Iliotibial band

Function

Where it runs and how it is anchored

A review describes the iliotibial band as tough, fibrous fascia running from the iliac crest to the outer upper tibia (shinbone)². It ends on Gerdy’s tubercle, a small bump on the outer front of the upper tibia⁵. Near the hip it splits into a surface layer and a deep layer¹. These enclose the tensor fasciae latae (a small muscle at the upper outer thigh) and anchor it to the iliac crest^1,6. The band receives most of the tendon of the gluteus maximus, the large muscle of the buttock¹.

In 20 embalmed cadavers, the band was firmly attached along the linea aspera, a long ridge down the back of the femur (thigh bone)⁷. That attachment ran from the greater trochanter (the bony bump at the outer hip) down to the outer condyle at the knee⁷. A condyle is a rounded knob at the end of a bone, where it meets another bone at a joint. Cadaver dissections also show it anchored to the femur shaft by the lateral intermuscular septum, a sheet of tissue between muscle groups¹. They show it continuous with the patellar retinacula, bands of tissue at the sides of the kneecap¹.

In 15 cadavers, fibrous strands anchored the lower band to the lower femur¹. These strands split the band into an upper “tendinous” part and a lower “ligamentous” part¹. Only the lower part crosses the knee¹.

Where the lower end attaches

A review says all authors agree the band attaches to Gerdy’s tubercle². It lists four other lower attachments that are often described²:

• a shared attachment with a ligament the review calls the femoral tibial ligament²
• the lower femur above the condyle, through the distal Kaplan fibres (fibrous bands that tie the lower iliotibial band to the thigh bone)²
• along the linea aspera, through the proximal Kaplan fibres²
• the patella (kneecap)²

A review describes the Kaplan fibres as fine fibrous bands running from the band to the septum and lower femur⁸. In 10 cadaver knees, they formed two separate bundles⁹. These fixed to the femur about 54 mm and 31 mm above its lateral epicondyle⁹. That is the outer bony bump at the knee end of the thigh bone.

The band’s size varies a lot between people². A review reports that, for its thickness and width, the usual spread between people is 19% to 68% of the average². Some authors argue it should not count as a separate structure at all². Their reason is that its edges cannot be clearly told apart from the rest of the fascia lata in dissection².

What it does at the hip and knee

The band is thought to act as a strut in walking, steadying both hip and knee, mainly against side-to-side movement². Through the band, the tensor fasciae latae generally pulls forward and up to bend the hip². The gluteus maximus pulls backward to straighten it².

In a review of cadaver work, all 6 cutting studies reported the band backing up the anterior cruciate ligament against inward rotation³. In a straight knee without an ACL, its attachments do nothing to stop the tibia sliding forward². Once the knee bends past 30 degrees, they reduce that slide². One study found the Kaplan fibres provided about 44% of the resistance to inward rotation at 90 degrees of bend, with the ACL aside⁸. The band’s attachments to the kneecap steady it against slipping out inward².

How it stretches and stores energy

Tests of dissected bands put its Young’s modulus (how stiff a material is in itself) at about half that of the Achilles tendon². In 10 unembalmed bands pulled until they failed, the average peak load was about 873 newtons (a unit of force), at 9% stretch¹⁰.

In a moderately paced run, a computer model put the band’s stored energy at up to 5% of the run’s positive work². That is about 14% of what the Achilles tendon adds². Models built from dissections compared walking on two legs¹¹. They estimated the human band stores 15 to 20 times more elastic energy than the chimpanzee’s, per unit of body mass and stride¹¹.

Shear wave elastography (an ultrasound method that estimates how stiff a tissue is) was done in single-leg standing². Band stiffness rose with hip adduction (moving the thigh toward the midline) and fell with slight hip abduction². In 30 adults, 10 degrees of hip adduction raised band stiffness at mid-thigh and near the knee, while tensor fasciae latae stiffness did not rise¹².

Breakdown

Iliotibial band syndrome

Runners and cyclists commonly get iliotibial band syndrome, an overuse injury¹. A systematic review estimated its incidence (how many new cases appear in a group over a set time) in runners at 5% to 14%⁴. Another systematic review calls iliotibial band syndrome the second most common running injury, making up about a tenth of running injuries¹³.

Friction or pressure

A review says the syndrome was long thought of as a friction injury². Pressure on the nerve-rich fat between the band and bone is now proposed instead². One anatomy study concluded the band cannot roll over the epicondyle, because it is anchored to the femur¹. The authors suggest the movement seen comes from tension shifting between its front and back fibres as the knee bends¹.

