Bone stress injuries (BSIs) are a spectrum of overuse injuries to bone caused by repetitive loading that exceeds the bone's capacity to remodel and repair. They range from stress reactions (periosteal and bone marrow oedema without a discrete fracture line) to stress fractures (a visible fracture line within oedematous bone) and, if unmanaged, to complete fracture. BSIs are among the most common overuse injuries in sport and military populations. The tibia is the most commonly affected bone overall, followed by metatarsals, fibula, navicular, femoral neck, and pelvis. The most critical clinical concept is the LOW-RISK vs HIGH-RISK site framework - high-risk sites (femoral neck tension side, navicular, anterior tibial cortex, proximal 5th metatarsal, patella, medial malleolus, talus, sesamoids) have a propensity for non-union, delayed healing, or catastrophic fracture and often require more aggressive management. A normal X-ray does NOT exclude a BSI - MRI is the preferred advanced imaging modality. RED-S (Relative Energy Deficiency in Sport - the broader successor to the female athlete triad) is a major systemic risk factor and should be screened for in every athlete with a BSI. UK practice combines fracture management principles, the IOC REDs CAT2 framework, and sports medicine consensus.
Normal bone remodelling: bone is a dynamic tissue that continuously remodels in response to mechanical loading - Wolff's law states that bone adapts its structure to the loads placed upon it. Normal remodelling is a balanced cycle of osteoclastic resorption then osteoblastic formation; bone is transiently more porous after resorption and before formation completes, producing a temporary window of relative weakness. Adaptation lags rapid increases in load.
Pathogenesis: when repetitive loading exceeds the bone's capacity to remodel and repair, microdamage accumulates:
Fatigue fractures (abnormal/excessive load on normal bone - the typical athletic and military pattern) versus insufficiency fractures (normal physiological load on abnormal/weakened bone - osteoporosis, metabolic bone disease, corticosteroid use).
The LOW-RISK vs HIGH-RISK framework:
Low-risk sites (generally heal well with activity modification):
High-risk sites (propensity for non-union, delayed healing, or catastrophic fracture):
Other important BSIs: pars interarticularis stress fracture (spondylolysis) of the lumbar spine in adolescent athletes in extension/rotation sports (cricket fast bowlers, gymnasts, rowers); presents with extension-related low back pain. MTSS ('shin splints') causes diffuse tenderness over more than 5 cm of the posteromedial tibial border, distinct from the focal point tenderness of a BSI.
Bone health and RED-S: Relative Energy Deficiency in Sport (the broader successor to the female athlete triad - low energy availability, menstrual dysfunction, low BMD) is a major systemic risk factor that affects both males and females. Low energy availability produces hormonal disruption (menstrual dysfunction in females, low testosterone in males), impaired bone formation, low BMD, and increased fracture risk. Screen for RED-S in every athlete with a BSI. Recurrent BSIs mandate multidisciplinary assessment via the IOC REDs CAT2 framework.
Risk factors: rapid training load increase (the most important modifiable factor), previous BSI (the strongest predictor of recurrence), RED-S, female sex, menstrual dysfunction, menopause, low BMI, low BMD, vitamin D deficiency, inadequate calcium intake, pes cavus, leg length discrepancy, muscle weakness or fatigue, inappropriate or worn footwear, hard surfaces, military basic training, running, and dance.
Sign up to get full access to 10 topics of your choice, including all sections, clinical pearls, and exam tips.
Sign up free10 free topics included with your account. Full access from £24.17/month.
Sections included with full access