Hip arthritis frequently causes back pain. About half of people with hip osteoarthritis also report lower back pain, and in a study of patients who underwent hip replacement, two-thirds saw their back pain resolve or significantly improve afterward. The connection between the hip and spine is so well established that orthopedic specialists refer to it as “hip-spine syndrome,” a recognition that these two areas function as a single mechanical unit.
How the Hip and Spine Work Together
Your hip joints and lumbar spine share the work of nearly every movement you make on your feet. When you bend forward, sit down, or walk, the pelvis acts as a bridge between the two, coordinating how much motion each joint contributes. In a healthy body, this coordination is seamless. When you transition from standing to sitting, for example, your pelvis tilts backward, creating space for your thigh bone to flex into the hip socket. The lumbar spine adjusts its curve in response.
When hip arthritis stiffens that joint, the system breaks down. For every degree of pelvic motion lost, the thigh bone needs roughly one extra degree of flexion to compensate, and the lumbar spine must pick up whatever slack remains. Over time, this redistribution of movement overloads structures in the lower back that weren’t designed to handle it.
Three Ways Hip Arthritis Creates Back Pain
Postural Compensation
A stiff or painful hip changes how you stand. Hip arthritis commonly produces a fixed flexion deformity, meaning the hip can no longer fully straighten. To stay upright despite this, your lumbar spine increases its natural inward curve. This exaggerated lordosis compresses the joints and discs in the lower back, which can cause aching, stiffness, and in some cases nerve irritation. People with this pattern often notice their back feels worst after prolonged standing.
Sacroiliac Joint Stress
The sacroiliac (SI) joints sit just below the lumbar spine where the pelvis meets the base of the spine. Research using 3D imaging has found that people with hip osteoarthritis show significantly more degeneration in their SI joints compared to age-matched controls. The explanation is straightforward: as hip motion decreases, the SI joint absorbs more mechanical stress with each step, accelerating its wear. SI joint pain typically shows up as a deep ache on one side of the lower back or upper buttock.
Muscle Tension Through the Psoas
The psoas muscle is a direct physical link between your spine and your hip. It originates from the sides of your lower lumbar vertebrae, travels down through the pelvis, and attaches to the top of your thigh bone. Its primary job is hip flexion. When the hip joint is arthritic and painful, the psoas often tightens protectively or works harder to compensate for lost mobility. That sustained tension pulls on its attachment points along the lumbar spine, producing lower back pain that worsens with walking.
What This Pain Feels Like
Back pain caused by hip arthritis tends to be a dull, persistent ache in the lower lumbar region or around the SI joints, rather than a sharp or shooting pain. It often worsens with activity and improves with rest. One distinguishing clue: the back pain typically arrived after the hip symptoms, not before. Many people don’t realize their hip is the root cause because the hip pain itself can show up in unexpected places. Buttock pain is the most common referral area from a symptomatic hip, appearing in about 71% of patients in one study. Groin and thigh pain, the classically expected locations, were actually less common at 55% and 57%.
Interestingly, a direct nerve-based referral from the hip joint to the lower back does not appear to occur. In a study mapping pain patterns from confirmed hip pathology, lower lumbar referral was absent. This means the back pain isn’t the hip “sending” pain signals to your spine. Instead, it’s genuine mechanical stress in your back created by compensating for a bad hip.
How Doctors Tell the Difference
Sorting out whether your back pain comes from the spine, the hip, or both can be genuinely difficult because the symptoms overlap so much. A careful physical exam is the starting point. Doctors will test your hip’s range of motion separately from your spine’s, looking for which movements reproduce your pain. Internal rotation of the hip, which is typically the first motion lost in hip arthritis, is a key test. If rotating your hip inward reproduces your groin or buttock pain while spinal movements feel relatively normal, the hip is likely the primary problem.
Imaging studies, including X-rays of both the hip and lumbar spine, help identify structural changes in each area. In ambiguous cases, a diagnostic injection of numbing medication into the hip joint can be definitive. If the injection temporarily eliminates both your hip pain and your back pain, it confirms the hip as the primary source.
What Happens After Hip Replacement
Some of the strongest evidence for the hip-back connection comes from hip replacement outcomes. In a prospective study of 344 patients undergoing total hip replacement, 170 (49%) had lower back pain before surgery. Within one year after the procedure, back pain resolved completely in 66% of those patients. This improvement occurred even in many patients who had documented spine disorders like degenerative disc disease, suggesting the mechanical stress from the bad hip was a major contributor to their back symptoms.
One unexpected finding: about 20% of patients who had no back pain before surgery developed new lower back pain within the first year after hip replacement. This likely reflects the significant postural realignment that occurs when the hip’s mechanics change. Half of those patients improved on their own as their body adjusted.
Exercises That Address Both Areas
Because the hip-spine relationship is fundamentally about shared movement, improving hip mobility and strength can reduce the load your back has to carry. Physical therapists at the Hospital for Special Surgery recommend doing both strengthening and flexibility exercises three to four times per week.
For strength, the focus should be on movements that build stability around the hip joint: single-leg hip bridges, lateral band walks, lateral step-downs, and single-leg deadlifts. These exercises train the muscles that control pelvic alignment during walking, reducing the compensatory demands on the spine.
For flexibility, the priority is releasing the muscles that tighten in response to hip arthritis. A supine figure-four stretch targets the deep hip rotators. A half-kneeling hip flexor stretch lengthens the psoas, directly relieving its pull on the lumbar vertebrae. A supine hamstring stretch with a towel addresses the posterior chain, which tightens when the pelvis shifts into a compensatory tilt. If any of these exercises increase your hip or back pain, scale back the range of motion rather than pushing through it.
These exercises won’t reverse arthritis, but they can meaningfully reduce the secondary back pain it creates by restoring some of the hip mobility your spine is currently compensating for.