Influence of step rate and quadriceps load distribution
Patellofemoral pain is an extremely common injury among recreational runners. A stimulation study of running found that the vastus medialis weakness can increase mediolateral patellofemoral joint loads.
Recent imaging studies suggest that bone that patellofemorale pain (PFP) may arise from localized cartilage pressure or subchrondral bone damage, which can contribute into cartilage degeneration. Understanding cartilage stress is important for a better understanding regarding the influence of interventions.
According to this study, patellofemoral contact forces, contact area, and contact pressure magnitudes exhibited similar temporal variations over stance, all peaking in mid-stance. Patellar contact forces generally includes a medially directed component, which resulted in the patella pressure being more concentrated on the lateral facet.
Step rate significantly affected peak contact force magnitudes. Increased step rate induced a 16.6% lower patellofemoral force. The effects of an increased step rate also changed the medial component of the patellofemoral force. Step rate modification is an attractive option given that is easily trainable via auditory cues and can induce notable changes in loading patterns.
An increasing step rate (i.e. shortening step length) can effectively decrease cartilage contact area and the peak and average cartilage contact pressures that arise in mid-stance. It can also reduce knee energy absorbtion, with the latter effect primaraliy due to running with a more extended limb.
The vastus medialis strength did not affect pressure magnitudes, but did shift the location of contact pressure medially on the patella.
> From: Lenhart et al., J Biomech 48 (2015) 8. All rights reserved to Elsevier Ltd.. Click here for the Pubmed summary.