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. 2023 May;35(5):312-319.
doi: 10.1589/jpts.35.312. Epub 2023 May 1.

The sitting active and prone passive lag test: a validity study in a symptomatic knee population

Sebastian Deepak  1   2 , George Priti  1 ; DScPT; Tsang Zishu  1 , Patel Chetan  3
Affiliations

The sitting active and prone passive lag test: a validity study in a symptomatic knee population

Sebastian Deepak et al. J Phys Ther Sci. 2023 May.

Abstract

[Purpose] This study aimed to determine the diagnostic utility of the sitting active and prone passive lag test in identifying terminal extension lag in unilaterally symptomatic knees. The lack of full extension at the knee leads to greater force of quadriceps activation, overloading of the weight bearing joints, abnormal gait mechanics, resulting in pain and dysfunction. [Participants and Methods] Participants were randomly assigned and evaluated by two blinded examiners, to determine the presence of extension lag at the knee. The reproducibility of test results between examiners was determined, for reliability. In addition, the ability of the test to identify the presence of extension lag in symptomatic knees and absence of extension lag in asymptomatic knees was assessed, for validity. [Results] The results revealed the test to possess an 'almost perfect' inter-rater reliability, high sensitivity, and moderate specificity. [Conclusion] The sitting active and prone passive lag test may be incorporated as a reliable and valid test to determine the presence of terminal knee extension lag in a unilaterally symptomatic knee population.

Keywords: Active lag; Diagnostic utility; Passive lag.

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Conflict of interest statement

No funding was obtained by the researchers for this study and the authors of this study do not report any conflict of interest.

Figures

Fig. 1.
Fig. 1.
Test position for ‘active lag’ showing positive active lag on the right.
Fig. 2.
Fig. 2.
Test position for ‘passive lag’ showing positive passive lag on the right.
Fig. 3.
Fig. 3.
Nomogram for likelihood ratio.
Fig. 4.
Fig. 4.
Receiver operating characteristic (ROC) analysis.
See this image and copyright information in PMC

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