LANDING ERROR SCORING SYSTEM (LESS)
A clinical tool used to assess jump-landing biomechanics.
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By Lukas Krondorf
24th Dec 17 | 6 min read
Contents of Article
First presented in 2009, the Landing Error Scoring System (LESS) is a clinical tool used to assess jump-landing biomechanics. It was developed to identify individuals at risk of anterior cruciate ligament (ACL) injury , and is performed with a subject completing a Drop-Vertical Jump (DVJ) whilst video recorded from two planes (frontal and sagittal) . Being an easier, faster, and cheaper field-based variant of a complete biomechanical assessment , it can be performed without expensive laboratory equipment.
Keywords: ACL injury, biomechanics, DVJ, ACL-screening
Despite the explosion of research on ACL injury during the last 30-years, the exact mechanism of injury is still not fully understood. However, a combination of internal (e.g. anatomic, hormonal, neuromuscular) and external factors (e.g. environment, footwear, ground, opposing players) may adequately explain the mechanism [8, 11].
The greatest strain on the ACL occurs during 3-dimensional knee loading, which includes a knee extension moment, proximal anterior tibial shear force, knee valgus/varus moment, as well as a rotational contribution . After ACL reconstruction, altered movement mechanics in jump-landing tasks are often apparent  and have shown to increase the risk of re-injury by 5-15 fold .
Focussing on particular movements that have been associated to ACL injury during landing tasks , such as valgus rotation at the knee joint, movements screens such as the LESS have been developed to identify athletes who may be at risk of sustaining an ACL injury .
The Landing Error Scoring System (LESS) is a relatively easy-to-use assessment tool to analyse the biomechanics of the lower extremities in a landing and jumping task. As a reliable clinical screening tool, it is described to offer the greatest value for the identification of individuals at risk of attaining non-contact ACL-injury . However, recent research has questioned its ability to identify those at-risk of ACL injury due to a lack of validity .
Based on a 19-point continuous scale (see FREE downloadable scoring sheet), the LESS assesses the positioning of the trunk and lower extremities at various stages through the Drop-Vertical Jump (DVJ) movement. Global fluidity and range of motion in the landing phase are analysed from frontal and sagittal plane video data. Movement patterns deviating from the ‘biomechanical optimum’ can possibly predispose an athlete to lower-extremity injuries . Those are scored as “error-points”, and add up to a LESS score. Poor landing technique is indicated by higher LESS scores (more “error-points”) and vice versa.
As mentioned above, it is important to assess movement patterns that may predispose an athlete to ACL injury. As such, the LESS offers an accurate and inexpensive assessment of these movement concerns. Athletes’ identified as ‘at risk’ can then be directed towards specific training programmes designed to improve jump-landing mechanics in an attempt to reduce their risk of ACL injury.
Having said this, recent research assessing the effectiveness of the LESS for identifying ACL injury risk concluded it had limited predictive ability . This also lies in the generally low sensitivity and specificity of screening methods to this day. It might be wishful thinking to try to predict future injuries in an otherwise healthy athlete . Movement screens cover just a small part of the ACL injury mechanism, most other factors cannot be screened for.
It is important to understand that whenever fitness testing is performed, it must be done in a consistent environment (e.g. facility), so that it is protected from varying weather types, and with a dependable surface that is not affected by wet or slippery conditions. If the environment is not consistent, the reliability of repeated tests at later dates can be substantially hindered and result in worthless data.
Figure 1 displays the test configuration for the LESS. This setup must be adhered to if accurate and reliable data is desired.
The subject stands on a 30-cm-high box half the body height away from the landing zone marked by a line on the ground. The subject is then instructed to jump forward so that both limbs leave the box simultaneously aiming to land just past the line, and then jump for maximal height immediately after landing.
Video 1 demonstrates how the LESS is conducted and analysed.
Subjects can practice until comfortable with the task. No comment or guidance is provided unless performance does not follow the instructions. Any comment or judgment from the tester could disrupt the athlete’s performance and bias the test results. Three trials should be recorded by two off-the-rack video cameras that are installed; one recording the subject from the front (A), and the other recording from the side (B). Each camera should be placed 3m away from the landing zone (Figure 1). The captured movement can then be evaluated at a later time.
