Femoral Neck Stress Fracture

The VerdictMODERATE CONVICTION

Deep groin pain in a runner can be a cracked hip bone an X-ray misses — stop and scan.

If you're a runner or recruit with deep groin pain that gets worse the more you run, stop running today and ask for an MRI — not just an X-ray. A normal X-ray does not rule this out.

The bone in the neck of your thigh is cracking from repeated impact faster than it can heal.
A normal X-ray does NOT rule this out — early on it looks fine, so people keep running on a fracture.
Watch for deep groin pain that worsens with running, pain at night, or not being able to put weight on the leg — get an MRI and see a specialist.

The neck of your thigh bone is like a paperclip you keep bending. Bend it occasionally and it's fine; bend it the same way over and over with no rest and a hairline crack forms. The pain is the bone warning you it can't repair as fast as you're loading it. One edge of that "paperclip" is being pulled apart rather than squeezed together — that's the side that can snap.

What Works

For a high-risk fracture, the highest-value "treatment" is recognising it and getting it to the right specialist. This is not a load-it-and-rehab condition.

1. Stop impact loading + urgent MRI HIGH

On clinical suspicion, stop all running, jumping, and marching immediately and arrange an MRI. Do not clear the patient on a normal radiograph — early X-rays are frequently occult. This single step is the highest-value intervention.

2. Risk-stratify and refer high-risk fractures HIGH

MRI shows the side (compression vs tension) and grade. Tension-side, ≥50% of neck width, complete, or displaced fractures lean strongly toward surgical fixation (cannulated screws) to prevent displacement. These go to a surgeon, not the gym.

3. Bone-health & energy-availability workup MODERATE-HIGH

Screen every case: bone density (DXA), vitamin D, energy availability, menstrual status where relevant, and disordered-eating history. Restrictive eating plus prior low-energy fractures is associated with repeated bone stress injuries. Fixing the cause is how you prevent recurrence.

Exercise prescription note: There is no validated early loading program for an unhealed femoral neck stress fracture, because loading is the danger. Structured reloading begins only after orthopaedic clearance — graded weight-bearing, then low-impact, then running, each stage pain-free and 24 hours symptom-free before progressing.

See Tier 2 / Tier 3 management

4. Protected weight-bearing then graded reloading MODERATE

For stable compression-side fractures under ~50% of neck width, a period of protected or non-weight-bearing followed by gradual return is reasonable, under close orthopaedic supervision with serial review.

5. Image the contralateral hip MODERATE

These fractures are often bilateral, and the other hip can be fractured while painless. Screen both when one side is positive.

6. Maintain fitness with cleared non-impact modalities EMERGING

Pool work or a stationary bike to keep fitness up, but only once pain-free and cleared. If anything reproduces the groin pain, stop.

What Doesn't Work

Continuing to run / loading through it — this is how a stress fracture becomes a displaced fracture with avascular necrosis.
Treating it as a hip-flexor or adductor "groin strain" — soft-tissue rehab on a bony stress fracture wastes time and risks progression.
Clearing the patient on a normal X-ray — early films are frequently occult; the fracture is still there.
A home strengthening program for an unhealed high-risk fracture — there is no validated early loading protocol.

Return to Training

Return is gated on healing and pain-free loading, not on a calendar date. Reported healing times are wide and individual.

Orthopaedic confirmation of clinical and radiographic healing
Pain-free full weight-bearing and pain-free walking
Pain-free at the extremes of hip range, including internal rotation
Pain-free graded loading (weight-bearing → low-impact → impact) with no pain during or 24 hours after
Underlying cause addressed (training load corrected; bone health and energy availability optimised)
No night or rest pain

⚠ Red Flags — Refer First

Any suspected femoral neck stress fracture is a refer-first condition. These features make it urgent.

Tension-sided, displaced, or complete fracture on imaging — high risk of progressing to a broken hip.
Hip joint effusion on MRI — predicts a high-grade injury, even before a fracture line is visible.
Can't put weight on the leg, or a sudden spike in pain — possible displacement.
Night pain or rest pain — suggests a higher-grade injury or a non-stress cause that needs screening.
Low energy availability / RED-s / Female Athlete Triad features — restrictive eating, missed periods, prior stress fractures.

Refer to orthopaedics urgently for any confirmed or suspected high-risk fracture. Go to A&E if you cannot weight-bear or displacement is suspected. A normal X-ray does NOT clear this.

If you're a runner or recruit with deep groin pain that gets worse the more you run, stop running today and ask for an MRI — not just an X-ray.

Early X-rays often look normal, so the fracture gets missed and loaded. An MRI catches it, and catching it early is what protects the hip.

Do it now. Stop the impact and book the scan.

Conviction MODERATE

The recognise-and-refer spine is strongly supported. Specific rehabilitation dosing and surgical-technique choice are not.

Endpoint-stratified: recognition, MRI-as-standard, the compression-vs-tension distinction, and early-diagnosis-prevents-displacement are all HIGH. Bone-health workup and effusion-predicts-high-grade are MODERATE-HIGH. Conservative thresholds and contralateral screening are MODERATE. Specific rehab dosing and surgical technique are LOW. A validated special test and a return-to-sport battery are DATA UNAVAILABLE.

