Research Article Open Access
A Preliminary Investigation to Establish the Criterion Validity of a Qualitative Scoring System of Limb Alignment during Single Leg Squat and Landing
Lee Herrington1* and Allan Munro2
1 Senior Lecturer in Sports Rehabilitation, Directorate of Sport, Exercise and Physiotherapy, University of Salford, UK
2 Lecturer in Sports Rehabilitation, Division of Rehabilitation Studies, University of Bradford, UK
*Corresponding author: Lee Herrington PhD MCSP, Directorate of Sport, Exercise and Physiotherapy, Allerton Building, University of Salford, Manchester M6 6PU, United Kingdom, Tel: 00441612952326; Fax: 00441612952395 E-mail: @
Received: 05 April, 2014; Accepted: 04 July, 2014;; Published: 09 July, 2014
Citation: Herrington L, Munro A (2014) A Preliminary Investigation to Establish the Criterion Validity of a Qualitative Scoring System Page 5 of 6 of Limb Alignment during Single Leg Squat and Landing. J Exerc Sports Orthop 1(2): 1-6.
Abstract Top
Objective: The present study aimed to investigate the criterion validity of a novel qualitative assessment scheme to assess limb alignment during single leg loading activities.
Design and setting: Observational laboratory study
Main outcome measures: Performance of 5 participant’s single leg squat and hop landing was assessed using 3-D motion capture and the findings of this compared to the qualitative scoring scheme.
Conclusion: The scores generated by the qualitative scoring scheme used showed excellent association with the corresponding data from 3-D motion capture, implying the measurement tool shows criterion validity.
Results: The range of percentage of agreement between the qualitative and 3-D score was for all subjects across both tasks 95.6- 100%. The kappa measure of agreement was k = 0.9 for hop landing and k = 0.97 for single leg squat.
Keywords: Assessment; Lower limb; Movement
Introduction Top
The presence of abnormal dynamic alignment of the lower limb has been associated with numerous lower limb pathologies [1,2]. Within the literature limb alignment control has been assessed using what has been regarded as the “gold standard” 3-D motion capture [2]. These systems although accurate are expensive and assessments time consuming [3], this has led a number of authors to develop qualitative means of assessing lower limb alignment [1,3-7]. The findings of those studies have shown their scoring systems to be both reliable [1,3-7] and valid [3,5] and thus show considerable promise when assessing patients. To date these qualitative scoring systems have either assessed bilateral drop jumps [3,5,8] or single leg squatting [1,5,7], with none assessing single leg landing tasks or using a single system to assess diverse tasks. Ekegren, et al. [5] and Onate, et al. [3] both established the criterion validity of a qualitative scoring scheme (comparing with 3-D motion capture) of drop jump landing, however, no study to date has established the criterion validity of any qualitative scoring system for single leg tasks.
The purpose of this study was to undertake preliminary work to examine the level of agreement and validity of a novel observational movement assessment score and its ability to evaluate trunk and lower limb alignment during two different single leg loading tasks compared to 3-D motion capture. The aim being to assess the validity of the qualitative score acquired during single leg squatting and hop landing against 3-D kinematics.
Method
Subjects
The performance of five participants during single leg squat and single leg landing tasks was assessed using 3-D motion assessment and a qualitative scoring system. This group comprised of three male and two female subjects (mean age 20.6 ± 1.3 years; height 1.78 ± 0.1 m; weight 78 ± 7 kg) who gave written informed consent to participate and the project was approved by the host university research and ethics committee. All participants were physically active, participating in at least 3 hours training per week and had no current or previous (in the last 2 years) lower limb, low back or pelvic injuries.
Procedures
Single leg squat test (SLS) task: Participants were asked to take a single leg stance on the force plate, then to squat to at least 45° knee flexion and no greater than 60°, over a period of five seconds. Knee flexion angle was checked during practice trials using a standard goniometer (Gaiam-Pro) then observed by the same examiner throughout the trials. There was also an electronic counter used to mark the five second period with the first count initiating the movement, the third indicating the lowest point of the squat and the fifth indicating the end. Trials were only accepted if the participant squatted within the desired range of knee flexion [9]. Data was collected from three trials which met the inclusion criteria.Single leg landing (SLL) task: Participants dropped from a 30 cm step, standing on the leg to be tested (right in all cases), participants were instructed to hop and land on a mark 30 cm in front of the step on the force platform. Participants had to ensure the contralateral leg made no contact with any other surface. Participants were required to hold the landing for at least two seconds before stepping off the force plate. Trials were only accepted if the subjects landed on the mark and held the position for 2 seconds [9]. Data was collected from three trials which met the inclusion criteria.
