Influence of Training Surface and Mechanical Load on the Prevalence of Patellofemoral Pain in Recreational Runners

Influence of Training Surface and Mechanical Load on the Prevalence of Patellofemoral Pain in Recreational Runners: A Cross-Sectional Cohort Study

Background. Patellofemoral pain (PFP) is one of the most common causes of knee pain in recreational runners and is exacerbated by activities that load the patellofemoral joint. Although biomechanical differences between running surfaces and elevation profiles have been documented, the influence of terrain type and training load on PFP in non-professional runners remains poorly defined.

Objective. To examine the association between predominant training terrain and the presence of PFP in non-professional runners, and to describe its functional severity. Secondarily, to analyze the relationship between terrain exposure, elevation, training load and volume with PFP, as well as the potential influence of previous knee history and footwear rotation.

Methods. An observational, analytical, cross-sectional study conducted through an online survey targeting recreational runners. The primary outcome will be the presence of patellofemoral pain, defined according to the 2016 International Consensus, and functional severity will be assessed using the Spanish-validated Kujala Anterior Knee Pain Scale. Exposures will include the percentage of kilometers run on each terrain type, positive and negative elevation gain, internal load (session rating of perceived exertion × duration), training volume, and running pace. Potential confounders will include age, sex, body mass index, running experience, training frequency, previous knee history, lower-limb strength, accumulated elevation gain, and footwear rotation. Descriptive analyses and logistic regression models will be performed to identify independent associations.

Expected results. To estimate the prevalence of PFP in recreational runners, identify terrain- and load-related factors associated with its occurrence, and define a predictive model to inform prevention strategies and training planning.

Inclusion Criteria:

• Participants aged 18 years or older.
• Recreational (non-professional) runners.
• Have run regularly over the previous 3 months (at least once per week).
• Are able to report their predominant training terrain (asphalt, trail, or mountain).
• Have or do not have patellofemoral pain.
• Have provided written informed consent.

Exclusion Criteria:

• Have had a complete cessation of running for ≥4 weeks within the previous 3 months.
• Have undergone major knee or ankle surgery within the past year.
• Have a diagnosis of conditions that clearly alter gait or running pattern.
• Present severe knee disorders that preclude accurate assessment of patellofemoral pain.
• Have incomplete questionnaires for essential variables (terrain type, patellofemoral pain, AKPS, training load, or training volume)