Jump-Landing Mechanics Assessment Using Landing Error Scoring System in Athletes with and without Patellofemoral Pain:

Purpose: This study was a cross-sectional study that aimed to compare the total LESS scores of individuals with PFP with healthy controls and assess the association of pain, function, and psychological factors with LESS score. Methods: Twenty-seven male athletes with PFP completed a standardized jump-landing task. They were compared with a matched, healthy group. Also, participants completed four questionnaires involving the visual analog scale (VAS), Anterior knee pain scale (AKPS), fear of motion (TAMPA), beck anxiety and depression inventory scale (BAI, BDI). Results: PFP group had a higher total LESS score than the control group signi�cantly. They had errors when landing with lateral trunk �exion and less knee �exion in the initial contact. Our results showed a signi�cantly strong correlation between VAS, AKPS, and TAMPA with a �nal score LESS. Also, a low to moderate signi�cant correlation obtained between BAI, BDI and �nal score LESS. Conclusions: The LESS is a useful clinical test for evaluating landing errors in people with PFP. Greater kinesiophobia, pain, poorer self-reported function and psychological factors was correlated with a total LESS score.


Introduction
Patellofemoral pain (PFP) is the most common lower extremity injury, which affects one in four athletes [1].They often report pain during activities that load the patellofemoral joint.PFP symptoms in athletes limit their sports activities and functional tests such as step down test, single-leg hop test, star excursion balance test [2,3].Risk factors for the development of PFP include increased Q angle, knee valgus, navicular drop, quadriceps weakness, excessive pronation, decreased knee exion, and increased hip internal rotation during the jump-landing task [4,5].Altered kinematics would exaggerate PFP patients' condition and increase their pain, thus examination of movement patterns is necessary.Threedimensional movement analysis measurement tools are powerful for the assessment of movement patterns, but they are not practical.Clinical tests are relatively easy to use and popular for the evaluation of balance, muscle imbalance, and faulty movement patterns.They are effective in screening subjects at injury risk [6].Detecting risk factors, and musculoskeletal problems using the them could help prescribe speci c exercises for the prevention of lower-extremity injuries in sports competitions.
Anteromedial lunge, step-down, single-leg press, bilateral squat, balance and reach are the functional tests that often are used in the evaluation of people with PFP, but they mostly have no speed and intensity.In addition, they provide no information about individual movement techniques [7].The Landing Error Scoring System (LESS) is a real-time quick clinical test to detect high risk movement patterns during a jump-landing task.It is a dynamic test to identify the quality of motion during jump-landing in athletes especially involved in sports with a lot of jumping and landing [8].A recent systematic review reported good reliability and concurrent validity LESS with 3-dimensional motion analysis in healthy people such as military freshmen, soccer players, and the recreationally active population [9].
Previous studies have shown altered kinematics of the PFPS group in comparison with the control group with motion analysis capture systems.They reported lower hip, knee and ankle excursion during singlelegged drop vertical jumps [10], greater hip-adduction excursion during single-leg jumps [11] and forward trunk lean in stair ascent/descent [12] but it is not clear if individuals with PFP perform differently on the LESS or higher errors on speci c LESS items than healthy controls; thus, rst the purpose of this study was to compare total LESS scores individuals with PFP and healthy controls.
Psychological factors negatively impact on athletic 'performance.A systematic review demonstrated anxiety, depression, catastrophizing and fear of movement are common in people with PFP [13].Also, association kinematic variables assessed by three-dimensional motion analysis system with functional status and pain level have been shown [14]; however, the association between psychological features, pain and disability with LESS is unclear in people with PFP.Thus, the second aim of this study was to examine the relationship between pain, functional status, and psychological factors with LESS score.

Method
Study design: This study was an observational cross-sectional study approved by the Ethics Committee of the *** (Approval number: ***).

Participants
Twenty-seven male athletes with PFP in any varsity sport were recruited through a sample convenience.
They included if they had ≥ 30 minutes of moderate or vigorous physical activity ≥ 3 times per week.A physical therapist diagnosed PFP subjects with the following criteria: report of anterior knee pain during at least two activities such as squatting, prolonged sitting, ascending or descending stairs, running, or jumping, also, pain in the patellar compression, tenderness in the posterior surface of patellar, or pain with resisted isometric quadriceps contraction.Subjects were excluded with knee trauma, previous knee surgery, patellar dislocations, ligament instability, meniscal tearing, back pain, hip pain and sacroiliac joint pain [15][16][17].The control group were matched by age,sex, BMI and activity level (Tegner scale) to the PFP athletics.All subjects signed informed consent before the entry of the study.

