Why Does My Lower Back Pop When Doing Leg Raises?

The popping sound you hear from your lower back during leg raises almost always comes from one of three things: a tendon sliding over a bony prominence near the hip, a small gas bubble collapsing inside a spinal joint, or a subtle shift in your pelvis as it adjusts under load. In most cases the noise is harmless, but its frequency during leg raises specifically is not random. The movement places unusual demands on the hip flexors and lumbar spine simultaneously, creating conditions ripe for audible clicks and pops. Whether that sound deserves attention depends on whether pain comes with it and how consistently it shows up.

The Iliopsoas Tendon Is the Usual Suspect

The most common source of a pop or snap near the lower back during leg raises is not actually in the spine itself. It comes from the iliopsoas tendon, a thick band of tissue that runs from the lumbar spine and inner pelvis down to the upper thigh bone. When you raise your legs, you engage this hip flexor aggressively. As it contracts and slides over the bony rim of the pelvis or the front of the hip joint, it can catch and release with an audible snap. This is a form of what clinicians call snapping hip syndrome, and the internal type caused by the iliopsoas is the variety most relevant to leg raises.¹

People often assume the sound originates in the lumbar vertebrae because they feel it in the lower back region, but the iliopsoas has direct attachments to the lumbar spine. When it snaps over the pelvis, the vibration travels up that connection and feels like it is coming from the spine. The snap typically requires active contraction of the hip flexors, which is exactly what a leg raise demands.¹

The good news is that painless snapping in the hip area is common in the general population. The problematic version, where the snap is accompanied by debilitating pain and weakness, tends to show up in people who perform repetitive hip flexion at extreme ranges, such as ballet dancers and hurdlers.² If you are doing leg raises as part of a standard core workout and the pop is painless, the odds strongly favor this benign tendon-gliding explanation.

Why Leg Raises Are Particularly Prone to Causing Pops

Leg raises are deceptively demanding on the lower back and pelvis. When you lie flat and lift both legs, the weight of your legs acts as a long lever that pulls on the pelvis through the hip flexors. If your abdominal muscles are not strong enough to counteract that pull, the pelvis tips forward into what is called an anterior tilt.³ This sudden tilting can shift the alignment of the lower spine, causing facet joints to gap slightly and release gas, or allowing tendons to slide into positions where they snap.

Research on abdominal training has flagged bilateral straight leg raises as a movement that can compound imbalances around the hip and pelvis, noting that the exercise can both hyperextend and hyperflex the lumbar spine.⁴ In other words, the lumbar spine gets pushed through competing ranges of motion during the same rep. That mechanical tug-of-war is precisely the kind of environment where joints pop and tendons catch.

The psoas muscle, which is the deeper half of the iliopsoas, adds another wrinkle. Its fibers attach directly to the lumbar vertebrae, and when it contracts forcefully it tends to pull the lower spine into a deeper arch while simultaneously compressing the spinal segments. Those compression forces and the arching motion together can encourage audible joint noises in the lumbar facets.⁵ If your lower back pops mainly during the lowering phase of the leg raise, when the psoas is fighting against gravity to control the descent, this mechanism is a strong candidate.

Gas Release in the Facet Joints

The second common explanation for lower back popping during any movement is cavitation, the same phenomenon responsible for cracking knuckles. The small paired joints along the back of the spine, called facet joints, are encased in capsules filled with synovial fluid. When a joint is moved through a certain range or gapped slightly, dissolved gas in the fluid can form a bubble and collapse with an audible pop. This is painless and does not damage the joint.

During leg raises, your lumbar spine transitions rapidly from a more neutral or slightly flexed position into extension as the hip flexors pull the pelvis forward. That quick change in spinal curvature can gap the facet joints just enough to trigger cavitation. You will usually notice that you can pop the joint once but then the sound disappears for a while. That refractory period, typically around 20 minutes, is a signature of gas-release popping and helps distinguish it from tendon snapping, which tends to happen on every rep.

When the Pop Might Signal Something Else

Most back and hip popping is noise without consequence, but a few situations warrant closer attention. If the pop is consistently accompanied by a sharp, catching pain in the front of the hip or groin, a labral tear is one possibility worth ruling out. The labrum is a ring of cartilage that lines the hip socket, and tears in it often produce clicking and locking sensations alongside pain.⁶ Leg raises can aggravate a damaged labrum because the movement loads the hip joint while the ball is pressing into the socket’s front rim.

Athletes with structural hip issues, such as femoroacetabular impingement, sometimes develop compensatory stress patterns that radiate into the sacroiliac joint and the lumbosacral spine. When the hip joint itself cannot achieve the range of motion that a movement demands, the pelvis and lower spine pick up the slack, and that compensatory motion can produce popping or clicking in areas that are absorbing forces they were not designed to handle.⁷

A useful rule of thumb: if the popping is painless, consistent in location, and does not worsen over weeks of training, it is almost certainly mechanical and benign. If it is painful, if the pain is increasing, if you feel weakness in the hip or leg, or if the joint feels like it catches or locks, those are signals that a clinician should evaluate it. Snapping hip syndrome itself is often asymptomatic, but it can become painful in some individuals over time.⁸

How Core Stability Affects the Noise

Your trunk muscles play a direct role in whether your lower back pops during leg raises. When the deep abdominal muscles fire properly before and during the movement, they stiffen the lumbar spine and hold the pelvis in a more neutral position. This stabilization happens partly through increased intra-abdominal pressure, which acts like an internal brace around the spine. Research on spinal biomechanics has shown that this pressure provides a non-direction-specific boost to lumbar stiffness, meaning it helps resist unwanted movement in any plane.⁹

Both increased muscle co-contraction around the trunk and increased intra-abdominal pressure independently improve spinal stability, and the effect is even stronger when both are working together.¹⁰ When that stabilization system falls short, either because the abs are weak or because they fail to engage in time, the pelvis tilts, the spine arches, and the conditions for popping emerge. The trunk-stabilizing muscles normally activate before the limbs move during any exertion.¹¹ If that anticipatory activation is delayed or insufficient, the spine is essentially unsupported for the first fraction of each rep, which is when many people hear the pop.