3D analyses:A twelve-camera OQUS (Qualisys, Gothenburg, Sweden) motion analysis system sampling at 100 Hz, and a force platform (AMTI BP400600, USA) sampling at 1000 Hz, was used to collect the kinematic data. Prior to testing reflective markers were attached to the participants at the anterior superior iliac spines, posterior superior iliac spines, iliac crest, greater trochanters, medial and lateral femoral condyles, medial and lateral malleoli, posterior calcanei, and the head of the first, second and fifth metatarsals. These markers were used to define the anatomical reference frame and centres of rotations of the joints. Five rigid plates, each consisting of four non-collinear markers, were secured with elastic bandages on the anterolateral aspect of the thigh, shank and around the pelvis. These rigid bodies were used as tracking markers to track the movement of each segment during the movement trial. The use of a rigid marker set of four non-collinear markers for tracking purposes has previously been shown to be the optimal configuration in comparison to using individual skin markers and other rigid arrays [10]. To track the motion of the thoracic spine, a rigid plate with three attached markers, was attached to the sternum and in order to define an anatomical reference frame for this segment, markers were attached to C7, the spinous process of the sixth thoracic vertebra (T6), the suprasternal notch and the xiphoid process. The calibrated anatomical systems technique (CAST) was employed to determine the movement of each segment and anatomical significance during the movement trials [11]. A static trial was carried out initially to allow for later identification of the anatomical and tracking markers in the Qualysis software prior to extraction to post-processing software and define the subjects neutral (anatomical) zero position which are referred back to this position. Post-processing calculation of the kinematic and kinetic time series data was conducted using Visual3D motion capture software (Version 4.21, C-Motion Inc., Rockville, MD, USA). Motion and force plate data were filtered using a Butterworth 4th order bi-directional low-pass filter with cut-off frequencies of 12 Hz for kinematic data and 25 Hz for force plate data. Three trials were recorded and mean data from the three trials of each task was used for comparison to the qualitative score.
Qualitative assessment: Qualitative assessment of the two tasks was made from digital video footage captured simultaneously during the 3D assessment. A digital video camera (Sony Handycam DCR-HC37) sampling at 25 Hz was wall mounted at a height of 60 cm and 10 metres away from the force plates. Digital video footage was recorded at a standard 10x optical zoom throughout each trial in order to standardize the camera position.
A qualitative scoring system was devised by the primary author (LH) based on the previously reported scoring systems of Crossley, et al. [1] and Whatman, et al. [3]. It involved dichotomous scoring of the movement strategy occurring in individual body regions (arm, trunk, pelvis, thigh, knee, foot). Scoring was defined as a zero for appropriate strategy and one for inappropriate movements, for each region with best overall score being 0 and worst 10 points. The scoring sheet is shown in Table 1. Typical errors are shown in Table 2. Optimal behaviour involved minimal deviation or body movement from that prescribed, that is arm do not move, trunk is slightly flexed, but held still, pelvis stays in mid position with minimal tilt, thighs stay parallel and approximately vertically orientation, patellae point towards middle of foot and foot demonstrates minimal wobble.
Analysis: A single examiner (LH) (blind to 3-D data) assessed the videos of the single leg squat and single leg landing of each subject; each video was viewed three times at standard speed and then scored using the qualitative scoring sheet. A second investigator (AM) then analysed the findings of qualitative assessment and compared them to those of the 3-D assessment. Prior to viewing the qualitative scores the same investigator (AM) reduced the 3-D kinematic data for each participant and each joint motion, into dichotomous scores (0=alignment/motion of segment/joint within range of normative data; 1= alignment/ motion exceeds range of normative data) corresponding to the movement individual segment movement strategy within the qualitative scoring sheet this reflected the method used by Onate et al. [3]. The normative range was based on those reported in the review of Fox et al. [12].
Statistical analysis: To assess the agreement between 3-D score and qualitative score, a kappa statistical analysis was used.
Table 1: Qualitative assessment form.

