The main aim was to compare the kinematic deficiencies associated with each of the three main clinical phenotypes diagnosed by a clinical expert. The secondary aims were to compare neuromuscular postural and proprioceptive deficiencies associated with each of the three phenotypes.
Comparative non randomized study. We used the KneeKG device (EMOVI) to assess 3D knee rotations during gait using a treadmill, EOS Imaging to assess femorotibial alignment and an isokinetic device to measure hip abductor, quadriceps and hamstrings muscle strength and endurance. Unipodal static and dynamic stability were assessed with the Y test and posturography. We performed Kruskal-Wallis test (Dwass-Steel as post-hoc test) and Statistical Parametric Mapping, p0.05.
We included 45 participants: 29 (64.4%) females, the mean (SD) age was 36.3 (13.7) years, BMI: 22.9 (3.8) kg.m-2, symptom duration 8.1 (9.6) years and maximum VAS score 32.4 (26.9)/100. Four participants were classified in the PC1 group, 24 in PC2, and 9 in PC3; 6 were classified in both PC1 and PC2 (forming PC4). The increase in knee valgus during the loading phase (0 to 20% of the gait cycle) showed a significant difference between phenotypes [PC1: 0.3 (0.4)°, PC2: 2.1 (1.9)°, PC3: 0.5 (0.6)°, and PC4: 2.1 (2.0)°, (p=0.02)]. The post hoc analysis showed significant differences between all groups, except between groups 1 and 4 (p = 0.974). No other parameter differed significantly between phenotypes.
This is the first study to compare biomechanical parameters of participants with PFPS according to a pragmatic clinical classification. This study showed that the phenotype defined by extra-patellar alignment problems had the largest number of participants. Increased knee valgus during the gait loading phase was the only kinematic parameter differentiating clinical phenotypes. The lack of other significant differences could be explained by the sample size, the distribution of participants in the phenotype groups, and the classification used.
Insufficient understanding of the parameters contributing to the syndrome explains the lack of rehabilitation efficacy and the chronicity and/or recurrence of the pathology.
This study highlights the need for greater knowledge of the different forms of PFPS. A better understanding of the biomechanical, postural and neuro-motor parameters contributing to PFPS should allow the implementation of more specific and effective rehabilitation programs.
Kinematics assessment
patellofemoral pain syndrome
