Effect Of Arch Height On Lower Limb Kinematics And Muscle Function In Patients With Patellofemoral Joint Pain

Objectives: Patellofemoral pain,the most common type of injury in the knee joint,is clinically characterized by peri-patellar or posteriorfemoral pain,aggravated by activities like running,squatting,and stepping up and down steps.This chronic pain severely reduces the quality of life and level of physical activity.And it is a known precursor to patellofemoral arthritis.Therefore,it is very important to explore the risk factors related to the occurrence of PFP in order to achieve accurate prevention and treatment.Currently,more and more studies have paid attention to the distal risk factors related to PFP.Arch height,as one of the distal factors,is associated with a variety of lower limb injuries,but the relationship with PFP remains unclear.In this paper,the effect of arch height on biomechanical factors related to PFP patients was studied,and the relationship between the occurrence of PFP and arch height was exploredMethods: In this study,a total of 11 healthy subjects with normal Arch height and 40 patients with PFP were recruited.The Arch height index(AHI)of patients with PFP was divided into three intervals of the same width using the "range trichotomous method".Accordingly,PFP patients were divided into High arch height index group(HAG),Medium arch height index group(HAG),MAG),Low arch height index group(LAG),the AHI ranges of the three groups were 0.296≤AHI≤0.325,0.267≤AHI < 0.296,0.238≤AHI < 0.267,respectively.Arch height index was tested 3 times and averaged.Hip and knee kinematics,lower limb surface electromyography and maximum isometric muscle strength of hip and knee were collected for all subjects during ascending and descending steps,and the above indexes were collected three times respectively.Kinematic data were obtained using the mean value of the peak angles of each joint during the 3 tests.Surface Emg data was processed by Emg server.First,band-pass filtering with a frequency of 20-500 HZ was used,and then rectified.Root Mean Square(RMS)amplitude was analyzed,and corresponding MVC was used for standardization processing.The maximum isometric strength was used as the maximum value of the three tests,standardized using the subjects’ respective body weight.Results:Kinematics: When all PFP patients were compared to healthy groups,the peak values of hip adduction Angle(p < 0.05),hip internal rotation Angle(p < 0.05)and knee abduction Angle(p < 0.05)in the first and single bracing period of PFP patients were significantly higher than those in the healthy group and the second bracing period(p < 0.05)was significantly higher than that of the healthy group;The peak value of adduction Angle(p <0.05),internal rotation Angle(p < 0.05)and abductor Angle of knee(p < 0.05)in the single propping stage of the gait cycle of PFP patients were significantly higher than those in the healthy group and those in the first and second propping stages(p < 0.05)and internal rotation Angle(p < 0.05)More than the healthy group.Comparing HAG,MAG and LAG,it was found thatthe peak value of knee abduction Angle of LAG and MAG was significantly higher than that of HAG during the first pair of support period.In the single support period,the peak value of hip adduction Angle with LAG(p < 0.05)was significantly higher than that of HAG and MAG,and the peak value of knee abduction Angle with LAG and MAG(p <0.05)was significantly higher than that of HAG.LAG(p < 0.01)and MAG(p < 0.01)were significantly higher than HAG in the second double brace period.During the first pair of support period,the peak value of hip adduction Angle(p < 0.01)and knee abduction Angle(p< 0.01)of LAG and MAG were significantly higher than that of HAG,and the peak value of hip rotation Angle of LAG(p < 0.05)was significantly higher than that of HAG and MAG.In the single support period,the peak value of hip adduction Angle with LAG(p < 0.05)was significantly higher than that in HAG group,and the peak value of hip internal rotation Angle with LAG and MAG(p < 0.05)and knee abduction Angle with MAg(p < 0.05)were significantly higher than that in HAG group.In the second double support period,the peak of adduction Angle of hip with LAG(p < 0.01,p < 0.05)was significantly greater than that of HAG and MAG,and the peak of internal rotation Angle of hip with LAG and MAG(p < 0.01)and abductor Angle of knee with LAG and MAg were significantly greater than that of HAG.EMG: When all PFP patients were compared to healthy groups,the standardized RMS values of vastus medialis oblique,VMO/VL,rectus femoris and gluteus maximus in PFP patients were significantly lower than those in healthy group at the ascending step(p < 0.05),while the standardized RMS values of vastus medialis oblique,VMO/VL,vastus lateralis,gluteus maximus and gluteus medius in PFP patients at the descending step were significantly lower than those in healthy group(p < 0.05).The VMO/VL value of LAG was significantly greater than that of MAG at the upper step(p < 0.01),and the VMO/VL value of LAG at the lower step was significantly greater than that of HAG and MAG at the lower step(p < 0.01).Maximum isometric strength: When all PFP patients were compared to healthy groups,the maximum isometric strength of knee extension(p < 0.01),hip extension(p < 0.01),hip abduction(p < 0.01)and hip external rotation(p < 0.01)in PFP patients were significantly lower than those in healthy group.There were no significant differences in the maximum isometric strength of each joint among PFP patients with different arch heights(p > 0.05).Conclusions:(1)Patients with PFP showed abnormal movement patterns of excessive hip adduction,excessive hip pronation and excessive knee abduction during the upper and lower step gait cycles;In PFP patients,the activation level of lower limb related muscles decreased and the maximum isometric strength of hip and knee joints was insufficient when ascending and descending steps,reflecting the neuromuscular control disorder of lower limb in PFP patients.(2)Compared with HAG,LAG and MAG show more abnormal action patterns when they are in the upper and lower steps,and the abnormal action pattern of LAG is the most serious.The activation levels of VMO and VL in HAG and MAG were unbalanced,while those in LAG were more balanced.HAG,MAG and LAG showed no significant difference in maximum isometric strength of hip and knee.This suggests that arch height may increase the risk of PFP by changing the hip and knee kinematics,especially the risk of PFP is higher in people with low arches,and the imbalance of VMO and VL activation level may not be a risk factor in people with low arches.