Procedures and outcomes:
Eligible participants completed a questionnaire involving demographic information.They also, ful lled visual analog scale, Anterior knee pain scale and fear of motion, anxiety, and depression questionnaires.
Pain intensity was measured using the 10 cm the visual analog scale ranging from 0 for no pain to 10 for the worst possible pain.Participants were asked to demonstrate the average intensity of the pain experienced in the patellofemoral joint in the past week on the visual analog scale [18].Tampa Scale of Kinesiophobia (TSK) short form was used to evaluate fear of movement.Participants are asked to score their level of agreement from 1 to 4. A higher score indicated higher kinesiophobia.** version of this questionnaire has been shown to have acceptable internal consistency and reliability in chronic musculoskeletal conditions.
Anterior knee pain scale (AKPS) was used to evaluate of symptoms and activities due to patellofemoral pain.It is a 13-items self-report questionnaire that has scores between zero and 100 points.Higher score indicated higher disability.Participants were asked to record limping when walking, giving load, walking, squatting, running, jumping, prolonged sitting with knee exed, pain, swelling, abnormal painful patella movements, and atrophy of thigh and exion de ciency.The acceptable level of ICC > 0.70 was reported for the ** version AKPS.
Beck Anxiety Inventory (BAI) was used for measuring the anxiety level of subjects.The BAI is a self-report questionnaire consisting of 21 items.Each item is on a four-point scale ranging from 0 (not at all) to 3 (severely).Thirteen of them describe physical symptoms (e.g., numbness or tingling), ve represent cognitive aspects of anxiety (fear of the losing control), and three have a physical and cognitive meaning (e.g., terri ed or afraid).We asked participants to rate items according to how much they are troubled by these symptoms.** version BAI had good reliability, validity, and excellent internal consistency.
The Beck Depression Inventory (BDI) was used to measure the presence and severity of depression symptoms.It is a 21-item self-report questionnaire that each item had a 4-point scale from 0 (symptom absent) to 3 (severe symptoms).We request participants rate items based on how much they had these symptoms two weeks ago.** version of BDI has high internal consistency and acceptable test-retest reliability.
After this, subjects were familiarized with the drop-jump task.The task involves a participant jumping forward with standardize footwear from a 30-cm-high box at a distance of half the subject's height away which have been marked on the oor, and immediately jumped vertically as high as they could.Participants were instructed to start the jump in a neutral position, standing feet shoulder width apart.They did not receive any feedback about landing techniques.Each subject performed 3 trails with 1minute rest period between them.Tests were recorded using 2 video cameras (Sony H.D.) in frontal and sagittal view.Two examiners evaluated movement patterns at the feet, knee, hip and trunk during each trial.They were blind to each other's scoring.The nal LESS scores were calculated on 17 different items.
Items were demonstrated in Table 2. Scores are categorized into excellent (LESS score ≤ 4), good (LESS score ≥ 4 to ≤ 5), moderate (LESS score > 5 to ≤ 6), and poor (LESS score > 6).A higher LESS score shows poor technique and a lower LESS score better jump-landing technique.Two raters independently scored Less for inter reliability.One of the raters viewed videos 6 weeks later and scored them for intra reliability.

Statistical Analyses:
Intraclass correlation coe cient (ICC) with 95% con dence intervals was used to assess interrater and intra reliability of the LESS nal composite score.ICC values greater than 0.9 show excellent reliability, values between 0.75 and 0.9 were considered good reliability, 0.50 to 0.75 show moderate reliability, and values below .50 are provided as poor reliability [19].Independent t-test and Mann-Whitney U test was used to examine differences in total LESS score and demographic Information between two study groups.The normality of data was assessed using the Shapiro-Wilk test.The Fisher exact test (FET) was used to determine the frequency of errors on each LESS item.The Pearson and spearman correlation coe cients were used in order to test the associations between VAS, AKPS, TAMPA, BAI and BDI with a nal score LESS.The level of signi cance for all statistical tests was set at p < 0.05.All data analysis was analyzed using SPSS software.The sample size of this study was determined using G*Power, Version 3.1.9.7, (Franz Faul et al., Universit€ at Kiel, Germany).24 people for each group were determined with 85% power, effect size 0.8 and type I error a = .05.

