One-Sided Lower Back Pain Near the Hip: Sacroiliac Joint Dysfunction vs Facet Joint Pain vs Kidney Pain

If your pain sits on one side of the lower back, close to the “dimple” area above the buttock or near the top of the hip, you are not alone in feeling unsure about what is causing it. This zone is a crossroads for several structures:

• Sacroiliac joint (sacroiliac joint dysfunction or sacroiliac joint pain): where the spine meets the pelvis; pain often feels deep and close to the back of the hip.
• Lumbar facet joints (facet joint–mediated pain): small joints in the back of the spine that guide motion; pain often flares with certain movements like leaning back or twisting.
• Kidneys (kidney stones or kidney infection): pain can show up as flank or back/side pain and may mimic musculoskeletal pain—especially early on.

The good news: the pattern of pain + what makes it worse + associated symptoms (especially urinary symptoms and fever) usually points you in the right direction.

Use these questions to quickly sort your symptoms into the most likely bucket.

You might be dealing with sacroiliac joint dysfunction if:

• Pain is one-sided and very close to the bony “dimple” area just below the back of your waistline (near the posterior superior iliac spine).
• Pain is often deep in the upper buttock, sometimes felt into the groin or lateral hip, and may occasionally refer into the upper thigh.
• Pain is triggered by transitional movements: standing up from sitting, getting out of a car, rolling in bed, climbing stairs, taking long strides.

Facet joint pain is more likely if:

• Pain is on one side of the spine, often slightly above the beltline, and may spread to the buttock or upper thigh but usually stays “mechanical” (movement-related).
• Pain worsens with back extension (arching backward), standing/walking downhill, or twisting/rotation.
• You feel morning stiffness or stiffness after sitting still, and it eases as you loosen up.

Kidney-related pain becomes more likely if your back/side pain comes with:

• Blood in urine, urinary urgency, burning with urination, or cloudy/foul-smelling urine.
• Fever or chills, nausea/vomiting, and you feel systemically unwell (this is especially concerning for kidney infection).
• Pain that sits more in the flank (back/side below the ribs) and may come in waves (common with kidney stones).

If kidney infection is possible, treat it as urgent—kidney infection symptoms commonly include fever/chills, urinary symptoms, nausea/vomiting, and back/side/groin pain.

A practical clinical clue is whether you can point with one finger to a spot very close to the posterior superior iliac spine (the dimple area). This is commonly described in clinical evaluation of sacroiliac joint dysfunction.

People often report pain with:

• Standing from sitting, sitting down, getting out of a car
• Rolling in bed
• Stairs, lunges, long strides
• Prolonged standing with weight shifted to one leg

Sacroiliac joint pain can be associated with events or states that stress the pelvis:

• Pregnancy/postpartum changes
• Falls/trauma onto the buttock
• Repetitive loading (certain sports or jobs)
• Prior spine surgery or altered gait mechanics

These are pattern checks, not definitive tests.

1. Single-leg stance check: does standing on the painful-side leg increase the deep buttock/hip-back pain quickly?
2. Step-up or stair check: do stairs or stepping into a car reproduce the pain sharply?
3. Transition check: is it worse when you change positions than when you maintain a position?

If these ring true, sacroiliac joint dysfunction stays high on the list. For a formal diagnosis, clinicians often use a combination of history, exam maneuvers, and (when needed) image-guided diagnostic injections.

Facet joint–mediated pain often flares with:

• Leaning backward (extension)
• Twisting (rotation), especially combined with extension
• Prolonged standing or walking with an “arched” posture

Facet pain is often described as axial low back pain (centered in the back) but can refer into:

• Buttock
• Hip region
• Upper thigh (commonly not below the knee)

Why facet pain can be stubborn

Facet joints are small but highly innervated. Irritation from arthritis-like changes, overload, or repetitive extension/rotation can keep the joint sensitive. Reviews describe typical patterns like morning stiffness and provocation with extension/rotation.

How clinicians confirm it:

No single symptom proves facet pain. When it is strongly suspected and symptoms persist, clinicians may consider diagnostic blocks (for example, anesthetizing the medial branch nerves that supply the facet joints) as part of an interventional diagnosis-and-treatment pathway.

Kidney pain is often misunderstood because it can feel “deep” and can show up in the back/side area.

Kidney stone symptoms commonly include:

• Sharp pain in the back/side (flank) that may radiate to lower abdomen or groin
• Pain that can come in waves
• Blood in urine (pink, red, or brown)
• Urinary urgency, pain with urination, cloudy or bad-smelling urine

Nausea and vomiting may occur, especially with severe pain.

