I am 71 years old and no spring chicken. I've had sacroiliac problems off and on for years. Usually it's a nagging ache in my low back. Now I'm having back and thigh pain. Can the sacroiliac joint cause pain in both areas?
Yes, but so can disc problems and kidney problems! It's impossible to tell without further testing. A disc problem in the upper lumbar spine (L3-L4) can cause these symptoms, but there will be other signs as well.
A recent study of older adults with thigh pain from L3-L4 disc herniation showed leg weakness and decreased reflexes were also common. These are signs of nerve pressure, most likely where the disc is pressing on the spinal nerve. Sacroiliac problems aren't usually accompanied by neurologic symptoms.
Kidney infections, tumors, and inflammation can cause back pain that radiates around the flank and down the thigh. Thigh pain alone is possible but uncommon. And when the kidney is involved there are usually other signs like blood in the urine, frequent urinating, or burning on urination.
New symptoms in older adults are a yellow flag to caution you. A medical exam would probably be a good idea to find out the exact cause of your problem.
Eran Tamir, MD, et al. Clinical Presentation and Anatomic Position of L3-L4 Disc Herniation. In Journal of Spinal Disorders. December 2004. Vol. 17. No. 6. Pp. 467-469.