wake up in the morning. If you have thigh pain after waking up, it is recommended that you go to the hospital for medical examination and receive regular treatment.