What Is STIR on an MRI Report?

Plain-language definition

STIR stands for short tau inversion recovery. It's a T2-like MRI sequence that suppresses the signal from fat. Because fat is bright on most basic MRI sequences — and because many subtle injuries also produce a bright signal — the bright fat can mask the abnormality. STIR knocks the fat signal down to near-black so that anything water-rich (a bone bruise, edema, inflammation, a small fluid collection) shines out against a dark background.

It's the sequence of choice when a radiologist needs maximum sensitivity to fluid or edema, especially in bone and around tendons.

Why it matters

STIR is the sequence most often used to detect:

• Bone marrow edema. A stress reaction or stress fracture that may not appear on X-ray will glow brightly on STIR.
• Occult fractures. Hairline fractures in the hip, sacrum, scaphoid wrist bone, or vertebral body can be invisible on plain film and on basic T1/T2 images, but unmistakable on STIR.
• Tendinitis and tenosynovitis. Inflammation around a tendon stands out as bright signal against the suppressed fat background.
• Soft-tissue contusions and muscle strains. Subtle edema following an injury is much easier to see on STIR than on a standard T2.
• Bone metastases and marrow infiltration. Some cancers replace normal marrow with cellular tissue that stands out on STIR.

Your report may refer to STIR with language like "increased STIR signal within the medial femoral condyle, consistent with a bone bruise" or "no abnormal STIR signal."

How STIR shows up in a Precise Imaging context

Most musculoskeletal MRI protocols at Precise — knee, ankle, hip, shoulder, spine — include a STIR sequence as part of the standard exam. It's particularly common in trauma and sports injury referrals where the question is "is there a bone bruise or hidden fracture?"

STIR is also routinely included in spine MRIs when the radiologist is looking for marrow edema (e.g. in suspected compression fractures or active spondyloarthritis). You don't need to do anything different to get a STIR sequence — the technologist runs it as part of the standard protocol.

STIR vs. fat-saturated T2

Both techniques suppress fat, but they get there differently. STIR uses a timing-based suppression that works reliably even on lower-field magnets or in areas where the magnetic field is uneven. Fat-saturated T2 uses a frequency-selective pulse that gives sharper images but can fail in areas of uneven magnetic field, like around metal hardware. Radiologists pick between them based on the body part and protocol.

Disclaimer

This explainer is general patient education and does not replace personalized interpretation by your ordering provider and the reading radiologist. The clinical meaning of any STIR finding depends on the context of your injury, symptoms, and other imaging.

Frequently asked questions

Why is STIR used for bone bruises?

A bone bruise is microscopic bleeding and edema inside the bone marrow. The bright marrow fat normally hides that edema on standard T2. STIR suppresses the fat, so the edema becomes the brightest thing in the picture — easy to spot.

Does STIR require contrast?

No. STIR is a non-contrast sequence.

Can STIR detect a stress fracture before an X-ray?

Yes. A stress reaction or early stress fracture often shows up on STIR days or weeks before any change is visible on plain X-ray. For a high-suspicion clinical picture, MRI with STIR is often the first-line test.

Will STIR pick up cancer in the bone?

Many bone metastases and marrow infiltration patterns are visible on STIR because they replace normal fatty marrow with cellular tissue. STIR is not a screening test for cancer, but it adds important information when used in a problem-focused MRI.

Is STIR safe?

Yes. Like all MRI sequences, STIR uses the same magnetic field and radio-frequency pulses — no radiation and no contrast required.