Based on a 19-point continuous scale (see FREE performance sheet), the LESS assesses the positioning of the trunk and lower extremities at various stages throughout the Drop-Vertical Jump (DVJ) movement. Using the performance recording sheet, the 1-15 items are scored dichotomically by adding either 1 or 0 to the final scores. Only items 16 and 17 add values 0, 1 or 2 depending on joint displacement and overall impression, respectively. Therefore, a maximal score of 19 can be reached for exceptionally poor performances, while scores <5 are regarded as “good” assuming low-risk for ACL injury . [/av_textblock] [av_hr class='invisible' height='50' shadow='no-shadow' position='center' custom_border='av-border-thin' custom_width='50px' custom_border_color='' custom_margin_top='30px' custom_margin_bottom='30px' icon_select='yes' custom_icon_color='' icon='ue808' font='entypo-fontello' av_uid='av-2r6ysz' id='' custom_class='' admin_preview_bg=''] [av_textblock size='' font_color='' color='' av-medium-font-size='' av-small-font-size='' av-mini-font-size='' av_uid='av-ppihar' id='' custom_class='' admin_preview_bg='']
The LESS was correlated against the gold standard, that is 3-dimensional motion analysis , and showed that good to excellent inter-rater and intra-rater reliability can be obtained [18, 20]. LESS scoring of six items has “excellent” (84-100%) agreement with 3D motion analysis .
LESS scores may vary widely in young athletes and military populations upon which the LESS was developed [17, 20]. Clear cut-off values for LESS scores dividing low-risk groups from groups with higher risk of obtaining ACL injury are thus difficult to establish. Commonly used cut-off values range between 5-5.5 . This results in ‘labelling’ athletes as low-risk with LESS scores of between 0 and 5, while a high-risk group contains individuals with a LESS score of 5 or higher. More studies must be conducted in the active population before normative data can be established .
It is being questioned whether the DVJ (which is not often associated with ACL injury itself ) is optimally challenging the knee while at the same time offering a safe, controlled and reproducible screening environment. More work should be done to provide enough evidence that increased knee motion during the drop vertical jump landing task actually increases the risk for non-contact ACL injury . Generic bilateral landing tasks (such as the DVJ) have limited predictive ability. To detect high-risk landing postures, sport-specific movements that are associated with ACL injuries may be a more appropriate approach in determining the efficacy .
Repetitive screening is a big part of the job of a sports exercise and medicine clinician. Periodic health evaluations can show underlying pathologies and/or injuries, assess rehabilitation status and establish return-to-sport benchmarks for athletes . The utilisation of high-quality research tools to build an evidence base in sports exercise should focus on specific sports and relevant sub-groups (such as gender) , as well as on the topic of return-to-sport.
Despite its limitations, the LESS remains the instrument of choice in testing biomechanical behaviour to identify individuals with potentially ‘risky’ movement patterns. It is never the goal to expose athletes to high-risk tasks during testing. Even if it would offer a better predictability, it also increases analysis and time burdens with screening . The LESS is a method requiring minimal time and equipment (total set-up time per individual is under 5 min ), and, is, therefore, applicable for a wide community . All evaluated movement patterns in the LESS actually increase the risk of attaining ACL injury in 3D motion analysis .
While all these evaluations seem confusing or misleading, they can be distilled down to one simple advice:
Use the LESS if:
Don’t use the LESS:
Some coaches believe that reading one article will make them an expert on Performance Testing. Here’s why they’re wrong…
Performance Testing entails many, many topics. By choosing to simply read up on The Landing Error Scoring System and ignore the sea of other crucial Performance Testing topics, you run the risk of being detrimental to your athlete’s success and not realising your full potential.
To make you an expert coach and make your life as easy as possible, we highly suggest you now check out this article on The Multiple Single-Leg Hop-Stabilization test.
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Lukas Krondorf BSc in Physiotherapy
Lukas is a second-year master student in Exercise Physiology (M.Sc.) at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. He holds a B.Sc. Physiotherapy from Germany with a specialisation in sports medicine.
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