Qualitative analysis of single leg loading

Date:                                                               Patient:

Condition: Left                                              Right        Bilateral

QASLS

Task:  Single leg squat   Single leg step down  Single leg hop for dist

Left

Right

Arm strategy

Excessive arm movement to balance

Trunk alignment

Leaning in any direction

Pelvic plane

Loss of horizontal plane

Excessive tilt or rotation

Thigh motion

WB thigh moves into hip adduction

NWB thigh not held in neutral

Knee position

Patella pointing towards 2nd toe (noticeable valgus)

Patella pointing past inside of foot (significant valgus)

Steady stance

Touches down with NWB foot

Stance leg wobbles noticeably

Total

Table 2: Typical errors assessed with qualitative score.

QASLS category

Error

Optimal

Sub-optimal example

Arm strategy

Excessive arm movement to balance

Trunk alignment

Leaning in any direction

Pelvic plane

Loss of horizontal plane

Excessive tilt or rotation

Thigh motion

WB thigh moves into hip adduction

NWB thigh not held in neutral

Knee position

Patella pointing towards 2ndtoe (noticeable valgus)

Patella pointing past inside of foot (significant valgus)

Steady stance

Touches down with NWB foot

Stance leg wobbles noticeably

Table 3: Individual comparisons across scoring criteria.

Task

Criteria

Single leg squat

(SLS)

Arm

Trunk

Pelvis Frontal

Pelvis

Rotation

WB Hip

NWB

Hip

Knee

Valgus

minor

Knee Valgus

Major

WB

Excess motion

NWB

Touch

down

Participant

Gender

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

1

Male

0

0

0

0

0

0

0

0

1

1

0

0

0

0

0

0

0

0

0

0

2

Male

0

0

0

0

1

1

0

0

1

1

0

0

1

1

0

0

0

0

0

0

3

Male

0

0

1

1

1

1

0

1

1

1

0

0

1

1

1

1

0

0

0

0

4

Female

0

0

1

1

0

0

1

1

1

1

0

0

1

1

0

0

0

0

0

0

5

Female

0

0

1

1

1

1

1

0

1

1

0

0

1

1

1

1

0

0

0

0

Task

Criteria

Single leg land

(SLL)

Arm

Trunk

Pelvis Frontal

Pelvis

Rotation

WB Hip

NWB

Hip

Knee

Valgus

minor

Knee Valgus

Major

WB

Excess motion

NWB

Touch

down

Participant

Gender

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

Q

3D

1

Male

0

0

0

0

0

0

0

0

1

1

0

0

0

0

0

0

0

0

0

0

2

Male

0

0

0

0

1

1

0

0

1

1

0

0

1

1

0

0

1

1

0

0

3

Male

0

0

1

1

1

1

1

0

1

1

0

0

1

1

1

1

1

1

1

1

4

Female

0

0

1

1

0

0

1

1

1

1

1

0

1

1

0

0

0

0

1

1

5

Female

0

0

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

1

0

0

Q= Qualitative score 3D= dichotomised 3D motion capture variables score 0= alignment-motion-activity in optimal range 1= alignment-motion-activity outside of optimal range
Results Top
Single leg squat task
Average PEA across all cases between the qualitative and 3-D score was 98.4% (range 96.9-100%). There were differences in two subjects in scores between qualitative score and 3-D, whilst three showed perfect agreement. The disagreement was a single point for both of these subjects and the disagreement in both cases related to scoring of pelvic rotation (Table 1). The mean kappa measure of agreement across subjects was k = 0.97 (95% CI 0.86-1.00).
Single leg landing task
Average PEA across all cases between the qualitative and 3-D score was 97.1% (range 95.6-100%). There were differences in two subjects in scores between qualitative score and 3-D, whilst three showed perfect agreement. The disagreement was a single point for both of these subjects and the disagreement in one case related to scoring of pelvic rotation and in the other excessive non weight bearing thigh motion (Table 3). The mean kappa measure of agreement across subjects was k = 0.9 (95% CI 0.83-1.00).
Discussion Top
In this pilot study the qualitative scoring system used in this study was shown to have a strong relationship to the kinematic data generated using 3-D motion capture; this was in line with previous studies [3,5] which had examined the relationship of qualitative scoring systems during drop jumping tasks. No previous studies have examined criterion validity of a qualitative scoring system during a single leg loading tasks (single leg squat, single leg hop landing) so comparison to these tasks are not possible.
The qualitative scoring system used was based on those previously reported in the literature which had attempted to analyse single leg squat and had shown good to excellent intra and inter tester reliability.[1,7] The scheme incorporated the region criteria similar to that used by both Crossley, et al. [1] and Whatman, et al[7], following the assertion from both Onate, et al. [3], Chmielewski, et al. [4] and Whatman, et al. [7] that this increased content validity. Similarly, a dichotomous scale was used when classifying motion within each of the regions which was shown to increase reliability [7]. The scheme used in this study was modified from those studies to also take into account trunk motion which Crossley, et al. [1] and Myer, et al. [6] regarded as a significant factor in the alteration of lower limb moments.
Conclusion Top
Many authors regard 3-D motion analysis as the “gold standard” for assessing dynamic lower limb alignment control [2,3,8] but this is not an option open to most clinicians. The qualitative assessment scheme used in this pilot study has been shown to have strong criterion validity when compared to 3-D motion capture, so may provide an alternate means of assessing dynamic lower limb alignment control for the clinician. Further work though is still required on the tool to assess its reliability and sensitivity to change, on a larger scale, before it is ready to be fully adopted.
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