Intelligent stretching of ankle joints with contracture/spasticity

Li Qun Zhang*, Sun G. Chung, Zhiqiang Bai, Dali Xu, Elton M.T. Van Rey, Mark W. Rogers, Marjorie E. Johnson, Elliot J. Roth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

118 Scopus citations


An intelligent stretching device was developed to treat the spastic/contractured ankle of neurologically impaired patients. The device stretched the ankle safely throughout the range of motion (ROM) to extreme dorsiflexion and plantarflexion until a specified peak resistance torque was reached with the stretching velocity controlled based on the resistance torque. The ankle was held at the extreme position for a period of time to let stress relaxation occur before it was rotated back to the other extreme position. Stretching was slow at the joint extreme positions, making it possible to reach a larger ROM safely and it was fast in the middle ROM so the majority of the treatment was spent in stretching the problematic extreme ROM. Furthermore, the device evaluated treatment outcome quantitatively in multiple aspects, including active and passive ROM, joint stiffness and viscous damping and reflex excitability. The stretching resulted in considerable changes in joint passive ROM, stiffness, viscous damping and reflex gain. The intelligent control and yet simple design of the device suggest that with appropriate simplification, the device can be made portable and low cost, making it available to patients and therapists for frequent use in clinics/home and allowing more effective treatment and long-term improvement.

Original languageEnglish (US)
Pages (from-to)149-157
Number of pages9
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number3
StatePublished - Sep 2002


  • Reflex
  • Spasticity
  • Stiffness
  • Stretch
  • Stroke

ASJC Scopus subject areas

  • Internal Medicine
  • Neuroscience(all)
  • Biomedical Engineering


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