The QL muscle, short for quadratus lumborum, is a deep muscle in your lower back that connects your pelvis to your lowest rib and spine. It sits on both sides of your lumbar spine, tucked behind your abdominal organs, and plays a key role in stabilizing your trunk, bending sideways, and even breathing. Despite being relatively small and hidden, it’s one of the most common sources of lower back pain.
Where the QL Sits in Your Body
The quadratus lumborum is a rectangular, flat muscle that runs along each side of your lower spine. It originates at the top of your pelvis (the inner lip of the iliac crest) and fans upward to attach to two places: the underside of your 12th rib (your lowest rib) and the bony side projections of your first through fourth lumbar vertebrae. A tough ligament called the iliolumbar ligament also anchors the muscle at its base.
Because of its position, the QL sits deep beneath the more superficial back muscles you can feel when you press along your spine. It’s sandwiched between the kidneys in front and the spinal erector muscles behind, making it difficult to access through simple touch. This deep placement is part of what makes QL problems tricky to identify and treat.
What the QL Muscle Does
The QL has three primary jobs. First, when one side contracts on its own, it bends your trunk to that side (lateral flexion). This is the motion you use when reaching down to pick something up off the floor beside you. Second, when both sides contract together, they help extend your spine, keeping you upright. Third, and less obviously, the QL anchors your 12th rib during breathing. When your diaphragm contracts to pull air into your lungs, the QL holds that bottom rib steady so the diaphragm has a stable platform to work from. Without this, deep breathing would be less efficient.
Beyond these active movements, the QL is a postural stabilizer. It works constantly during walking, standing, and sitting to keep your pelvis level and your spine aligned. If you carry a heavy bag on one side, your opposite QL is firing to prevent you from tipping over. This relentless stabilizing role is one reason the muscle is so prone to fatigue and tightness.
Why the QL Is a Common Source of Back Pain
Among people with low back pain, 30% to 55% have active trigger points in the quadratus lumborum. These are hyperirritable knots within taut bands of muscle fiber that produce both local tenderness and pain in distant areas. Even in people without back pain, up to 10% show latent trigger points in the QL that could become problematic under stress or overuse.
What makes QL pain confusing is where you feel it. Trigger points in the deeper fibers of the muscle send pain from the lower back down to the sacroiliac joint (where your spine meets your pelvis) and into the lower buttock. Trigger points in the more superficial fibers can refer pain along the outer hip, down the side of the thigh, and even into the groin. This wide referral pattern means QL problems are frequently mistaken for hip joint issues, sciatica, or sacroiliac dysfunction.
Common causes of QL irritation include prolonged sitting (especially with poor posture or a wallet in your back pocket), repetitive bending or twisting, sleeping on a sagging mattress, and leg length discrepancies that force one side of the QL to work harder than the other.
How QL Problems Are Identified
Because the QL sits so deep, standard imaging like X-rays won’t reveal muscle tightness or trigger points. A physical therapist or clinician typically identifies QL dysfunction through hands-on palpation, pressing into the muscle between the bottom rib and pelvis while you lie on your side. If firm pressure reproduces your familiar pain pattern, that’s a strong indicator.
More advanced assessment uses shear wave elastography, an ultrasound-based technique that measures how stiff the muscle tissue is by tracking how quickly sound waves travel through it. Stiffer tissue means higher wave speeds. Research suggests that measuring QL stiffness this way can catch early-stage problems before they show up on conventional imaging, making it useful for both diagnosis and tracking progress during treatment.
Stretches That Target the QL
Because the QL bends you to the side, the most effective stretches involve lateral movements that open up the opposite flank. A simple standing side stretch, where you reach one arm overhead and lean away from the tight side, directly lengthens the QL. Gate pose, done from a kneeling position with one leg extended to the side while you reach the opposite arm overhead, is another effective option that many physical therapists recommend.
Other useful stretches include:
- Triangle pose: a standing position with wide legs where you hinge sideways, reaching one hand toward your ankle while the other extends upward
- Spinal twist: lying on your back and dropping both knees to one side, which gently rotates and stretches the QL
- Knee-to-chest stretch: pulling one knee toward the opposite shoulder while lying down
- Child’s pose: kneeling with arms extended forward, especially when you walk your hands to one side to bias the stretch
Build up gradually if you’re new to these stretches. Some initial discomfort is normal but should ease within a few weeks. If you’re dealing with acute low back pain, avoid forward bends and stick to stretches you can do lying on your back, which put less compressive load on the spine.
Strengthening and Long-Term Management
Stretching alone won’t solve a chronically irritated QL. The muscle also needs to be strong enough to handle the stabilizing demands placed on it. Side planks are one of the most effective QL strengtheners because they require the muscle to hold your trunk rigid against gravity, mimicking its real-world stabilizing function. Start with a modified version on your knees if a full side plank is too challenging.
Farmer’s carries, where you hold a heavy weight in one hand and walk while keeping your trunk upright, train the opposite QL to resist lateral tilting under load. Suitcase deadlifts work the same pattern. These exercises build the kind of endurance the QL needs for daily tasks like carrying groceries, picking up children, or sitting at a desk for hours.
Addressing the root cause matters just as much as the exercises. If prolonged sitting is the trigger, setting a timer to stand and move every 30 to 45 minutes can reduce the sustained compression on the QL. If a leg length discrepancy is involved, a heel lift in one shoe may be enough to rebalance the load. For people whose QL pain is tied to breathing dysfunction (shallow, chest-dominant breathing), practicing diaphragmatic breathing helps the QL return to its supportive role rather than compensating for a poorly functioning diaphragm.
QL Nerve Blocks in Medical Settings
The QL has also become important in pain management beyond musculoskeletal rehab. A procedure called a quadratus lumborum block involves injecting local anesthetic around the muscle to numb a broad region spanning roughly from the mid-back down to the lower abdomen. This technique is used after abdominal, obstetric, gynecologic, and urologic surgeries to control postoperative pain. It offers broader coverage than older nerve block approaches and can reduce the need for opioid pain medication during recovery.