The influence of knee crepitus on quadriceps avoidance parameters in women with patellofemoral pain

Abstract

Patellofemoral pain (PFP) is a common knee disorder of insidious onset. Knee crepitus is a common clinical sign in individuals with PFP, presenting a prevalence of up to 70% in this population. Although knee crepitus does not seem to be related with poor clinical outcomes in women with PFP, it does seem to generate negative patients' beliefs over the condition. Interestingly, protection mechanisms such as quadriceps avoidance have been also found in individuals with PFP. However, although knee crepitus can negatively affect patient's beliefs, no study has investigated the relationship between knee crepitus with altered movement pattern, specifically quadriceps avoidance in individuals with PFP. The aim of this project is to compare the knee extensor moment, knee flexion angle, amplitude of the electromyography (EMG) activity of Vastus Medialis (VM) and Vastus Lateralis (VL) and co-contraction of quadriceps and hamstrings during a step-down task in women with PFP presenting and not presenting knee crepitus. Women with PFP aged 18 to 35 years will be recruited in Toledo - Ohio. An assessor will perform the knee crepitus test and participants will be asked to perform a step-down task. Kinematic and kinetic data during the step-down task will be obtained by a 3-D motion analysis system through an experimental set up with 9 infrared cameras and one force plate. The variables of interest will be peak knee extensor moment, peak knee flexion, mean amplitude of EMG activity of VM and VL and a co-contraction ratio of quadriceps and hamstrings. Statistical analysis will be performed to investigate between groups differences (independent t test or Mann-Whitney test). (AU)