The Root-Ely Modified Test of Rectus Femoris Spasticity Has Reliability in Individuals with Cerebral Palsy



Stiff-knee gait is a common gait deviation in individuals with cerebral palsy (CP) due to rectus femoris (RF) muscle spasticity. The Duncan-Ely test is a velocity-dependent measurement of spasticity that is recorded as positive or negative. At our institution, we use a modification of the Duncan-Ely test, a 5-point ordinal rating scale, which delineates where the catch occurs within the rapid arc of knee flexion. It has been named the Root-Ely test.


We sought to determine the intra- and inter-rater reliability of the Duncan-Ely and Root-Ely tests in pediatric patients with CP.


A convenience sample of 20 ambulatory subjects was recruited; mean age was 10.5 ± 4.5 years, and the Gross Motor Function Classification System (GMFCS) levels were I–III. Five clinicians measured each individual’s RF spasticity using the Root-Ely protocol during a single visit. Simple κ statistics with 95% confidence intervals (CI) were utilized for intra-rater reliability and weighted κ statistics with 95% CI for inter-rater reliability.


The Root-Ely scale intra-rater reliability was 0.77 to 0.90 and inter-rater reliability was 0.32 to 0.87. Inter-rater reliability was good to excellent among experienced clinicians and fair to moderate in new clinicians.


The Root-Ely 5-point scale has acceptable intra- and inter-rater reliability in pediatric individuals with CP among experienced clinicians. The Root-Ely test allows experienced clinicians to reliably quantify severity of RF spasticity and may give orthopaedic surgeons a clinical tool to better predict ideal candidates for RF transfers in individuals with CP in order to improve stiff-knee gait.

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The authors acknowledge Leon Root, MD (1929–2015), for providing exceptional care to his patients and for generously sharing his time and knowledge with his colleagues. He was and continues to be an inspiration to all. Thank you to all patients and families who volunteered to participate in this study.

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Corresponding author

Correspondence to Lisa C. Drefus PT, DPT.

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Conflict of Interest

Lisa C. Drefus, PT, DPT, Siobhan Clarke, PT, DPT, Karen Resnik, PT, DPT, Jayme Koltsov, PhD, Emily R. Dodwell, MD, David M. Scher, MD declare that they have no conflicts of interest.

Human/Animal Rights

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2013.

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Informed consent was obtained from all patients for being included in this study.

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Level of Evidence: Diagnostic Study, Level III

Work performed at Hospital for Special Surgery

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Drefus, L.C., Clarke, S., Resnik, K. et al. The Root-Ely Modified Test of Rectus Femoris Spasticity Has Reliability in Individuals with Cerebral Palsy. HSS Jrnl 14, 143–147 (2018).

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  • Duncan-Ely test
  • Root-Ely test
  • rectus femoris spasticity
  • stiff-knee gait
  • cerebral palsy