Patellofemoral pain (PFP) is characterized as diffuse anterior knee pain exacerbated by activities that increase compressive forces on the patellofemoral joint. PFP is one of the most frequent musculoskeletal disorders of the lower limbs, affecting one in four physically active individuals. In addition to persisting in about 50% of cases even after treatment, PFP can compromise the function, level of physical activity and quality of life of affected individuals. Its onset can be insidious (insidious-onset PFP) or post-traumatic (post-traumatic PFP). Evidence points to a persistence of symptoms in approximately 70% of individuals after direct trauma to the knee. In addition to long-term persistence, post-traumatic PFP also negatively impacts the function and quality of life of affected individuals. Despite these findings, the vast majority of research on this disorder is performed in individuals with insidious-onset PFP. It is known that insidious onset PFP is associated with several kinetic and kinematic alterations. Since these alterations are modifiable factors, they are commonly the focus of interventions that aim to improve the clinical condition of individuals with insidious-onset PFP. On the other hand, little is known about which alterations are present in individuals with post-traumatic PFP. This can be explained by the fact that the history of trauma, injury and/or knee surgery is considered an exclusion criterion in most studies on PFP. Due to the paucity of cross-sectional studies in individuals with post-traumatic PFP, there is no evidence on which clinical and biomechanical alterations are present in this subgroup when compared to asymptomatic individuals. Furthermore, it is not possible to state that these individuals present the same alterations as individuals with insidious-onset PFP, or whether the currently recommended assessments and interventions can also be used in individuals with post-traumatic PFP. The main objective of this project is to compare clinical and biomechanical variables between individuals with insidious-onset, post-traumatic and asymptomatic PFP. The sample will be composed of men and women between 18 and 35 years old. Data collection will be divided into two stages to be carried out on different days: (1) evaluation of clinical parameters: pain, using the Visual Analogue Pain Scale (VAS); subjective function, assessed by the Anterior Knee Pain Scale (AKPS). Objective function will be evaluated through functional performance in the Single Leg Hop Test, while the flexibility of knee extensors and flexors will be evaluated by the Ely's Test and Straight leg raise test (SLRT), respectively. Biomechanical parameters (hip adduction, knee flexion and abduction angles, knee extensor moment and patellofemoral contact forces) will be collected during the Single Leg Hop for Distance task through a three-dimensional motion analysis system.; (2) evaluation of the maximum torque and rate of torque development of the knee extensors and flexors and hip abductors, using the isokinetic dynamometer. For the statistical analysis, clinical and biomechanical parameters will be compared among groups using a one way analysis of variance or a non-parametric correspondent. When there is interaction and/or main effect (p < 0.05), post-hoc Bonferroni tests will be used for multiple comparisons to identify which groups presented differences, considering a significant p value of 0.05. Mean differences, 95% confidence intervals and pairwise effect sizes (Cohen's d) will also be calculated. The intra-rater reliability will be analyzed by calculating the intraclass correlation coefficient (CCI2,K), two-way random. ICC values will be interpreted as: excellent (e0.90), good (0.75-0.89), moderate (0.50-0.74), or low (<0.50).
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