In the MRI (a scan that shows soft tissue in detail) part of that study, six volunteers were scanned¹. At 30 degrees of knee bend, the band pressed against the outer epicondyle of the femur as the tibia turned inward¹. With the knee straight, it moved outward¹. A review adds that MRI shows the tissues under the lower band squeezed as the band tightens².

In cadaver dissections, the fat between the band and the femur was rich in blood vessels and nerves¹. In some specimens it held Pacinian corpuscles, nerve endings that sense pressure¹. In two runners with recent-onset iliotibial band syndrome, MRI changes were in this fat, not in the band¹. On anatomical grounds, the authors suggest overuse injury may be linked more to pressure on the fat than to rubbing¹.

How running loads it

A model built partly from a study of nine runners with the syndrome puts impingement of the band near footstrike¹⁶. Those runners’ knees were bent an average of 21.4 degrees at footstrike¹⁶. The same authors propose that downhill running raises the risk because the knee is straighter at footstrike¹⁶. They also propose sprinting is less likely to make it worse¹⁶.

One prospective study (a study that follows people forward in time) followed female runners¹⁷. Those who later had the syndrome showed a higher modelled strain rate, how fast the band stretches, than uninjured runners¹⁷. The authors suggest the rate of stretch, rather than its size, may be a cause¹⁷.

A second prospective study followed female recreational runners for two years¹⁸. The 18 who developed the syndrome had shown more hip adduction and inward knee turning when running¹⁸.

A systematic review looked at 13 studies, one of them prospective¹³. Female runners who went on to get the syndrome showed more peak hip adduction and inward knee turning during stance¹³. Another systematic review found limited or conflicting evidence on the causes in runners⁴. It was unclear whether weak hip abductors play a major role⁴.

Other injuries

On MRI after ACL rupture, reported rates of Kaplan fibre injury range from 6.4% to 61%⁸.

Higher up, a 2013 imaging review describes injuries of the upper band as an under-recognised source of hip pain¹⁹. Tendinopathy (local tendon pain with activities that load it) at the band’s origin is described as a possibly overlooked cause of front outer hip pain²⁰.

Recovery

How the Kaplan fibres heal

A review reports fewer Kaplan fibre injuries in people scanned more than 90 days after ACL rupture⁸. It reads this as a possible sign of healing over time⁸. A case series (a report on a group of patients with the same condition, without a comparison group) looked at 89 people with ACL injury²¹. Kaplan fibre injury was seen in 30.3%²¹. Nine months after ACL reconstruction (surgery to rebuild the ligament), MRI showed the fibres rejoined in 14 of the 27 injured (51.9%)²¹.

What stretching does to the band

From pull tests on 10 unembalmed bands, the authors conclude the band can withstand a lot of tension¹⁰. They add that stretching forces used in clinics likely stay within its elastic range, without lasting lengthening¹⁰. A 2022 review argues that stretching now and then is unlikely to change the band’s length or mechanical properties²². One randomised trial (a study that assigns people to groups by chance) had 30 adults¹². One session of stretching or foam rolling did not change band stiffness¹².

How the band changes over time

In 14 recreational runners with the syndrome, band stiffness was higher after 6 weeks of care than at the start²³. Their pain and function improved over the same time²³.

In 33 donors aged 4 months to 93 years, the band’s tensile properties did not depend on age, apart from maximum strain in males²⁴.

Connections

Bones and muscles

The band links the iliac crest of the pelvis with the tibia². In six dissected cadavers, the gluteus maximus had a large insertion into the fascia lata²⁵. The authors suggest the iliotibial tract could count as one of its tendons²⁵. The tensor fasciae latae sits in the upper outer front of the thigh, between the band’s surface and deep fibres⁶. It helps steady the outer knee by pulling the band taut²⁶.

The outer knee

In cadaver work, the band steadies the outer knee together with three partners². These are the fibular (outer) collateral ligament, the biceps femoris (a hamstring) and the tendon of the popliteus (a small muscle behind the knee)². The knee kept its passive stability as long as at least two of these were intact². The popliteus tendon lies deep to the lateral collateral ligament, and the band’s surface layer lies over it²⁷.

Related pages

Related exercise pages: side-lying hip abduction, where hip position is the link²⁸. In 18 unfixed cadavers and 12 people having hip replacement, force under the band at the greater trochanter rose with adduction and fell with abduction²⁸. That study did not test the exercise itself²⁸. A separate page covers the standing IT band stretch.

Sources

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Every source the library cites

Changes

• October 22, 2026 Links to the new standing IT band stretch page
• September 30, 2026 A supporting claim was narrowed to match its source; the page text is unchanged.