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Single-Leg Squat as a Tool to Evaluate Young Athletes' Frontal Plane Knee Control

Räisänen, Anu MHSc; Pasanen, Kati PhD; Krosshaug, Tron PhD; Avela, Janne PhD; Perttunen, Jarmo PhD; Parkkari, Jari PhD

Clinical Journal of Sport Medicine: November 2016 - Volume 26 - Issue 6 - p 478–482
doi: 10.1097/JSM.0000000000000288
Original Research

Objective: To determine the agreement between 2-dimensional video analysis and subjective visual assessment by a physiotherapist in evaluating young athletes' knee control, and to determine the intrarater reliability and inter-rater reliability of the single-leg squat test.

Design: Frontal plane knee control was assessed by a physiotherapist on a 3-point scale. Frontal plane projection angles were calculated from video images. To determine the intrarater reliability, a physiotherapist reassessed 60 subjects' performances from a video. For the inter-rater reliability, 20 subjects were assessed by both the physiotherapist and a nonexperienced tester. The study continued for 3 test years.

Setting: Research institute.

Participants: Three hundred and seventy-eight floorball, basketball, ice hockey, and volleyball players.

Assessment of Variables: Knee control was assessed to be good, reduced, or poor.

Main Outcome Measures: Agreement between the video analysis and subjectively assessed frontal plane knee control. Intrarater reliability and inter-rater reliability.

Results: There were statistically significant differences in the mean frontal plane knee angles between subjects rated as having “good,” “reduced,” or “poor” knee control. Intrarater reliability was fair for the assessments in the first year, moderate (dominant leg) and good (nondominant leg) for the second year, and very good (dominant leg) and good (nondominant leg) for the third year. Inter-rater reliability was fair/poor.

Conclusions: This study suggests that by using the subjective assessment of the single-leg squat task, it is possible to detect differences in frontal plane knee control in young team sport athletes. The assessment can be considered to be reliable for clinical use when performed by an experienced tester.

*Tampere Research Center of Sports Medicine, UKK Institute for Health Promotion Research, Tampere, Finland;

Department of Sports Sciences, Oslo Sports Trauma Research Center, Norwegian School of Sports Sciences, Oslo, Norway;

NeuroMuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland; and

§Tampere University of Applied Sciences, Tampere, Finland.

Corresponding Author: Anu Räisänen, MHSc, Tampere Research Center of Sports Medicine, UKK Institute for Health Promotion Research, PO BOX 30, 33501 Tampere, Finland (

Supported by the Finnish Ministry of Education and Culture, and the Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital (Grant 9N053). The funding sources did not have any involvement with the progress of the study.

The authors report no conflicts of interest.

Received January 21, 2015

Accepted October 20, 2015

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