Stress Fractures

Patients describe localised activity-related bone pain - the cardinal feature. Pain at a specific site is provoked by impact activity and initially relieved by rest, with insidious onset over days to weeks during increased loading rather than an acute traumatic event. Progression follows a predictable pattern: pain initially during or after high-impact activity, then earlier at lower loads, eventually with walking or at rest. Activity-specific (running, marching, jumping, dancing), reproducibly provoked by the same activity. Always ask about training history, RED-S screening (menstrual history in females, energy availability, dietary restriction; in males - low libido, low energy, recurrent illness), medications (corticosteroids, PPIs), family history of osteoporosis, and smoking.

Examination: focal well-localised bony point tenderness is the most important clinical finding - patients can often identify the exact spot with one finger. The hop test (single-leg hopping reproducing sharp focal pain at the fracture site) supports the diagnosis but must NOT be performed if femoral neck stress fracture is suspected because of displacement risk. The fulcrum test (patient seated, examiner places a fist under the mid-thigh as a fulcrum and applies downward force) is useful for suspected femoral shaft or neck involvement. Site-specific findings: tibial (focal posteromedial or anterior tenderness), metatarsal (focal dorsal tenderness, mild swelling), navicular (tenderness over the central dorsal navicular at the N spot), femoral neck (groin pain, pain at extremes of hip range of motion - do NOT hop test), medial malleolus (focal tenderness at the malleolus tip). Biomechanical assessment covers foot posture, ankle dorsiflexion, calf endurance, and hip abductor strength.

Differentials: MTSS (diffuse rather than focal tenderness), CECS, tendinopathy (tenderness along the tendon not the bone), bone tumour (osteoid osteoma with night pain relieved by NSAIDs; osteosarcoma), osteomyelitis, and referred lumbar pain.

Plain radiographs are first-line and readily available but are often normal early and should not be used to exclude stress fracture - changes take 2-6 weeks to appear. They are most useful for the dreaded black line at the anterior tibia and for excluding alternative bony pathology.

MRI is the investigation of choice - the most sensitive and specific test, detecting bone stress injury within days. It demonstrates bone marrow oedema, periosteal oedema, and the fracture line. The Fredericson grading: Grade 1 = periosteal oedema only (T2); Grade 2 = periosteal plus mild marrow oedema (T2); Grade 3 = periosteal plus extensive marrow oedema (T1 and T2); Grade 4 = visible fracture line with marrow oedema. Site and risk status are more important for management than MRI grade alone.

CT is not first-line for most fractures but is especially useful for navicular characterisation and pars interarticularis defects. Bone scan is sensitive but non-specific and has been largely superseded by MRI. POCUS may show periosteal thickening in early stress fractures as an adjunct.

Bloods are not routine for an isolated first stress fracture. Consider vitamin D, bone profile, FBC, ferritin, thyroid function, and reproductive hormones for recurrent, high-risk, or RED-S-suspected cases. Many SEM physicians target vitamin D over 75 nmol/L in athletes with bone stress injuries. DEXA scan should be considered for recurrent stress fractures, prolonged amenorrhoea (over 6 months), or suspected RED-S.

Management depends fundamentally on whether the fracture is at a low-risk or high-risk site.

General principles: explain the bone stress continuum and distinguish low-risk from high-risk, correct training errors, and optimise bone health while actively assessing for and addressing RED-S (IOC REDs CAT2).

Low-risk stress fractures (posteromedial tibia, 2nd-4th metatarsal shaft, fibula, calcaneus, pubic rami): relative rest with activity modification, weight-bearing as tolerated, maintenance of non-impact fitness, pain as a guide, and progressive return to impact once pain-free (typically 4-12 weeks). Paracetamol is preferred for pain relief; many clinicians avoid prolonged NSAIDs during active bone healing.

High-risk stress fractures require specialist input:

• •Anterior tibial cortex (dreaded black line): tension-side with high non-union risk, typically requires prolonged offloading of 3-6 months or longer, with surgery for non-union.
• •Navicular (avascular central third): non-weight-bearing for 6-8 weeks for non-displaced fractures, with CT for characterisation. Surgery for displaced or non-union. Return to sport at 3-6 months.
• •Femoral neck: the most dangerous stress fracture in sport. Compression-side non-displaced fractures need strict protected weight-bearing with close monitoring; tension-side or displaced fractures are surgical emergencies. Do NOT hop test.
• •Proximal fifth metatarsal (Jones region): tenuous blood supply. Non-operative management is strict non-weight-bearing for 6-8 weeks; many athletes undergo early surgical fixation (intramedullary screw) for faster return at 6-12 weeks.
• •Medial malleolus: vertical fracture with poor healing, often needs screw fixation.

