Bone stress injury recovery and return to sport in runners: a multi-site prospective observational cohort study protocol across the USA and Canada.

There is no consensus on how to define or assess bone stress injury healing, limiting comparability across studies and development of evidence-based return-to-sport guidelines.

• Clinical, functional, and imaging outcomes for BSI healing are used inconsistently across studies
• The lack of standardization has prevented the development of evidence-based return-to-sport guidelines
• BSIs are associated with prolonged recovery and high rates of reinjury

The study will enrol male and female runners with MRI-confirmed bone stress injuries of the tibia, metatarsals, femoral neck, or sacrum across four clinical and academic research sites in the USA and Canada.

• Participants must be enrolled within 3 weeks of diagnostic MRI
• The study spans four clinical and academic research sites in the USA and Canada
• The study targets four anatomical sites: tibia, metatarsals, femoral neck, and sacrum
• Both male and female runners are included
• Minors may participate with parental consent and participant assent

The study will follow participants longitudinally for 1 year through recovery, return to sport, and full sport participation.

• This is a 1-year prospective cohort study design
• Follow-up spans the full arc from recovery through return to sport and unrestricted participation
• The longitudinal design allows characterization of the time course and variability of healing outcomes

Candidate outcomes for bone stress injury healing include time to pain-free functional milestones, completion of a return-to-run protocol, medical clearance for unrestricted activity, and changes in MRI grade and clinical severity scores.

• Pain-free functional milestones include activities such as hopping and jogging
• Outcomes span function, imaging, and clinical domains
• MRI grade changes are included as an imaging outcome
• Medical clearance for unrestricted activity serves as a clinical endpoint

Secondary and exploratory measures include training patterns, wearable-derived activity and sleep metrics, biomechanical assessments, and serum proteomic profiles.

• Wearable devices will capture activity and sleep metrics
• Serum proteomic profiles are included as exploratory biological measures
• Biomechanical assessments are included as secondary measures
• Training patterns will be tracked throughout the follow-up period

The study will explore associations between healing outcomes and subsequent bone stress injuries within 1 year using regression models.

• Regression models will be used to explore associations between candidate outcomes and reinjury
• The reinjury outcome window is 1 year
• Descriptive statistics will characterize the time course and variability of candidate outcomes
• High rates of reinjury are noted as a key clinical concern motivating the study