The Role of Arthrogenic Muscular Inhibition in Patellofemoral Pain and the Response to an Exercise Programme

Plain-language summary

Patellofemoral pain (PFP) is the most diagnosed condition in individuals with knee complaints. Studies revealed that one third of individuals with PFP suffer from persistent complaints, indicating that current treatments fail to prevent the chronicity of symptoms. Considering that current treatment-strategies of patients with PFP seem to be unable to avoid the development of chronic symptoms, the question arises if the underlying factors of PFP are understood sufficiently. Current research focuses predominantly on muscle strength assessment by means of a maximum voluntary contraction (MVC), even though, weakness might not only be caused by a reduced voluntary contraction but also by an involuntary ability to contract the muscle fully, which is named arthrogenous muscular inhibition (AMI). Although AMI has been proven to be present in a wide range of knee joint pathologies to date it remains unclear whether patients with PFP are weak or inhibited. It remains also unclear if there exists a causal link between AMI and biomechanical alterations. Previous studies investigated the influence of exercise treatment on muscular strength, function and pain. However, to date no study investigated the influence of the currently recommended exercise treatment on AMI. Thus, the analysis of the effect of a 6 week exercise treatment might yield further insights if a specific exercise treatment can reduce AMI, improve functional performance and reduce pain. Methods: The investigators will invite 40 participants with PFP and 40 healthy controls to take part in the study. As a basis investigation kinematic, kinetic measures, and surface electromyographic (sEMG) of 4 lower limb muscles will be taken during functional tasks. Muscle strength and AMI of the quadriceps, muscle flexibility, and a posture assessment of the patella as well as the foot will be carried out. All participants with PFP will then receive a 6 week exercise programme to follow. After six weeks, the participants with PFP will attend the Salford university, where they will be reassessed. Expected outcomes: The study will investigate if AMI is present in participants with PFP and if AMI is directly linked to functional performance. In addition this study will investigate if a specific exercise treatment can reduce AMI and improve functional performance.

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