Northwestern University Feinberg School of Medicine

Northwestern University Prosthetics-Orthotics Center

Lateral Stability and Recovery Strategies among Persons with Below Knee Amputation

Principal Investigators: Matthew J. Major, PhD; Keith Gordon, PhD

Research Engineers: Geoffery Brown, MS; Lilly Tran, MS; Mary Wu, MS (Northwestern University)

Student Investigators: Xinlin Chen, Franklyn Ndubuisi-Obi, Chelsi Serba (Northwestern University); SeanDwijendra (Rush University)

Funded by: NUCATS Voucher (Tier 1) Program

Status: In Progress

Background and Significance

Approximately half of community dwelling persons with lower-limb amputation fall every year [1]. Frontal-plane asymmetries observed during quiet standing [2-6] suggest that persons with below-knee amputation (BKA) have limited ability to respond to lateral perturbations during gait. Although sagittal plane stability has been investigated [4, 8-10], the mechanisms underlying successful recovery following a destabilizing lateral perturbation are poorly understood. Characterizing the mechanisms utilized by this pathological group to achieve locomotor stability will serve as a platform to inform therapeutic and prosthetic interventions to minimize the risk of falls and fall-related injury.

Testing balance and lateral stability on a perturbation treadmill.Aims and Hypothesis

The purpose of this pilot study is to quantify the response mechanisms persons with unilateral BKA employ to resist and recover from lateral perturbations during walking. Due to the loss of an active ankle joint and critical forms of proprioceptive feedback [4, 5, 10-12], we hypothesize that, compared to intact controls, persons with BKA will depend heavily on passive mechanisms of stabilization (e.g., wider steps, greater margins of stability, increased double support time) that deemphasize accurate sensation and response to perturbations.

Analysis Plan

To quantify the mechanisms used to control lateral stability, we will measure how 10 individuals with BKA who are classified as community ambulators compare with 10 age- and gender-matched control participants in their response to lateral force perturbations applied during treadmill walking using a motorized perturbation system (See Figure). 

Impact and Plans for Future Research

Given the novelty of the proposed research and limited knowledge on this topic, findings from this study will be of immediate clinical relevance by providing greater understanding of the mechanisms that persons with BKA adopt to maintain frontal-plane stability and to identify deficiencies in these strategies. By demonstrating their reliance on passive mechanisms of stability, we will emphasize the importance of designing effective balance training and ankle-foot prostheses with mechanical properties tuned to match individual stabilization strategies. These efforts will elevate amputee clinical care by helping to enhance the quality of evidence-based practice. Importantly, these results will provide strong rationale for future grant proposals that will investigate: 1) interactions between prosthesis mechanical properties and recovery strategies following perturbation to inform prosthesis optimization, and 2) effects of targeted therapeutic interventions on recovery strategies to address balance deficiencies in this pathological group.

Plan for Future Funding

This novel and relatively unexplored topic requires adequate pilot data to generate future funding through competitive grant proposals. NUCATS sponsorship is supporting our efforts to generate preliminary results directed toward securing future funding. We intend to use these preliminary data for grant proposals (NIH R01, VA Merit).


  1. Miller, W.C., M. Speechley, and B. Deathe, The prevalence and risk factors of falling and fear of falling among lower extremity amputees. Archives of Physical Medicine and Rehabilitation, 2001. 82(8): p. 1031-7.
  2. Nadollek, H., S. Brauer, and R. Isles, Outcomes after trans-tibial amputation: the relationship between quiet stance ability, strength of hip abductor muscles and gait. Physiotherapy Research International, 2002. 7(4): p. 203-14.
  3. Rougier, P.R. and J. Bergeau, Biomechanical analysis of postural control of persons with transtibial or transfemoral amputation. American Journal of Physical Medicine and Rehabilitation, 2009. 88(11): p. 896-903.
  4. Vrieling, A.H., et al., Balance control on a moving platform in unilateral lower limb amputees. Gait and Posture, 2008. 28(2): p. 222-8.
  5. Quai, T.M., S.G. Brauer, and J.C. Nitz, Somatosensation, circulation and stance balance in elderly dysvascular transtibial amputees. Clinical Rehabilitation, 2005. 19(6): p. 668-76.
  6. Isakov, E., et al., Standing sway and weight-bearing distribution in people with below-knee amputations. Archives of Physical Medicine and Rehabilitation, 1992. 73(2): p. 174-8.
  7. Qiao, M. and D.L. Jindrich, Compensations during unsteady locomotion. Integrative and Comparative Biology, 2014. 54(6): p. 1109-21.
  8. Curtze, C., et al., Balance recovery after an evoked forward fall in unilateral transtibial amputees. Gait and Posture, 2010. 32(3): p. 336-41.
  9. Nederhand, M.J., et al., Dynamic Balance Control (DBC) in lower leg amputee subjects; contribution of the regulatory activity of the prosthesis side. Clinical Biomechanics (Bristol, Avon), 2012. 27(1): p. 40-5.
  10. Vanicek, N., et al., Postural responses to dynamic perturbations in amputee fallers versus nonfallers: a comparative study with able-bodied subjects. Archives of Physical Medicine and Rehabilitation, 2009. 90(6): p. 1018-25.
  11. Buckley, J.G., D. O'Driscoll, and S.J. Bennett, Postural sway and active balance performance in highly active lower-limb amputees. American Journal of Physical Medicine and Rehabilitation, 2002. 81(1): p. 13-20.
  12. Hermodsson, Y., et al., Standing balance in trans-tibial amputees following vascular disease or trauma: a comparative study with healthy subjects. Prosthetics and Orthotics International, 1994. 18(3): p. 150-8.


Major, Matthew (2016) Locomotor Stability of Upper and Lower Limb Prosthesis Users. VA Research Day, Jesse Brown VAMC, May 20, Chicago, IL.

Volunteer as a Research Subject

Effects of Prosthetic Ankle Foot Stiffness on Lateral Stability of Below-Knee Prosthesis Users