Intensidade da dor e pico de torque em diferentes amplitudes de extensão do joelho contra resistência em pessoas com dor patelofemoral: um estudo transversal

Abstract

Patellofemoral pain is characterized by insidious-onset peripatellar and/or retropatellar pain, which is exacerbated by activities that increase the load on the patellofemoral joint (PFP), such as squatting, jumping, and stair descent. PFP affects 22.7% of the general population and is more common in women and adolescents. Quadriceps strengthening is widely recommended in the treatment of PFP. However, biomechanical studies have raised concerns regarding the reaction force and stress on the patellofemoral joint during open kinetic chain knee extension, with recommendations for limited range of motion between 90° and 45° of flexion. Therefore, the objective of this study was to compare pain intensity and peak torque during maximal resistance knee extension without weight-bearing across different ranges of motion using an isokinetic dynamometer in individuals with patellofemoral pain. One hundred individuals aged 18 to 35 years with patellofemoral pain, symptoms lasting more than three months, and pain intensity greater than 3 were included. All participants underwent an assessment consisting of 10 maximal repetitions at a speed of 60°/s using an isokinetic dynamometer (Biodex System Pro) across three ranges of motion (45°–0°, 70°–25°, and 90°–45°), in a randomized execution order. Pain intensity was measured using a numeric pain rating scale during two-minute rest intervals between sets. Comparisons of pain intensity across different execution ranges, as well as comparisons of quadriceps peak torque, were conducted using generalized estimating equations (GEE). Age in years, sex (male/female), BMI, symptom duration in months, prior pain (pain intensity [NPRS] in the past month), and kinesiophobia assessed by the Tampa Scale were included as covariates in Model 1. As peak extensor torque was normalized by body weight, BMI was removed as a covariate in Model 2, with the remaining variables from Model 1 retained.Our results showed a significant effect of knee extension range on pain intensity in individuals with patellofemoral pain (P < .01). The 70°–25° range was associated with higher pain intensity compared to 90°–45° (mean difference = 1; 95% CI, 0.4 to 1.6). A significant effect of range of motion on knee extensor torque was also observed (P = .02). The 45°–0° range produced lower torque compared to both 70°–25° (mean difference = -27.5 Nm/kg; 95% CI, -32.5 to -22.5) and 90°–45° (mean difference = -29.9 Nm/kg; 95% CI, -36.4 to -23.3). The effect of range on pain intensity depended on prior pain (P = ,001), whereas the impact of range on peak torque varied by sex (P < .001). Pain intensity and peak knee extensor torque in individuals with patellofemoral pain are influenced by the range of motion during non-weight-bearing exercise. These findings suggest that the choice of execution range should be individualized, taking into account the patient's symptoms and clinical profile. This study adds to the current literature and contributes to the refinement of interventions aimed at quadriceps strengthening, improved knee functional capacity, and overall functionality.