Bone health optimisation: vitamin D (supplement if deficient, target over 75 nmol/L in athletes), calcium (at least 1000 mg/day), and energy availability (address RED-S). For severe recurrent insufficiency fractures, bone-modifying agents may occasionally be considered under specialist guidance.

Refer for all high-risk sites, recurrent stress fractures (RED-S assessment), suspected femoral neck stress fracture, or failure to improve with appropriate management.

Phase 1 (offloading, 0-6 weeks): reduce or eliminate impact loading. Low-risk fractures are weight-bearing as tolerated; high-risk follow site-specific protocols. Maintain fitness with cycling, swimming, aqua jogging. Begin non-impact strengthening: calf (particularly soleus), hip abductors, quadriceps, hamstrings. Address bone health and RED-S.

Phase 2 (progressive loading, 6-12 weeks for low-risk, longer for high-risk): graduated return to weight-bearing impact with walking programmes then walk-run intervals. Pain at the fracture site during activity means the load is too high. Continue strengthening.

Phase 3 (return to sport, variable by site): progressive running, distance before speed, with gradual reintroduction of speed work, hills, and sport-specific drills.

Approximate timelines (guides only): fibula 4-6 weeks, metatarsal shaft (2nd-4th) 6-8 weeks, posteromedial tibia 8-12 weeks, navicular 3-6 months, anterior tibia 3-6+ months, femoral neck (non-displaced compression side) 3-4 months, proximal 5th metatarsal 6-12 weeks (operative).

Return-to-sport criteria: pain-free at fracture site during and after sport-specific activity, adequate strength (calf endurance 25 or more single-leg raises), good biomechanical control, and bone health/RED-S addressed.

Prevention: training-load management, ongoing strengthening, appropriate footwear, running-surface variation, bone health optimisation, RED-S management. Previous stress fracture is the strongest predictor of recurrence.

• •Fredericson et al. (1995, AJSM) - MRI grading of bone stress injury (Grade 1 periosteal oedema to Grade 4 discrete fracture line) remains the standard staging in UK SEM practice.
• •IOC REDs CAT2 (Mountjoy et al., 2023, BJSM) - Current consensus framework for screening and managing Relative Energy Deficiency in Sport; recurrent bone stress injury is a key trigger.
• •Warden et al. (2014, BJSM) - High-risk sites (anterior tibial cortex, femoral neck tension side, navicular, proximal 5th metatarsal, medial malleolus) need early specialist review.
• •BOAST / BASEM consensus on femoral neck stress fracture in sport - Groin pain with antalgic gait in a runner mandates urgent imaging; displaced femoral neck stress fracture is a surgical emergency.
• •BNF / SEM consensus - Paracetamol is preferred during active bone healing; prolonged NSAIDs may impair bone remodelling and are best avoided.

• •Identifying HIGH-RISK sites is the most important clinical skill: anterior tibial cortex (dreaded black line, tension side), navicular (avascular watershed), femoral neck (tension side), proximal 5th metatarsal (Jones region), medial malleolus. All need specialist referral.
• •Focal point tenderness = stress fracture; diffuse tenderness over 5 cm = MTSS. A normal X-ray does NOT exclude a stress fracture - MRI is the investigation of choice.
• •Groin pain in a runner = femoral neck stress fracture until proven otherwise. Do NOT hop test. Urgent MRI if X-ray is normal; displaced fractures are surgical emergencies.
• •Anterior tibial cortex = tension side = dreaded black line = high non-union risk. Posteromedial tibia = compression side = lower risk.
• •Navicular stress fracture is commonly missed - vague dorsal midfoot pain at the N spot. CT characterises the fracture, and the Jones zone of the fifth metatarsal often needs early operative fixation.
• •Fatigue fracture = abnormal load on normal bone (athletes); insufficiency fracture = normal load on abnormal bone (RED-S, osteoporosis). Always screen for RED-S using IOC REDs CAT2; consider DEXA in recurrent stress fractures.