The Role of Vertical Stiffness in Predicting the Incidence of Patellofemoral Pain Syndrome: A Prospective Cohort Study

Document Type : Original Articles

Authors
Effat Hoseinzadeh 1
Mansour Eslami 2
Mohammad Taghipour 3
Afshin Fayyaz-Movaghar 4
1 Assistant Professor, Department of Sport Sciences, School of Behavioral Sciences, University of Birjand, Birjand, Iran
2 Associate Professor, Department of Sports Biomechanics and Motor Behavior, School of Physical Education and Sport Sciences, University of Mazandaran, Babolsar, Iran
3 Professor, Department of Physiotherapy, School of Rehabilitation Sciences, Babol University of Medical Sciences, Babol, Iran
4 Assistant Professor, Department of Statistics, School of Mathematical Sciences, University of Mazandaran, Babolsar, Iran
10.48305/jrrs.2026.46446.1151
Abstract
Introduction: Patellofemoral pain syndrome (PFPS) is one of the most common overuse injuries of the lower extremity, particularly prevalent among active individuals. Despite numerous studies, the biomechanical risk factors associated with its incidence have not yet been fully identified. Vertical stiffness, as a modifiable variable that reflects both kinetic and kinematic components of the movement system, may play an important role in identifying individuals at risk. This study aimed to investigate the role of vertical stiffness in predicting PFPS incidence.
Materials and Methods: In this prospective cohort study, 80 first-year physical education students (50 women and 30 men) who met the inclusion criteria were selected using convenience sampling. Vertical stiffness of both lower limbs was measured during running at the beginning of the academic semester. Participants were followed for 16 weeks, and lower extremity injuries were recorded and confirmed by an orthopedic physician. At the end of the follow-up period, participants were divided into two groups: those with PFPS and those without injury. Differences in vertical stiffness between groups were analyzed using an independent t-test, and the predictive role of vertical stiffness was examined using binary logistic regression.
Results: The mean pre-injury vertical stiffness in the PFPS group was significantly higher than in the uninjured group (P ≤ 0.05). Logistic regression analysis showed that higher vertical stiffness was significantly associated with an increased risk of developing PFPS (OR = 2.078, 95% CI: 1.026-4.207, P ≤ 0.05).
Conclusion: High vertical stiffness is a significant predictor of PFPS incidence. These findings suggest that assessing vertical stiffness may help identify individuals at risk and support the design of prevention strategies targeting biomechanical factors.
Keywords
Patellofemoral pain syndrome
Vertical stiffness
Running
Risk factors
Biomechanics
Subjects
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