Overview
Pain at the very bottom of the back — in the lower lumbar and sacral region — is extremely common and can have a wide range of causes. The area includes the lowest vertebrae (L4, L5), the sacrum (the triangular bone at the base of the spine), and the sacroiliac joints (where the spine meets the pelvis). Pain here can radiate to the buttocks, hips, and down the legs.
Common Causes
- Sacroiliac joint dysfunction — a common and often overlooked cause of low back and buttock pain
- Lumbar disc herniation — a slipped disc pressing on the sciatic nerve (sciatica)
- Lumbar spondylosis — age-related wear and tear of the lower spine
- Piriformis syndrome — the piriformis muscle irritating the sciatic nerve in the buttock
- Coccydynia — pain in the tailbone (coccyx), often after injury or prolonged sitting
- Ankylosing spondylitis — inflammatory arthritis affecting the sacroiliac joints
- Gluteal muscle tightness or strain
Treatment
- Physiotherapy — targeted exercises for the lumbar spine and sacroiliac joint
- Massage therapy
- Anti-inflammatory medications
- Heat and ice therapy
- Posture and ergonomic advice
- Sacroiliac joint injections if conservative measures fail
Posture Tips
Sitting for prolonged periods is a major aggravating factor. Take regular breaks from sitting, use a lumbar support cushion, and try to maintain a neutral spine position. Strengthening the core and gluteal muscles reduces strain on the lower back.