Relation between knee extensor torque with performance in the Single Leg Hop test of women with and without patellofemoral pain

Abstract

Patellofemoral Pain (PFP) is a multifactorial disorder defined as a diffuse anterior knee pain of insidious onset. The symptoms are exacerbated by activities such as stair ascent and descent, squat, sitting for long time, jumping and landing. The relationship between altered muscle function of quadriceps femoris with PFP has been widely studied. Reduced torque, total volume, electromyography activity and knee extensor muscle strength are reported in individuals with PFP. Previous studies have reported that lower knee extensor torque is a risk factor for PFP development and the increase in knee extensor strength results in better clinical outcomes in individuals with PFP. However, the evaluation of quadriceps torque usually depends on expensive equipments such as isokinetic and manual dynamometers. The expensive cost of these equipment limits their use in the clinical environment. On the other hand, clinical tests are low-cost and easily administered. The performance in Single Leg Hop Test (SLHT) is related with quadriceps femoris control and strength. The lower performance in this test was associated with lower femoral quadriceps extensor torque and power in other population. However, no studies has investigated the association between SLHT and knee extensor torque in individuals with PFP. Investigating if the lower performance in SLHT could indicate a reduction in knee extensor torque and power evaluated in the isokinetic dynamometer may bring important information to clinical practice and assist in low-cost identification of quadriceps femoris function in individuals with PFP. Therefore, the aim of this project is to investigate if women with and without PFP have changes in the peak, power and rate of force development of knee extensor concentric torque and in the performance of SLHT and how these variables are associated. Women with and without PFP aged between 18 to 35 years will be recruited. The participants will undergo an experimental protocol consisting of: 1) An initial evaluation of anthropometric characteristics, knee pain level in the last month and at the moment with a VAS, Baecke questionnaire and AKPS score; 2) Execution of the SLHT; 3) Measurement of the knee extensor concentric torque through the isokinetic dynamometer. The variables of knee extensor torque (peak, power, and rate of force development) will be calculated in the software MATLAB® and the mean in three jumps of SLHT will be considered for statistical purposes. Statistical analyzes will be done to investigate differences between groups (independent t test or Mann-Whitney test) and to evaluate the relation between knee extensor torque and the performance in SLHT (Pearson correlation coefficient or Spearman correlation coefficient).