Stress Reactions

For Medical Students

What It Shows

A stress reaction is marrow change caused by repetitive loading, with no visible fracture line. 5.13.1 covers bone marrow oedema.

It appears on fluid sensitive sequences, usually in cancellous bone at a loaded site. 5.2.17 covers the STIR imaging.

It matters because it sits on a continuum with a stress fracture, and where a patient sits on that continuum decides how much they are allowed to load. 5.13.3 covers stress fractures.

How It Is Acquired

Use fluid sensitive sequences with fat suppression through the symptomatic region. 5.2.16 covers the fat suppression.

Include a T1 weighted sequence to look for a line the fluid sensitive images hide. 5.2.13 covers the T1 imaging.

Record whether the periosteum, the marrow or both are involved. 5.5.6 covers the bones.

Record the site precisely, because the site decides the risk. 2.2.1 covers the proximal tibia.

Take the training or activity history, since the diagnosis rests on it. 4.2.9 covers the onset.

What Normal Looks Like

Marrow following fat on every sequence at the loaded site. 5.5.6 covers the bones.

No periosteal reaction along the adjacent cortex. 5.3.2 covers the lateral view.

A normal radiograph, which is expected and excludes nothing. 5.3.1 covers the AP view.

Signal matching the other side where both were imaged. 5.20.1 covers structured reporting.

What Abnormal Looks Like

Marrow signal change at a loaded site with no line through it. 5.13.1 covers bone marrow oedema.

Periosteal oedema along the adjacent cortex. 5.3.2 covers the lateral view.

Change concentrated on the compressive side of a bone under varus or valgus load. 3.13.3 covers the varus alignment.

Change at a growth plate in a skeletally immature athlete. 5.15.2 covers the growth plates.

A line appearing on a later scan, which reclassifies the injury. 5.13.3 covers stress fractures.

MRCS Level

How It Is Acquired

In a viva the expected answer treats the finding as a point on a continuum.

The expected points are the fluid sensitive sequences, the search for a line, the periosteum, the site, and the activity history.

Say that imaging grades the severity and the history makes the diagnosis. 5.1.2 covers clinical examination versus imaging.

Say that the grading systems in use are magnetic resonance based and differ from one another. 5.1.7 covers evidence-based imaging.

Say that the decision is about load rather than about the image. 3.4.9 covers the force transmission.

What Abnormal Looks Like

The reasoning expected is that bone remodels to load, and a reaction is remodelling outrun by loading rather than a discrete injury. 3.4.10 covers the shock absorption.

Progression runs from periosteal change, through marrow change, to a line, to a complete fracture, which is why the report should name where it sits. 5.13.3 covers stress fractures.

The site decides whether the continuum is safe to sit on, since some sites heal with reduced load and others progress despite it. 2.1.2 covers the distal femur.

A metabolic or nutritional cause changes the management more than the grade does and is invisible on the scan. 5.1.6 covers imaging pitfalls.

How Good It Is

Magnetic resonance imaging is the best available test for a stress reaction and grades a continuum whose grades are not agreed.

Its best contribution is confirming the site and excluding a line. 5.13.3 covers stress fractures.

It is limited by competing grading systems, by signal that lags the clinical recovery, and by saying nothing about why the bone was overloaded. 5.1.7 covers evidence-based imaging.

No figures appear for accuracy on this page, under decision 028, and no grade boundaries or return to play intervals appear either: those are published quantities from particular cohorts and this environment cannot check them.

FRCS Level

How Good It Is

At decision level the scan sets how much load is permitted and for how long. 3.4.9 covers the force transmission.

A high risk site changes that answer whatever the grade. 2.1.2 covers the distal femur.

Alignment is part of the cause when the change sits on one side of a bone. 3.13.3 covers the varus alignment.

A repeat scan confirms progression or resolution rather than re-grading. 5.13.1 covers bone marrow oedema.

The metabolic and nutritional assessment belongs beside the imaging rather than after it. 5.1.3 covers choosing the correct investigation.

Where It Misleads

The commonest error is reading persistent signal as persistent injury. 5.13.1 covers bone marrow oedema.

A reaction is reported as a fracture because a line was inferred from the oedema. 5.13.3 covers stress fractures.

Incidental marrow change in an athlete is attributed to their symptoms. 5.1.2 covers clinical examination versus imaging.

Change in a skeletally immature knee is read against adult expectations. 5.15.1 covers the normal paediatric anatomy.

Return to load is permitted on the scan rather than on the symptoms. 5.20.8 covers common reporting errors.

Fellowship Level

Where It Misleads

At fellowship level the athlete arrives with serial scans from different departments and a graded report from each. 5.18.1 covers the quantitative MRI.

Grades from different systems are not comparable, so a sequence of grades describes the reporters. 5.20.1 covers structured reporting.

Signal persists long after the bone will tolerate load, so a return to play led by the scan is later than it needs to be. 5.13.3 covers stress fractures.

A reaction recurring at one site after a correct rehabilitation points at alignment, metabolism or technique rather than at the bone. 3.13.3 covers the varus alignment.

Bilateral or multiple sites take the problem out of the knee entirely. 5.13.6 covers transient osteoporosis.

The useful report names the site, the structures involved, whether a line is present, the system behind any grade, and what the scan cannot say about cause. 5.20.1 covers structured reporting.