Sometimes the cause of low back pain occurs with injuries to the sacroiliac (SI) joint and ligaments.
There are two SI joints. Each is located on either side of the sacrum. SI joints are small and very strong, providing structural support and stability. They function as shock absorbers for the pelvis and the low back, dispersing the forces of the upper body. Whenever an SI joint is irritated or injured, the resultant joint dysfunction may cause pain in the lower back and legs.
The most common symptom is pain in the low back that is aggravated by sitting, standing, and bending at the waist. When SI joint dysfunction is severe, there can be referred pain into the hip, groin, and leg.
Sacroiliac joint dysfunction is difficult to diagnose. This is because the pain patterns associated with SI joint dysfunction are frequently mistaken for nerve irritation in the low back, muscle sprain, or hip bursitis.