Is there a correlation between isometric muscle strength and the kinematics of the pelvis, hip and knee during functional tasks in women with patellofemoral pain?

OBJECTIVES: To evaluate the correlation between isometric muscle strength of the hip abductors (HABD) and lateral rotators (HLR) with the range of motion (ROM) of the pelvis/hip in the frontal/transverse planes, respectively, and between the strength of the knee extensors (KExt) with the ROM of the knee in the sagittal plane during seven tasks. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Thirty-five women with patellofemoral pain. MAIN OUTCOME MEASURES: Maximum isometric muscle strength of the HABD, HLR, and KExt was measured using a manual dynamometer, and pelvis and lower limbs kinematics were evaluated using 3D optical system during gait, ascending and descending stairs, the forward and lateral step down tests, and the propulsion and landing phases of the single leg hop test (SLHT). RESULTS: A weak correlation was found between KExt strength and knee ROM in the sagittal plane (p = 0.05; r = -0.33) during SLHT landing, and a moderate correlation between HABD strength and ROM of pelvic obliquity (p < 0.01; r = 0.50) during ascending stairs. CONCLUSIONS: The lower strength of KExt has a weak correlation with higher knee flexion during the landing phase of the SLHT, and the lower strength of HABD has a moderate correlation with lower pelvis ROM in the frontal plane when ascending stairs.

Correlation of pain sensitization with muscle strength and angular kinematics in women with patellofemoral pain.

BACKGROUND: Patellofemoral pain has a poor long-term prognosis, which can be explained by a pain sensitization process. The pain sensitization process may be related to the increase of stress in the patellofemoral joint that is already associated with kinematic alterations and weakness in the musculature of the hip and knee. METHODS: Were compared the pressure pain threshold, temporal summation, conditioned pain modulation, angular kinematics, and muscle strength between 26 patellofemoral pain and 24 asymptomatic women and then correlated pain sensitization variables with biomechanical variables in pain group. The pressure pain threshold was determined on seven points of the knee, tibialis anterior muscle, and elbow. Ten consecutive stimuli were performed for temporal summation, and cold water was used as the conditioning stimulus for conditioned pain modulation. The strength of hip and knee muscles was determined using a manual dynamometer. Three-dimensional kinematics were evaluated during the lateral step down, considering peak and excursion values of the movement and the Movement Deviation Profile. FINDINGS: The pressure pain threshold of the elbow (2.13 [1.84-2.41] vs. 1.63 [1.25-2] kg/cm2), all sites of the knee were lower, as well as the Movement Deviation Profile was higher (9.33 [9.20-9.46] vs. 12.43 [12.1-12.75]) in the pain group. No difference in temporal summation, conditioned pain modulation, muscle strength and discrete kinematic values were found. No significant correlation was found between the Movement Deviation Profile and pressure pain threshold. INTERPRETATION: Biomechanical factors, pain processing, and modulation in women with patellofemoral pain, when different from asymptomatic individuals, are not necessarily associated.

Women with patellofemoral pain show altered motor coordination during lateral step down.

Patients with patellofemoral pain (PFP) present altered activation of the hip and knee muscles. Electromyography (EMG) analyses in PFP patients are usually performed individually for each muscle. However, several studies suggest that the central nervous system may modulate neural commands directed to groups of co-activated muscles, called muscle synergies. Investigating the synergistic organization in PFP will advance our knowledge of the influence of pain on muscle coordination. This study aimed to compare the motor coordination between women with and without PFP during the lateral step down (LSD). 15 women with PFP and 14 asymptomatic women underwent three-dimensional kinematics and EMG assessment during LSD. The Movement Deviation Profile (MDP) was calculated from kinematic data. Muscle synergies were extracted from EMG data of eight lower limb muscles using a non-negative factorization algorithm. Results revealed differences in MDP and an altered synergistic control between women with PFP and asymptomatic while performing the same motor gesture. Particularly, the variability accounted for (VAF) when using 3 synergies to reconstruct EMGs of the PFP group was higher than in the control group, suggesting reduced complexity of motor control in PFP. Detailed synergy analyses highlighted specific differences between groups in vastii and rectus femoris, which are muscles with a crucial role during the squat phase and the transition to rise phase of the LSD. This study shows the ability of muscle synergies analysis to reveal impaired motor coordination in PFP patients, and has the potential to be explored as a complementary tool to current clinical assessment techniques.

Step down tests are the tasks that most differentiate the kinematics of women with patellofemoral pain compared to asymptomatic controls.

BACKGROUND: Studies evaluating kinematics lead to different conclusions, not all changes appear in all assessed tasks and in all subgroups of patients with patellofemoral pain (PFP). The inconsistencies between studies could be reduced if we knew which task separates patients best from healthy controls. RESEARCH QUESTION: Identify which functional task, between gait, forward step down (FSD), lateral step down (LSD), stair ascent and descent and propulsion and landing phase of the single leg hop test (SLHT), differentiates the three-dimensional kinematics of women with patellofemoral pain from asymptomatic women. METHODS: This cross-sectional study evaluated thirty-five PFP and thirty-five asymptomatic women during the execution of the following tasks: gait, FSD, LSD, stair ascent and descent and the propulsion and landing phase of single leg hop test. Frontal, sagittal and transverse plane angles of the trunk, pelvis and hip, frontal and sagittal plane angles of the knee, ankle dorsiflexion, foot progression angle and hindfoot eversion were analyzed through the Movement Deviation Profile (MDP). To compare the groups, the multivariate analysis with Bonferroni post hoc test were used, with a significance level of p < 0.01. To identify which task presented the most difference between the groups, the Z-score of the mean MDP was calculated. RESULTS: For all tasks, the groups presented significant differences. According to the Z-score, the groups got farther apart considering the MDP for each task in the following order: LSD (7.97), FSD (7.62), landing phase of SLHT (3.43), gait (2.85), propulsion phase of SLHT (1.64), descending stairs (1.63) and ascending stairs (1.00). SIGNIFICANCE: We suggest that step down tests should be included in the assessment of PFP patients, since these tests most differentiate the kinematics of women with and without PFP. Identifying the tasks with the highest sensitivity to detect the kinematic differences is expected to improve clinical decision-making.