SI Joint Pain When Running: Causes, Tests, Exercises

The pain is not in the middle of your back but off to the side — a thumb's width below the iliac crest, exactly where your thumb lands in a small dimple. It shows up getting out of the car, on stairs and at night when you turn over in bed. During the run itself it is often less severe than afterwards. That is the classic pattern of sacroiliac (SI) joint pain, and the good news is that it is almost always manageable without surgery or giving up sport — just not with the measures most commonly recommended online.

What the sacroiliac joint is — and why running loads it

The sacroiliac joint connects the sacrum to the ilium, and with that the spine to the legs. It is not a freely moving joint like the shoulder or hip but a very stiff connection held by several extremely strong ligament complexes — the strongest in the human body. Actual movement is in the range of two to four millimetres. That tiny range is exactly where most explanatory models fail: a joint that barely moves cannot be mechanically "jammed".

Its job is demanding all the same: the SI joint has to transfer forces from the upper body to the legs and back. When running, ground reaction forces reach two to three times body weight — for a 75-kilogram runner that is 150 to 225 kilograms per step, more than a million steps in a training year. Part of that energy travels through the hip, part through the SI joint. What matters is not the single peak load but whether the surrounding musculature can absorb that load evenly.

The clinical term today is usually "SI joint dysfunction" or "pelvic girdle pain", not inflammation of the joint. Studies attribute roughly 15 to 25 per cent of chronic low back pain to the SI joint; among runners with stubborn gluteal pain the share is similar. This is not an exotic edge case but one of the most common causes of one-sided pain in the pelvic region.

SI joint, disc or hip? The distinction decides

The most important step is not the exercise but the assignment. Three structures produce similar symptoms in the buttock yet need different treatment:

• SI joint: One-sided, pinpoint, directly below the iliac crest (dimple test: the two dimples above the buttocks). Referred into the buttock and the back of the thigh, rarely below the knee. Worse in single-leg stance, on stairs, after prolonged sitting and when turning in bed. Better with walking.
• Lumbar disc: More central or one-sided, often with clear referral past the knee into the foot or toes, plus tingling or numbness. Provoked by coughing, sneezing, straining and bending forward. A herniated disc has its own return-to-running protocol.
• Hip: Pain in the groin, not the buttock. Restricted internal rotation, typically stiff in the morning. Hip pain when running refers forward, not backward.
• Piriformis: Deeper in the buttock, more burning, with point tenderness in the middle of the muscle. Often confused with the SI joint — see piriformis syndrome.

A test you can do at home: sit down and feel for both iliac crests and the dimples above the buttocks. Press with your thumb about one centimetre below and two centimetres to the side of the dimple. If that exact point reproduces a sharp, familiar pain and one leg pulls more in single-leg stance than the other, the likelihood of SI joint involvement is high. That is not a diagnosis but a useful clue — the clinical provocation tests (thigh thrust, Gaenslen, sacral thrust, distraction, compression) are scored as a cluster: three or more positive tests are considered sufficiently specific.

Why it is usually not the joint itself

The idea that a practitioner needs to "put the joint back in" persists because it is intuitively appealing. Anatomically it does not hold: the SI joint is held by a ligament complex that withstands tensile forces of several hundred newtons — a manual impulse cannot durably displace it. What actually happens during such treatment is a neurophysiological response: the abrupt movement alters pain processing in the spinal cord for hours to days, similar to the effect of a saline injection. Short-term relief is real, permanent correction is not.

The robust explanation is different: the SI joint is stabilised by muscles that are too weak in many runners — above all gluteus maximus, gluteus medius and the deep trunk musculature. When that strength is missing, the ligament complex has to carry the shear forces alone. That explains three typical patterns:

• Weak gluteus maximus: The femur rotates and adducts inward on landing, the pelvis drops. The SI joint receives a rotation it is not built for.
• Weak gluteus medius: The pelvis drops towards the swing side in single-leg stance (Trendelenburg sign). Compensating costs strength in the lower back — often on the opposite side from the pain.
• Stiff ankles and hip flexors: When hip and ankle range are missing, the pelvis supplies it. Anyone who cannot reach hip extension compensates with lumbar extension and pelvic rotation.

Add the training factor: one-sided load, a rapid build in volume, a new surface or a shoe change shift the ratio between load and tolerance. The rule from increasing training volume — no more than ten per cent per week — applies more strictly to the pelvis, because bone adapts more slowly than muscle and circulation.

What helps immediately when it is acute

In the acute phase, when pain dominates every movement, the same applies as with most back complaints: movement within tolerable range, no protective posture for days on end. Concretely:

• Walk instead of sit. Sitting increases load on the SI joint and shortens the hip flexors. In an office job: stand and walk for two minutes every 45 minutes, and set seat height so the hips sit slightly above the knees.
• Heat, not ice. With muscular involvement, heat relaxes the gluteal and lumbar muscles that are usually part of the problem. Ice makes sense right after a load in an acute irritable phase, but not as a permanent measure.
• Sleep with a pillow between the knees. In side-lying this prevents the pelvis twisting overnight — the most common cause of the stabbing pain when turning.
• No aggressive stretching. The classic lunge with rotation stretches the ligament complex that is already irritated. It feels good briefly and reinforces the irritation long term.

