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.
Study Type
OBSERVATIONAL
Enrollment
126
Runners with lower or different exposure to these factors: other predominant terrain types (e.g., asphalt or trail), lower accumulated elevation gain, and/or lower levels of internal load and training volume.
Universidad de Oviedo
Oviedo, Principality of Asturias, Spain
Measurement of patellofemoral pain over the previous three months.
This variable will be defined according to the International Consensus on Patellofemoral Pain. Participants will be classified as positive cases if they report anterior or retropatellar knee pain in the previous three months, exacerbated by at least one weight-bearing, knee-flexion activity (e.g., running, stair ambulation, slopes, or squatting), with a duration of ≥4 weeks or ≥2 episodes during that period
Time frame: Screening visit
Measurement of functional severity of patellofemoral pain
Functional severity will be assessed using the Spanish-validated version of the Kujala Anterior Knee Pain Scale. This is a condition-specific 13-item questionnaire that evaluates functional limitations, symptoms, and the ability to perform knee-loading activities. Total scores range from 0 to 100, with higher scores indicating better function and, therefore, lower severity.
Time frame: Screening visit
Measurement of terrain exposure (previous 3 months)
This variable will capture the type of terrain on which the runner habitually trains (asphalt, trail, and mountain). Participants will report the approximate percentage of total kilometers completed on asphalt, trail, and mountain terrain over the previous three months.
Time frame: Screening visit
Measurement of weekly positive and negative elevation gain
This variable will be recorded as an average value (meters per week, or normalized as meters per 10 km), given that eccentric loading and patellofemoral joint stress increase substantially during prolonged downhill running.
Time frame: Screening visit
Measurement of the percentage of downhill kilometers
If mountain terrain is predominant, an additional item will be included to capture the percentage of kilometers run on downhills with a gradient ≥6%.
Time frame: Screening visit
Measurement of training intensity and internal load (previous 4 weeks)
Training intensity will be assessed using Foster's session Rating of Perceived Exertion (sRPE), based on the Borg CR-10 scale (0-10). Participants will report their mean perceived exertion for each session type (e.g., easy runs, intervals, hill sessions) over the previous four weeks. Weekly internal load will be calculated by multiplying the sRPE value by session duration (minutes).
Time frame: Screening visit
Measurement of training volume over the previous 4 weeks
This variable will include weekly running distance (kilometers), training frequency (number of sessions per week), and session duration (minutes per session).
Time frame: Screening visit
Measurement of mean running pace over the previous 4 weeks
This variable will be recorded as minutes per kilometer (min/km).
Time frame: Screening visit
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