This explains a pattern many gym-goers notice: the popping tends to happen early in a set or during the first set of the session, and it sometimes diminishes as the muscles warm up and begin activating more reliably. It also explains why the pop may get worse when you are fatigued at the end of a workout, when the stabilizers are too tired to do their job.

Practical Ways to Reduce or Eliminate the Pop

If the popping bothers you or if you want to make the exercise safer for your lower back, several adjustments can help.

• Flatten your lower back first: Before lifting your legs, consciously press your lower back into the floor or bench by engaging your abs and tucking your pelvis slightly. This posterior pelvic tilt reduces the arch that the hip flexors want to create, limiting the conditions that cause both tendon snapping and facet joint gapping.
• Bend the knees slightly: Performing leg raises with a small bend in the knees shortens the lever arm, which reduces the pulling force on your pelvis. Less pull means less pelvic tilt, less lumbar extension, and less opportunity for the iliopsoas to snap. The exercise still targets your abs effectively.
• Lower one leg at a time: Alternating single-leg raises cut the load on the hip flexors and lumbar spine roughly in half compared to bilateral raises. Since the bilateral version has been specifically flagged for compounding hip muscle imbalances, switching to alternating raises is a straightforward risk reduction.⁴
• Stretch the hip flexors: A tight iliopsoas is more likely to catch on bony prominences. In one case study, a recreational athlete with painful iliopsoas snapping resolved the issue entirely with a four-week stretching program and remained symptom-free at six months.¹² A daily hip flexor stretch, such as a kneeling lunge stretch held for 30 seconds per side, is a low-effort habit that can make a noticeable difference.
• Build core strength progressively: If weak abs are allowing your pelvis to tilt during leg raises, the fix is not to grind through more leg raises. Start with exercises that keep the spine more stable, like dead bugs or reverse crunches, and work up to full leg raises as your stabilizers catch up to the demand.

Placing your hands under your lower back or sacrum is a common workaround that provides a tactile cue for maintaining pelvic position. Some people find this eliminates the pop immediately, which supports the idea that pelvic tilt is the primary trigger for their particular noise.

External Versus Internal Snapping

If you have ruled out gas release and suspect the pop is coming from a tendon, it helps to know that snapping hip syndrome has two main external varieties. The external type involves the iliotibial band rolling over the bony bump on the outer hip. This tends to produce a snap felt on the side of the hip and is more associated with walking, running, or side-lying movements than with leg raises. The internal type involves the iliopsoas tendon catching on the front of the pelvis or hip joint, and this is the one most closely tied to hip-flexion-heavy exercises like leg raises.¹

You can sometimes tell the two apart by where you feel the snap. External snapping is on the side of the hip, and you or someone else can often see the band rolling over the bone. Internal snapping is deeper, felt in the groin or low abdomen, and the snap may not be visible from the outside. Internal iliopsoas snapping can also mimic problems inside the hip joint itself, which is one reason clinicians sometimes use imaging to pin down the source.¹ For most people doing leg raises, the internal iliopsoas snap is the overwhelming favorite.

The Role of Flexibility and Warm-Up

Individual flexibility influences how the lower back and hip behave under load. Stiffer hamstrings, for instance, restrict pelvic motion during flexion tasks, which can shift more movement demand onto the lumbar spine. Research has found that less flexible individuals tend to show different patterns of lumbar muscle activation, with the interaction between flexibility and joint angle affecting when and how the back muscles relax and engage during flexion movements.¹³ If your hamstrings are tight, your pelvis has less freedom to tilt naturally, and the lumbar spine may compensate with abrupt positional shifts that produce pops.

Warming up before jumping into leg raises helps on two fronts. First, it increases blood flow to the iliopsoas and surrounding tissues, making them glide more smoothly. Second, it primes the neuromuscular system so that the deep stabilizers fire on time. A few minutes of hip circles, bodyweight squats, and gentle hip flexor stretches before your core work can meaningfully reduce the frequency of popping.

Why the Sound Often Gets Worse Over Time and Then Improves

Many people notice a pattern over months of training: the popping starts when they first add leg raises to their routine, gets more frequent as they increase volume or intensity, and then gradually fades as they get stronger. This arc makes sense when you consider the underlying mechanics. Early on, the core is not strong enough to stabilize the pelvis, so every rep creates conditions for popping. As training volume increases, the hip flexors tighten further from overuse, making tendon snapping more likely. Eventually, core strength catches up, the hip flexors adapt, and the pelvic control improves enough that the spine stays stable and the tendons glide more smoothly.

If you are in the phase where the popping is increasing, that is not necessarily a reason to stop doing leg raises. It is a reason to pay attention to technique, add hip flexor stretching, and consider whether you are progressing the exercise faster than your stabilizers can handle. Backing off to a bent-knee variation for a few weeks while emphasizing anti-extension core work can reset the trajectory without abandoning the movement altogether.

People who use lumbar support devices like belts sometimes report that the popping decreases during belt-assisted sets. This aligns with research showing that external abdominal pressure support increases intra-abdominal pressure and improves spinal stability during dynamic movements.¹¹ The belt essentially does some of the stabilizing work that the abs should be doing, preventing the pelvic tilt and spinal movement that lead to pops. That said, relying on a belt for core exercises somewhat defeats the purpose of training the core in the first place. It is better used as a temporary tool while building the intrinsic stability to manage the movement unassisted.