Kidney infection symptoms can include:

• Fever and chills
• Pain in the back/side/groin
• Burning with urination, frequent urge to urinate
• Nausea and vomiting
• Cloudy, foul-smelling urine; sometimes blood or pus in urine

Clinically, flank pain with urinary symptoms and fever/nausea should raise concern for kidney infection.

A key difference: motion usually doesn’t “mechanically” reproduce kidney pain

Mechanical pain (sacroiliac joint dysfunction or facet joint pain) typically changes noticeably with posture, bending, twisting, or position transitions. Kidney pain may not follow that pattern and is more likely to come with urinary symptoms or systemic symptoms (fever, chills, nausea).

Try describing your pain using these location anchors:

• Sacroiliac joint dysfunction: one-sided pain near the posterior superior iliac spine (dimple area), deep buttock, sometimes groin/lateral hip.
• Facet joint pain: one-sided low back pain closer to the spine, worse with leaning back/twisting; may refer to buttock/upper thigh.
• Kidney stones/infection: flank pain (back/side under ribs), may radiate toward groin; often accompanied by urinary changes, and infection adds fever/chills.

Seek urgent medical care (same day/emergency) if you have one-sided back pain near the hip plus any of the following:

• Fever, chills, or feeling acutely ill (possible kidney infection or other infection).
• Blood in urine, inability to urinate, severe colicky flank pain (possible kidney stone complication).
• New bowel or bladder dysfunction, saddle numbness, or progressive leg weakness (possible cauda equina or spinal emergency).
• Unexplained weight loss, night pain/rest pain, history of cancer, or immunosuppression with new back pain (needs prompt evaluation).

If your symptoms look mechanical (sacroiliac joint dysfunction or facet joint pain) and you have no red flags:

• Relative rest: avoid the specific triggers (deep twisting, heavy lifting, long car rides without breaks).
• Heat or ice: choose what feels better.
• Gentle walking: often better than prolonged bed rest for mechanical low back pain.

If it feels like sacroiliac joint dysfunction:

• Avoid long strides and uneven loading (for example, standing with weight on one leg).
• Use a pillow between knees when sleeping on your side to reduce pelvic torque.

If it feels like facet joint pain:

• Reduce repeated extension (excessive arching backward).
• Break up long standing with brief sitting or gentle flexion-based stretches if they help.

If symptoms are not improving, a clinician may evaluate you and decide whether targeted physical therapy, medication, or further work-up is appropriate.

Many people assume they need a scan immediately. In reality, major guidelines emphasize that early imaging is often unnecessary for uncomplicated low back pain—unless red flags are present or symptoms persist despite conservative care.

A practical, evidence-based approach is:

• No immediate imaging for most uncomplicated low back pain.
• Imaging is considered if red flags exist or if you have persistent symptoms after a period of appropriate conservative management.

For suspected kidney causes, testing is different: urine testing and other evaluation is often central when urinary symptoms or fever are present.

Use these clues when you are stuck between sacroiliac joint dysfunction, facet joint pain, and kidney pain.

If your pain is worst during transitions

Standing up, getting out of a car, rolling in bed strongly favors sacroiliac joint dysfunction.

If your pain spikes when you arch backward or twist

This strongly favors facet joint pain.

If you have urinary changes or blood in urine

This strongly suggests kidney stones or urinary tract involvement rather than a joint.

If you have fever/chills and feel sick

This is a major warning sign for kidney infection, especially when paired with urinary symptoms and flank/back pain.

A typical evaluation may include:

• History: exact pain location, triggers, urinary symptoms, fever, nausea/vomiting.
• Physical examination: movement testing; palpation; neurologic screen; maneuvers that stress the pelvis or spine.
• If kidney cause is suspected: urinalysis and other tests as appropriate.
• If facet joint pain is suspected and persistent: interventional diagnostic blocks may be considered in some care pathways.
• If sacroiliac joint dysfunction is suspected and persistent: a structured exam plus confirmatory approaches (including image-guided injection in select cases) may be used.

Schedule an appointment soon if:

• Pain is still significant after 1–2 weeks of sensible self-care
• Pain keeps recurring on the same side
• You cannot return to normal activities
• Pain is accompanied by new numbness, weakness, or spreading leg symptoms
• You are unsure whether symptoms could be kidney-related (especially if urinary symptoms appear)

If you remember only a few things, remember these:

1. Mechanical triggers help you separate joints from kidneys.
   • Transitions → sacroiliac joint dysfunction
   • Extension/twist → facet joint pain
2. Urinary symptoms and systemic illness should push kidney causes to the top.
   • Blood in urine, colicky flank pain → kidney stones
   • Fever/chills + urinary symptoms + flank/back pain → kidney infection
3. Red flags change the plan immediately. Neurologic emergency symptoms, fever, weight loss, cancer history, or severe urinary problems warrant urgent evaluation.

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