Differences in squat and stair descent lower limb kinematics between healthy controls and patients with patellofemoral pain

INTRODUCTION:

Patellofemoral pain (PFP) is one of the most common knee conditions that physiotherapists and physicians have to confront and has various aetiologies. To assess PFP, functional tests such as the squat and stair decent are routinely performed by clinicians (3). Little information exists, however, on the quantitative differences between healthy and PFP patients’ movement patterns when executing these tasks, especially as neuromuscular activation may differ due to PFP (4).

METHODS:

Ten healthy controls (age: 29.0 ± 6.6 years, height: 1.71 ± 0.11 m, body mass: 78.7 ± 16.32 kg, females: n = 5) and 10 PFP patients (age: 34.0 ± 9.1 years, height: 1.72 ± 0.09 m, body mass: 77.4 ± 18.9 kg, females: n= 5, referred by a consultant or general practitioner to NWW NHS physiotherapy department were recruited in this study. They performed a one leg hopping-landing-self-selected squatting task and a three-step descent task starting with the unaffected leg. 3D motion analysis was used to examine quadriceps angle (QAngle), knee flexion (KF), foot supination (FS), anterior and posterior pelvic rotation (PR_ASIS and PR_PSIS, respectively), and forward and backward pelvic tilt (PT_FWD and PT_XY, respectively) during execution of the squat or stair decent. Statistical Parametric Mapping (SPM) was used to compare the normalised kinematics time-series between controls and ACL patients for all the above variables and both tasks. Additionally, a 2 (group) x 2 (task) compared the maximum angle for QAngle KF and FS, followed with Bonferroni-corrected pairwise comparisons, where differences were revealed.

RESULTS:

SPM revealed no changes in squat normalised kinematics time-series for QAngle, FS, and PT_FWD. KF differed significantly (p < 0.05) between 18-20% of the movement range, PR_ASIS between 0-32% and 35-100%, PR_PSIS between 0-20% and 78-100% and PT_XY between 4-12%. For stair decent, no significant differences were revealed for any variables. Finally, no differences were revealed for maximum angle for QAngle and FS. KF revealed a significant difference for task only, with a 48.2° higher knee flexion for squat (p = 0.001).

CONCLUSION:

Our results suggest that discrete values from the functional tests used to assess PFP are unlikely to show differences between healthy and PFP patients. Similarly, the movement pattern of the stair decent is not affected by PFP, with only the squat showing such differences between groups. These findings contribute to understanding of PFP assessment, while support calls for identification of more robust tests (1, 2) as well as for examinations of the full movement range rather than discrete values from it (5).

REFERENCES:

1) Cook et al., Physiotherapy, 2012

2) Nunes et al., Phys Ther Sport, 2013

3) Papadopoulos et al., Open Sports Med J, 2015

4) Rodrigues et al., J Electromyogr Kinesiol, 2022

5) Walker et al, J Biomech, 2020