Are there differences in Knee Stability between Patients with Patellofemoral Pain and Healthy Subjects during a Slow Step Descent Task?

Abstract

Objective: To date no study exists to determine whether knee kinematics in the coronal and transverse planes during step descent are different between healthy subjects and patients with patellofemoral pain (PFP) despite patients often reporting pain and instability during this task. This study investigated the differences in knee kinematics between healthy subjects and patients with PFP during a step descent task.
Methods: Thirty healthy subjects and 29 patients diagnosed with PFP performed a slow step descent from a 20cm step. Kinematic data were collected using a ten camera infra-red motion analysis system. Reflective markers were placed on the foot, shank and thigh using the Calibrated Anatomical Systems Technique (CAST).
Results: The coronal plane knee range of motion was 2.7 degrees, 41% greater, in the PFP patients compared to healthy subjects (p=0.006), with 4 degrees greater internal rotation although this was not significant (p=0.087). A trend towards significance was also seen between males and females (p=0.059), with females having a greater range of motion in the transverse plane than both the healthy subjects and male patients, with females with PFP showing the greatest range of motion.
Conclusions: This study further reinforces the view that coronal plane mechanics should not be overlooked when studying PFP. Future research should focus on developing more clinically viable techniques that can provide clinicians with reasonable estimates of coronal plane knee kinematics during various functional tasks, this may help identify important clinical subgroups and responders and non-responders to different interventions.