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The Landing Error scoring System (LESS) is an inexpensive clinical tool used to assess potentially high-risk movement patterns (“errors”) during a jump-landing maneuver.[1] First published in 2009, it was developed to identify individuals at higher risk for anterior cruciate ligament (ACL) injuries. [2] It evaluates lower extremity and trunk alignment in the frontal and sagittal planes using 2D video recordings during forward double-leg jump landings.
Intended Population
The LESS is used to identify the risk of non-contact injuries in athletes especially involved in sports with a lot of jumping and landing[1][3]. It is an useful screening tool to identify 'at-risk' athletes and then direct them towards the appropriate training programs. The LESS is also used to assist in deciding return to sport for patients that have undergone anterior cruciate ligament reconstruction (ACLR) surgery [4].
Method of Use
Make sure that the surface is not affected by wet or slippery conditions
Materials required are as follows:
Measuring tape
30 cm (12 inch) high platform/box
Target line (At a forward distance of half the subjects height)
2 cameras positioned at a height of 1 meter height. One camera is placed 3 metres in front of the landing area (frontal view) and the second camera is placed 3 metres to the side (sagittal view)
Athlete is provided a demonstration prior to their assessment
The individual stands on the 30 cm high platform and is asked to jump forwards at a distance of 50% of their height marked by a line on the floor
Immediately upon landing they were required to perform a maximal vertical jump, that is jumping as high as they could once they landed from the box
The movements are recorded by both cameras from frontal and sagittal planes for later video analysis.
This is repeated for three trials.
Interpretation:
The tool contains 17 items where the first 15 items carry a score of 1 each, whereas items 16 and 17 carry a maximum score of 2 each, giving a total maximum of 19 points.[2] A LESS score is the count of errors observed, where a higher score indicates poorer jump-landing technique and a lower score indicates better jump-landing technique[2]. The original performance categories are[2][5]:
Excellent: <4
Good: 4 - 5
Moderate: 5 - 6
Poor: >6
Note: A cut-off score of 5 is often used to distinguish between low-risk (<5) and high-risk (≥5) individuals. The generalisability of this cut-off to other other noncontact lower-extremity injuries remains uncertain, as further research is required to determine whether population-specific thresholds are warranted[6].
The overall LESS score has demonstrated good-to-excellent reliability across different metrics[6]:
Intrarater reliability: ICC 0.82–0.99
Interrater reliability: ICC 0.83–0.92
Intersession reliability: ICC 0.81
Validity
The overall LESS score shows good validity when compared against 3D motion capture, which is the gold standard for biomechanical analysis.[6] For individual items, validity ranges from moderate-to-excellent for the majority of factors associated with ACL injury risk.[6] Regarding diagnostic accuracy, the tool has shown a sensitivity of 86% and a specificity of 64% for predicting ACL injuries in youth soccer athletes.[6]
Clinical Utility
While the LESS is a functional and accessible tool, the current scientific evidence indicates that the predictive value of the LESS for ACL and other noncontact lower-extremity injuries remains uncertain[6]. Clinicians should also be aware of sex differences; females often demonstrate reduced hip and knee flexion and increased knee valgus during landing, which may influence score interpretation.[2]
Landing Error scoring System Real Time (Less RT)
Unlike the original LESS which requires video camera and replaying the tapes for scoring, the LESS-RT evaluates in real time through direct visual observation. It assesses 10 jump-landing characteristics over 4 trials with an additional trial to observe all 10 items[8]. The procedure is similar to original LESS. The raters evaluate specific motions at the feet, knees, and trunk across all these trials. [8]
In first trial, raters note stance width, the degree of foot rotation, and initial foot contact (ie, whether the feet landed symmetrically was observed in the trial 1 (item 1-3)
The second trial evaluates knee and trunk frontal-plane motion.(item 4-5)
For trials 3 and 4, viewed from the side.
The third trial assesses how participants landed from the jump (ie, toe to heel, heel to toe, or flat-footed) and knee sagittal-plane motion.(item 6-7)
The fourth trial evaluates trunk sagittal-plane motion (item 8)
LESS-RT items 9 and 10 observe overall impression of total motion across all 4 trials of the jump-landing task.[8]
LESS-RT has shown good interrater reliability ranging from 0.72 to 0.81, and it is a quick and reliable clinical assessment tool to identify individuals at higher risk for lower extremity injuries[8].
Modified Landing Error Scoring System (LESS-M)
The LESS primarily detects movement errors during forward double-leg jump landings, while single-leg landings subject the lower extremity to higher vertical ground reaction forces. Landing direction impacts knee flexion excursion and angular velocity, with lateral landings (90°) showing poorer coordination compared to forward (0°) and diagonal (30° and 60°) landings[9]. Most non-contact ACL injuries occur during single-leg landings, and athletes post-ACL reconstruction exhibit altered load distribution during these landings[9][10]. Therefore, lateral single-leg jump landings may be effective for assessing knee injury risk in both healthy individuals and those with knee dysfunction.[9] The LESS-M involves a reduced item set (typically focusing on 10-12 key biomechanical markers) to allow for quicker assessment with participant are asked to perform a lateral (90° direction) single-leg jump landing from a 30-cm-high box. Research suggests it maintains a high correlation with the original 17-item scale, though specific cut-off scores for injury risk may vary depending on the specific modifications used.[9]