Results
The demographic and clinical features of the subjects are presented in Table 1.Means and standard deviations for total LESS for raters 1 and 2 were respectively 6.13 ± 2.05 and 7.51 ± 2.15.For the total score of the LESS, the ICC2, for interrater reliability were 0.62 (95% con dence interval = 0.54-0.93;P > 0.001) and the ICC2, for intrarater reliability was 0.91 (95% con dence interval = 0.86-0.94;P > 0.001).
The reliability of a clinical test is critical for utilization in the clinical and research settings.Our result found acceptable intrarater and moderate reliability for nal score LESS for PFP athletics.LESS scores of the PFP athletes who participated in the test-retest reliability was compared with healthy athletes.The independent samples t-test showed the PFP group had signi cantly a higher total LESS score than the control group (PFPS: 7.51 ± 2.15 errors; control: 3.18 ± 2.67 errors; P < 0.01).The Fisher exact test (FET) showed PFP group receive an error for Knee-exion angle at initial contact and lateral trunk exion items in comparison with healthy athletics controls and overall impression (Table 2).Relationships between pain, disability and psychological features with a nal score LESS was presented in Table 3.The result this study showed a signi cant strong correlation between VAS, AKPS and TAMPA with nal score LESS.Also, a low to moderate signi cant correlation obtained between BAI, BDI with nal score LESS (Table 3).

Discussion
The primary objective of this study was to determine whether total LESS score was different in athletics with patellofemoral pain and healthy subjects.Results of this study showed total LESS score was signi cantly greater in the PFPS group in comparison with controls.These ndings showed that individuals with PFP had higher errors and different strategies in the landing task compared with the controls group.These results were due to receiving errors for knee exion in the initial contact and lateral trunk exion during landing.Decreased knee exion may be a strategy for PFP people by reducing compressive loads associated with knee exion to protect the patellofemoral joint [10].Lateral trunk lean toward the involved side during landing could be a compensation mechanism due to reduced core stability [20],and decreased eccentric strength of the hip abductors in PFP people [21].The trunk and hip stabilizers pre-activate to counterbalance trunk motion and regulate lower extremity postures.Reduced pre-activation of the trunk and hip stabilizers may allow increased lateral trunk positions that can increase knee valgus loads [22].These ndings are in agreement with previous researchers that utilized motion analysis to examine the kinematic differences between PFP and healthy control groups.

Limitation
This study has some limitations.First, participants in this study were male athletic with PFPS; thus, the result of this study could not be generalized to the total population with PFP.Second, this was a crosssectional study that could not establish a cause-and-effect relationship between the psychologic factors, pain, disability and physical function.It suggests future studies design a longitudinal study to examine them.

Conclusion
Our results demonstrated individuals with PFP had higher total LESS scores than control groups.The LESS may be a useful clinical tool in assessing motion; and identifying potentially high-risk movement patterns during a jump-landing athletic with PFP.Greater kinesiophobia, pain, poorer self-reported function, and psychological factors were correlated with LESS score.

Table 2 Common
Errors of LESS between groups:

Table 3
Correlation results of pain,AKPS,BAI,BDI and LESS score in the patellofemoral pain group [3]]s et al. reported PFP group had lower knee excursion during single-legged vertical jump compared to the control group[10].Willson et al. observed trunk lateral-exion force more than the control group during single-leg squats in individuals with PFP [23].Curico dos Reis et al. demonstrated greater trunk lean, and less hip and knee exion during a single-leg triple hop test in individuals with PFP [24].Paoloni et al. single leg squat hip adduction, step-down knee abduction, jogging knee abduction, and jogging hip adduction [26].Also, De Oliveira Silva et al. showed Kinesiophobia is highly correlated with altered movement during stair descending in individuals with PFP[27].Selhorst et al. demonstratedan association between Fear avoidance beliefs and the Tampa Scale for Kinesiophobia with pain, selfreported function (AKPS), lateral step-down and single leg hop for distance test[28].Inconsistent with our results, Priore et al who found no association between Kinesiophobia and pain catastrophism with functional tests consisting of step-down, single-leg hop and modi ed star balance that it could be due to difference in populations study(women with PFP vs athletics PFP ) and type of functional tests[3].However, to the best of our knowledge, this is the rst study that assesses the association of psychologic factors with an objective functional test in athletics with PFP.
[25]rted decreased knee extensor moment in loading response and terminal stance gait cycle in normal walking in PFPS[25].The other result of this study were a signi cant strong correlation between VAS, AKPS and TAMPA and a low to moderate correlation between BAI, BDI with a nal score LESS.In agreement with our ndings, Glaviano reported a signi cant and moderate relationships between fear avoidance belief with functional tests involving