What would change my mind — diagnosis

A validated bedside test with published sensitivity/specificity for femoral neck stress fracture would change the "diagnosis is suspicion + MRI" stance. None currently exists.

What would change my mind — return to sport

A prospective multi-centre cohort of MRI-confirmed fractures, stratified by side, grade, and energy availability, with a pre-registered objective return-to-running clearance battery and ≥2-year follow-up, would convert the LOW conviction on rehab dosing and return criteria to MODERATE-HIGH.

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The Full Picture — Anatomy, Diagnosis & Evidence

What's Actually Going On

The femoral neck is the narrow bridge of bone between the ball of the hip and the shaft of the thigh bone. With repeated impact, microdamage builds up faster than the bone repairs it, producing first a stress reaction (bone swelling) and then a true fracture line.

The neck carries an uneven load: the inner-lower edge is under compression, the outer-upper edge is under tension. Compression-side fractures are lower-risk and often heal with offloading. Tension-side fractures are high-risk — that edge combines high pulling force with a poor blood supply, so it tends to progress, heal slowly, or fail to heal. Missed or loaded, it can break completely, risking death of the femoral head (avascular necrosis) and nonunion.

How to Identify It

Insidious, deep groin or hip pain that builds over weeks, worsens with impact, and eases with rest. Pain at the extremes of hip motion, especially internal rotation. There is often a recent training spike. Reproduction of groin pain on a single-leg hop is a clinical flag.

The honest part: no orthopaedic special test has published accuracy for this fracture. Diagnosis is clinical suspicion plus MRI.

Single-leg hop (pain provocation) Sn/Sp: DATA UNAVAILABLE
Pain at end-range hip internal rotation Sn/Sp: DATA UNAVAILABLE
MRI — the actual diagnostic standard; grades the injury, shows the side, shows effusion

The Debate

How aggressively to operate

Threshold reviews (PMID 35234724, 2022; 33433591, 2022)

Stable compression-side fractures under 50% of neck width can be managed without surgery, with offloading and close review.

Case + review (PMID 33782932, 2022)

Fix even complete undisplaced fractures surgically to prevent displacement and speed return.

Side and grade drive the call, and it is surgeon-dependent. Tension-side, ≥50% width, complete, or displaced = surgical. Stable compression-side <50% may be conservative under supervision. No physiotherapy CPG exists for this condition as of 2026.

Honest Limitations

No RCTs, no rehab-protocol trials

The whole evidence base is reviews, registries, and case series. The condition is too rare and high-consequence to randomise. Any "protocol" is consensus and pathway-based, not trial-validated.

Two populations get conflated

Young-athlete fatigue fractures and older insufficiency fractures (one registry's mean age was 58, 75% women) are mixed in summary numbers. Mechanism and management differ.

Return-to-sport is an evidence void

There is an explicit lack of high-quality return-to-activity data, and reported healing times range from about 8 to 121 weeks. Return is individualised, not calendar-based.

The Nuance

Surgical fixation vs conservative, cinematic

Surgery vs conservative: a stable compression-side fracture can heal with offloading; a tension-side fracture is treated aggressively because the downside (avascular necrosis, nonunion) is severe. In one small fixation review (13 subjects), radiographic healing averaged about 33 weeks with a very wide range and no significant difference between fixation constructs — too small to rank techniques. Beware: the biomechanical "which screw is best" studies are about acute traumatic fractures, not stress fractures.

Sources

PMID 26972260 (2016) — High-Risk Stress Fractures: the tension-side femoral neck combines high tensile load with low blood flow, hence progression/nonunion risk.
PMID 35234724 (2022) — Athletes and military review: <50% width nonsurgical, ≥50%/complete surgical; hip effusion is a risk marker; return-to-activity data sparse.
PMID 35077440 (2022) — Updated review: radiographs often occult, MRI superior, treatment by MRI morphology + effusion, untreated progresses to displaced fracture.
PMID 28473086 (2017) — ACR Appropriateness Criteria (GRADE-assessed): imaging modality selection; prompt action important at the femoral neck.
PMID 36611263 (2023) — Hip joint effusion on MRI predictive of a Grade 4 femoral neck stress injury.
PMID 26085653 (2016) — Bilateral fractures in recruits with unilateral symptoms; screen the contralateral hip; vitamin D deficiency signal.
PMID 35523419 (2022) — Restrictive eating + prior low-energy fractures associated with multiple bone stress injuries (N=51 female runners).
PMID 35417029 (2022) — Swedish Fracture Register (N=146): epidemiology, 40% bone-remodeling disorders, age-stratified treatment.
PMID 33722406 (2021) — Operative fixation review (N=13): healing avg ~33 weeks, no significant difference between constructs.
PMID 12145125 (2002) — Importance of clinical suspicion and early review to prevent progression to displacement.
Burge AJR 2018; Taddeo Acta Biomedica 2019; Miyake Semin Musculoskelet Radiol 2024 — preflight-sourced landmark / classification / management references.