For training that means: running is allowed as long as it does not worsen symptoms. Reduce pace, shorten the stride slightly and avoid downhills, fast sessions and long runs for now. The pain traffic light is the sober criterion: pain up to 3 out of 10 during the run and back to baseline 24 hours later is tolerable. Anything above that means one step back.

The strength programme: seven exercises, two to three times per week

The decisive intervention is strength, not mobility. A programme that works consistently for pelvic girdle pain in both research and practice has three components: hip extension under load, anti-rotation and single-leg control. All single-leg, because the SI joint carries the most load in single-leg stance.

• Hip thrust: 3 × 10 with a barbell or dumbbell across the pelvis. Hold for two seconds at the top and squeeze the glutes deliberately. The foundational exercise for gluteus maximus.
• Lateral step-up: 3 × 8 per side onto a box at knee height, slowly up and down without momentum. Trains hip extension and pelvic stability at once.
• Single-leg deadlift: 3 × 8 per side with a slightly bent standing leg. The best test of whether the pelvis stays quiet in single-leg stance.
• Side plank: 3 × 25 to 40 seconds per side. Targets the obliques and quadratus lumborum — the main protection against pelvic rotation.
• Anti-rotation press (Pallof press): 3 × 10 per side. Anchor a band at chest height, press forward without letting the torso rotate.
• Lateral band walks: 3 × 12 per direction with a mini band above the knees, in a half squat. Direct work for gluteus medius.
• Copenhagen adductor plank: 3 × 15 to 20 seconds per side (or with brief lifts of the top leg). Adductor strength lowers groin injury risk and stabilises the pelvis from the other side.

The structure: two to three times per week, 25 to 35 minutes, at least 48 hours between sessions. Progress through load and repetitions, not through new exercises — going from 40 to 70 kilograms on the hip thrust gains more than trying ten variations. How strength work fits into a running plan is covered in strength training for runners; in the weekly schedule, strength should never sit directly before a hard session.

Mobility is not a contradiction but a supplement — dosed and dynamic: hip flexor stretch in a lunge without rotation, 2 × 30 seconds after the run, plus ankle mobility at the wall. If you sit a lot you need both. If you train a lot you need strength first.

Common mistakes that prolong the problem

• Stretching as the main measure. An irritated ligament complex responds to stretching with more irritation. Five minutes on a foam roller followed by a 40-minute run is not therapy.
• Treating only the painful side. The pain often sits opposite the weakness. Mobilising only the side that hurts misses the gluteus medius on the other side.
• Insoles as the first solution. Orthotics can help with a relevant leg length difference or foot deformity but do not replace strength. Flat feet when running is a topic of its own.
• Returning to hard sessions too soon. Intervals and downhill running are the most demanding formats for the SI joint. They come back only when single-leg strength works without irritation.
• Painkillers before the run. Anyone running on NSAIDs is ignoring the signal the body sends. Why that is risky is covered in painkillers in endurance sport.

How long it takes — and what a realistic timeline looks like

With consistent strength work, most SI joint complaints improve markedly within four to eight weeks. The first two weeks often bring little visible change because strength adaptation takes time: neuromuscular coordination improves quickly, but increases in muscle cross-section follow only after six to eight weeks. Anyone who gives up after ten days because "nothing is helping" stops in exactly the phase where the effect is built.

A tried framework: weeks 1 to 2, strength twice per week and running volume cut by 30 per cent, no intensity. Weeks 3 to 4, strength twice per week, volume back to normal, first short strides. Weeks 5 to 8, keep the strength work, reintroduce intensity step by step, rebuild longer runs. If pain is unchanged or worse after eight weeks, a medical assessment makes sense — not because something dangerous is likely, but to rule out other causes (hip impingement, inflammatory disease, nerve involvement).

How Peakora handles recurring complaints

Pelvic pain rarely arrives as a single event but as a pattern: two good weeks, then one long run, then three weeks of irritation, then a break. That pattern is visible in the calendar but not in how you feel. Peakora converts every run and every strength session into training stress and puts it on one curve: CTL as accumulated load tolerance, ATL as short-term fatigue, TSB as the difference. When volume rises faster than tolerance, the curve shows it before the pain does. How the three values relate is explained in CTL, ATL and TSB.

In practice that means: a week with symptoms is an input to the plan, not a reason to delete it. The engine recalculates the following weeks without losing sight of the goal — and without measuring you against your old level. If you want to return to structure after a break, the marathon training cluster provides the framework; the basic terms are in the training glossary.

Frequently asked questions