Radiology glossary

Bone Bruise — What It Means on Your Report

Part of: General orthopedic findings, explained

Full explainer: Bone Bruise — What It Means on Your Report

The MRI shows a bruise-like signal inside the bone — the deep, invisible counterpart of a skin bruise. When bones collide or absorb a hard impact — the knee twisting in a sports injury, a fall onto the hip, a blow to the shin — the bone's rigid outer shell may stay intact while the spongy marrow inside suffers microdamage and bleeding. X-rays look completely normal, because the cortex never cracked; only MRI's sensitivity to water reveals the edema-like signal blooming in the marrow. Radiologists sometimes classify them by depth, from signal confined near the surface to changes reaching deep into the bone. A bone bruise is more than trivia: its pattern is a footprint of the injury mechanism — the classic paired bruises of an ACL tear, for example, tell the story of how the knee twisted — and it marks the bone as needing time. Most bone bruises fade over six to twelve weeks as the marrow heals, though deeper ones linger longer. The finding says “this bone took a hit”; your doctor reads how hard and what else was injured with it.

What it means on CT

CT cannot show a bone bruise — the marrow edema is invisible at CT density resolution, and the intact cortex looks entirely normal. CT may show the fracture that a bone bruise accompanies, but the bruise itself is beyond it. A normal CT never rules out a bone bruise; only MRI can. CT may still be ordered after significant trauma to map the bones in fine detail and exclude an occult fracture — a reasonable step when the mechanism was forceful. But a normal CT does not exclude a marrow injury, because the bruise lives below CT’s resolution. The two tests answer different questions: CT asks ‘is anything broken?’, MRI asks ‘is the marrow injured?’

What radiologists look at next

For a bone bruise, the radiologist maps the marrow signal abnormality in three dimensions: which bone, what region, how extensive, and how deep the signal extends from the surface — depth being the main severity indicator. They interpret the pattern forensically: paired bruises on opposing bones reveal the mechanism (the classic lateral femoral and tibial bruises of a pivot-shift knee injury, for instance). They check the overlying cartilage for damage, since the same impact often injures both, and scan for the ligament or tendon injuries that usually accompany significant bruises. The bruise is reported as both a finding and a clue.

Where it commonly shows up

• knee
• femur
• tibia
• hip
• ankle

Questions to ask your doctor

• How extensive is the bone bruise?
• What injury mechanism does the pattern suggest?
• Is the overlying cartilage damaged?
• Are there associated ligament or tendon injuries?
• How long will it take to heal?

Common questions

What does a bone bruise feel like?

Often a deep, persistent ache at the injury site that outlasts the initial swelling — pain with weight-bearing or pressure that can linger for weeks. Because the X-ray is normal, people are sometimes surprised by how long it hurts. The pain typically fades gradually as the marrow heals over weeks to months.

Why didn't it show on my X-ray?

Because a bone bruise injures the marrow inside the bone while leaving the hard outer shell intact — and X-rays show the shell's shape and density, not the marrow's condition. This is normal and expected, not a missed finding. MRI is the test that sees marrow, which is why it is ordered when pain persists after a normal X-ray.

Can a bone bruise turn into a fracture?

A bone bruise itself is not a crack and does not typically “become” a fracture — but it signals that the bone absorbed significant force, and the area is temporarily weakened while it heals. That is why doctors advise protecting it during recovery. Your doctor will tell you what activity is safe while the bruise resolves.

Related conditions

• Edema — What It Means on Your Report
• Fracture — What It Means on Your Report
• Stress Fracture — What It Means on Your Report