Groin, buttock or outside: where it hurts tells you which structure it is

TELLING THEM APART / HIP, SI JOINT OR LUMBAR SPINE

Where it hurts is the most useful clue. Groin pain points to the hip joint. Buttock pain points to the sacroiliac joint or the low back (lumbar referral). Pain on the outside of the hip points to the gluteal tendons. Pain past the knee with numbness or tingling points to a lumbar nerve root. Hip joint, sacroiliac joint and lumbar spine problems are commonly present at once in the same person.

All three cause pain in overlapping areas. Sorting them out is the difference between one treatment that works and three that do not.

How do I know if my pain is from my hip or my back?

• Groin — the hip joint, until proven otherwise. Hip problems send pain to the groin and the front of the thigh. Patients often show it by cupping the side of the hip with the thumb in the groin.
• Buttock — sacroiliac joint or lumbar referral. The SI joint sends pain below the L5 spinous process (the bony bump at the base of the spine). It hurts over the joint itself and into the back of the thigh.
• Outside of the hip, sore to lie on — gluteal tendons, not the joint and not the spine. This is the most often misdiagnosed of the three.
• Down the leg past the knee, with numbness or tingling — lumbar nerve root.

That map is not perfect. But it sorts out more cases than any scan does.

What are the signs that pain is coming from the hip joint?

• Groin pain, and loss of inward (internal) rotation on exam — the earliest and most reliable sign
• Pain on rising from a chair and putting on shoes and socks
• Deep, aching, sometimes spreading to the knee — a hip problem showing up as knee pain is common and catches people out
• No neurological findings

What does sacroiliac joint pain feel like?

• Pain centered below the belt line, over the joint, often pointed to with one finger
• Worse with long standing, stair climbing, and rolling over in bed
• Often after a lumbar fusion — a fused segment shifts load here, and this is routinely missed because everyone is still watching the fusion
• Several provocation tests positive on exam, which tells more than any one of them

How can I tell if my hip pain is coming from my lower back?

• Pain that changes with spine position — worse bending back (extension) suggests facet, worse bending forward (flexion) and sitting suggests disc
• Pain running past the knee, with numbness in a nerve’s skin area (dermatomal) or weakness in its muscles (myotomal)
• Morning stiffness in the back itself
• Brought on by spine movement while the hip stays still

Why all three so often coexist

Because they are mechanically linked, and they share a terrain.

Mechanically: a stiff hip forces the pelvis and low back to make up the range the hip no longer gives. That loads the SI joint and the facets. Weak abductors (the side hip muscles) let the pelvis drop with each step, and that lopsided motion travels upward. Fuse a lumbar segment and the SI joint absorbs what that segment used to move.

Biologically: hip cartilage, the SI joint and the facet joints are all synovial tissue (joint-lining tissue) answering to the same body-wide environment. Adipose-derived inflammatory signaling (inflammation signals from fat tissue) reaches all of them through the blood, no matter the load. That is why metabolic syndrome tracks with osteoarthritis in joints that never carried unusual weight. Insulin resistance weakens cartilage cells (chondrocytes) and stiffens collagen through glycation everywhere at once.

And the social driver: a job that keeps you seated for nine hours weakens the glute muscles. It shortens the hip flexors. It takes away the small daily movement that keeps all three structures tolerant. Then the weekend asks them to perform. That is not a failure of discipline. It is a workstation and a commute.

Why guessing is expensive

Three structures, three different treatments. And imaging will find degenerative change in all three in most people past fifty. Treat the one the scan described loudest and you have a one-in-three chance of aiming at the right thing.

This is where symptom-based silos do their damage. The hip goes to one clinician and the spine to another. Nobody is paid to answer which one is causing the pain today. The patient pays for that gap, usually across several procedures.

How we settle it

• An exam that isolates each structure — hip range with the spine still, spine movement with the hip still, and SI provocation tests as a group.
• A neurological screen, which settles the nerve root (radicular) question quickly.
• Imaging read next to the exam, never in place of it.
• A diagnostic block where it is still truly unclear. Numb one structure. If the pain goes, you have your answer. That is the rule across this site — a block confirms the structure, and then we treat it.
• A metabolic panel, because three joints failing together is a signal about the terrain, not three coincidences.

If leg symptoms suggest a nerve, an EMG nerve test of the leg helps sort the back from the hip.

Frequently asked questions

My pain is on the outside of my hip. Which is it?

Almost always the gluteal tendons rather than the joint or the spine. Gluteal tendinopathy.

Can hip arthritis cause knee pain?

Yes, and it catches people out often. Hip osteoarthritis.

Why did my SI joint start hurting after a fusion?

The fused segment shifts load to it. Very common and often missed. After spine surgery.

Do I need an MRI first?

Often not. An exam plus a diagnostic block answers more than a scan does here. How we assess.

Is my lower back pain actually my hip?

It can be. Hip joint pain usually sits in the groin and the front of the thigh. It is worst getting up from a chair or putting on socks. On exam it shows up as lost inward rotation. A stiff hip also forces the pelvis and lower back to make up the missing motion. That loads the SI joint and the facet joints, so a hip problem often ends up hurting the back too.

Is there a simple test I can do at home for hip versus back pain?

A few quick checks help. Point with one finger to the worst spot. Groin says hip. Beside the tailbone says SI joint. The outer bony point you cannot lie on says gluteal tendon. Central low back says spine. Cross the painful leg over the other knee while seated; groin pain points to the hip. If leaning backward brings on central back pain, that points to the facets.

Why do my hip, SI joint and lower back all hurt at once?

Because they are linked mechanically and share the same body chemistry. A stiff hip pushes extra work onto the pelvis and spine. Weak hip muscles let the pelvis drop with each step. All three are joints lined with the same kind of tissue, so inflammation from fat tissue and insulin resistance reach them at once. On top of that, long days sitting weaken the glutes and tighten the hip flexors.

What happens if the first treatment was aimed at the wrong structure?

We find out at the follow-up and we say so. A treatment aimed at a structure that was not causing the pain produces no change. No change is useful information. The plan then changes rather than repeats. Repeating the same treatment that did nothing, without going back to the diagnosis, is the most common pattern we see in people who come here. It is not a plan.

Related reading

• Hip osteoarthritis
• Gluteal tendinopathy
• Spine and sacroiliac joint
• Shoulder or neck?

A short self-check before you book

It will not replace an exam, but it will tell you which page to read next.

• Point with one finger to the worst spot. Groin says hip. A spot below the belt line beside the tailbone says sacroiliac. The bony point on the outside you cannot lie on says gluteal tendon. Central low back says spine.
• Sit down and cross the painful leg over the other knee. Groin pain with that move points at the hip joint.
• Stand on the painful leg alone for thirty seconds. If that brings on buttock pain, it points at the sacroiliac joint or the abductors.
• Lean backward. If that brings on central back pain, it points at the facets. Sit slumped for a minute. If that is worse, it points at the disc.
• Note whether anything goes past the knee, and whether it is numb or tingling as well as painful.

Several of those may bring on the pain. That is truly useful, not a failed test. It means more than one structure is adding to the pain. That is the common case. It changes the order of treatment rather than ruling anything out.

What happens if we get it wrong

We find out at the follow-up, and we say so. A treatment aimed at a structure that was not causing the pain does not fail quietly. It produces no change, and that is information. The plan then changes rather than repeats.

Repeating the same treatment that did nothing, without going back to the diagnosis, is the single most common pattern in the history of the people we see. It is not a plan.