🏃 Tibial Stress Fracture Bone Scan Simulator

Normal Bone Remodeling

Healthy bone constantly rebuilds itself in balance.

• ~120 days: Remodeling cycle (resorption through repair)
• 1:1: Osteoclast:osteoblast ratio (coupled activity)
• ~10%: Annual bone turnover (of adult skeleton)
• ~5 mm: Tibial cortex thickness (mid-shaft average)

Coupled resorption and formation

Osteoclasts dig, osteoblasts refill, in sequence.

Mechanical loading signal

Everyday load nudges bone to strengthen slightly.

Baseline imaging appearance

A healthy bone scan shows only faint, even uptake.

Reactive Bone Edema

Training outpaces repair, and fluid starts pooling.

• 2–3 wk: Time to onset (of ramped-up training)
• I–II: Bone scan grade (mild focal uptake)
• 1: MRI edema grade (mild marrow signal)
• Post-activity: Symptom pattern (ache after loading)

Remodeling falls behind

Resorption briefly outruns new bone formation.

Fluid accumulation begins

Interstitial fluid seeps into stressed marrow space.

Scintigraphy sensitivity

Bone scan detects change before symptoms flare.

Periosteal Reaction

The bone surface itself becomes inflamed and reactive.

• STIR/T2: MRI sequence (best periosteal contrast)
• Periosteum: Edema location (along posteromedial tibia)
• II: Bone scan grade (moderate linear uptake)
• Focal tenderness: Palpation finding (along shaft)

Periosteal signal appears

A bright rim traces the outer bone surface.

Load site correlation

Reaction clusters where bending stress peaks.

Still reversible

Rest at this stage usually restores normal bone.

Stress Reaction

Marrow edema deepens as microdamage quietly accumulates.

• 3: MRI edema grade (moderate-severe marrow signal)
• III: Bone scan grade (intense focal uptake)
• ~78%: Cortical integrity (microcrack accumulation)
• Elevated: Return-to-run risk (without load reduction)

Microdamage outpaces repair

Microcracks accumulate faster than osteoblasts fill them.

Marrow signal intensifies

MRI edema now spans a wider marrow region.

Last stage before fracture

Continued load pushes bone toward a true break.

Stress Fracture Line

A visible cortical line marks true bone failure.

• IV: Bone scan grade (fusiform intense uptake)
• Fracture line: MRI finding (low-signal cortical break)
• ~55%: Cortical integrity (and falling under load)
• 6–12 wk: Typical healing time (with load modification)

Cortical line becomes visible

A dark fracture line crosses the cortex on MRI.

High-risk anterior tibial cortex

Anterior cortex fractures heal slowly, need caution.

Healing reverses the picture

Rest lets uptake and edema gradually recede.