Lower back pain on the right side can be caused by numerous factors. According to the National Institute of Neurological Disorders and Stroke, or NINDS--a division of the National Institutes of Health--a person's back is comprised of an intricate arrangement of bones, muscles and connective tissue that run from the neck to the pelvis. Musculoskeletal problems can arise in any part of the back, including the lower right side.
Herniated Lumbar Disc
A herniated lumbar disc can cause low back pain on the right side. A disc herniation involves a rupture of the disc's fibrous outer ring and resultant slipping of the disc's center, or nucleus, into the spinal canal. According to the Spine Health website, approximately 90 percent of intervertebral disc herniations occur toward the bottom of the spine, between the fourth and fifth lumbar vertebrae or the fifth lumbar vertebra and the first sacral segment. If the disc herniation impinges the nerve root--an offshoot of the the spinal cord--on the right side of the spine where it exits the vertebral column through a small hole called the intervertberal foramen, right-sided low back pain, along with right-sided leg pain, may result. Most lumbar disc herniations occur in a posterolateral direction, which means the bulge or herniated disc material extends outward from the disc itself somewhere between the back and side of the disc. The side of the disc that ruptures or bulges depends on the mechanism of low back injury, or the particular forces acting on the body when the injury occurred.
Quadratus Lumborum Trigger Points
Quadratus lumborum muscle trigger points can cause right-sided low back pain. The QL muscle is a paired muscle that is quadrilateral in shape. It runs from the rear crest of the pelvis to the last rib and the transverse processes of the lumbar vertebrae, which are situated on the sides of the vertebra bones. Acting by itself, the QL helps the spine bend laterally or to the side. When both QL muscles act together, they help depress or lower the rib cage. According to the American Academy of Family Physicians, or AAFP, the QL muscles, along with other muscles that help maintain the body's posture, are a common location for myofascial trigger points, or MFTPs--hyperirritable nodules or knots within a tight band of muscle. MFTPs can often be found in the right QL, left QL or both QLs, and may be painful without provocation or when they are pressed or squeezed. The AAFP notes that people who have MFTPs, including MFTPs in the lower aspect of the right QL, frequently report regional persistent pain that causes a reduced range of motion in that muscle.
Sacroiliac Joint Dysfunction
Right-sided sacroiliac, or SI, joint dysfunction can cause right-sided lower back pain. The SI joints are paired joints located between the sacrum and iliac, or hip, bones in the low back, and constitute the rear part of the pelvic girdle. According to the Sports Injury Clinic website, SI joint dysfunction occurs when there is too much or too little movement within one or both SI joints. If there is too much joint movement, the ligaments surrounding the SI joint may be lax or sprained. If there is too little joint movement, the SI joint may be locked, or hypomobile. Both scenarios can affect the balance of the pelvis and may cause pain in the low back, buttocks, thigh or groin, notes the Sports Injury Clinic website. If the right SI joint is affected, it's likely that pain or discomfort will manifest on the right side, although it's possible for right-sided SI joint dysfunction to produce left-sided symptoms, and vice versa. SI joint-related low back pain can range from deep, dull and achy to sharp and stabbing, and can significantly restrict movement.