Design Innovation Paper

New Adjustable Unloader Knee Brace and Its Effectiveness

[+] Author and Article Information
Gajendra Hangalur, Ryan Bakker, Naveen Chandrashekar

Mechanical and Mechatronics Engineering,
University of Waterloo,
Waterloo, ON N2 L 3G1, Canada
e-mail: nchandra@uwaterloo.ca

Sebastian Tomescu

Sunnybrook Health Sciences Centre,
University of Toronto,
43 Wellesley Street East,
Toronto, ON M4Y 1H1, Canada

Manuscript received November 8, 2016; final manuscript received October 16, 2017; published online November 22, 2017. Assoc. Editor: Elizabeth Hsiao-Wecksler.

J. Med. Devices 12(1), 015001 (Nov 22, 2017) (5 pages) Paper No: MED-16-1357; doi: 10.1115/1.4038439 History: Received November 08, 2016; Revised October 16, 2017

Unloader knee braces are prescribed for patients with unicompartmental osteoarthritis of the knee. These braces aim to reduce pain in patients by applying a coronal moment to the knee to unload the symptomatic knee compartment. However, existing unloading mechanisms use straps that go directly behind the knee joint, to apply the needed moment. This can impinge on the popliteal artery and peroneal nerves thereby causing discomfort to the patient. Hence, these braces cannot be worn for prolonged periods of time. This research focused on developing a new knee brace to improve comfort while unloading the osteoarthritic knee. A new knee brace was developed that uses a four-point bending approach to unload the knee. In this brace, unloading can be adjusted, and the unloading mechanism is away from the joint. The new brace was tested on a cadaver specimen to quantify its capability to unload the knee compartment. The brace was also worn by a patient with osteoarthritis who subjectively compared it to his existing unloader brace. During cadaver testing, the new brace design could reduce the force exerted on the medial condyle by 25%. Radiographic images of the patient's knee confirmed that the brace unloaded the medial condyle successfully. The patient reported that the new brace reduced pain, was significantly comfortable to wear and could be used for a longer duration in comparison to his existing brace.

Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.


Felson, D. T. , Lawrence, R. C. , Dieppe, P. A. , Hirsch, R. , Helmick, C. G. , Jordan, J. M. , Kington, R. S. , Lane, N. E. , Nevitt, M. C. , Zhang, Y. , Sowers, M. , McAlindon, T. , Spector, T. D. , Poole, A. R. , Yanovski, S. Z. , Ateshian, G. , Sharma, L. , Buckwalter, J. A. , Brandt, K. D. , and Fries, J. F. , 2000, “ Osteoarthritis: New Insights. Part 1: The Disease and Its Risk Factors,” Ann. Intern. Med., 133(8), pp. 635–646. [CrossRef] [PubMed]
Shelburne, K. B. , Torry, M. R. , and Pandy, M. G. , 2005, “ Muscle, Ligament, and Joint-Contact Forces at the Knee During Walking,” Med. Sci. Sports Exercise, 37(11), pp. 1948–1956. [CrossRef]
Kutzner, I. , Kuther, S. , Heinlein, B. , Dymke, J. , Bender, A. , Halder, A. , and Bergmann, G. , 2011, “ The Effect of Valgus Braces on Medial Compartment Load of the Knee Joint—In Vivo Load Measurements in Three Subjects,” J. Biomech., 44(7), pp. 1354–1360. [CrossRef] [PubMed]
Pollo, F. E. , Otis, J. C. , Backus, S. I. , Warren, R. F. , and Wickiewicz, T. L. , 2002, “ Reduction of Medial Compartment Loads With Valgus Bracing of the Osteoarthritic Knee,” Am. J. Sports Med., 30(3), pp. 414–421. [CrossRef] [PubMed]
Dennis, D. A. , Komistek, R. D. , Nadaud, M. C. , and Mahfouz, M. , 2006, “ Evaluation of Off-Loading Braces for Treatment of Unicompartmental Knee Arthrosis,” J. Arthroplasty, 21(4), pp. 2–8. [CrossRef] [PubMed]
Finger, S. , and Paulos, L. E. , 2002, “ Clinical and Biomechanical Evaluation of the Unloading Brace,” J. Knee Surg., 15(3), pp. 155–159. [PubMed]
Edwards, P. H. , Wright, M. L. , and Hartman, J. F. , 2005, “ A Practical Approach for the Differential Diagnosis of Chronic Leg Pain in the Athlete,” Am. J. Sports Med., 33(8), pp. 1241–1249. [CrossRef] [PubMed]
Englund, J. , 2005, “ Chronic Compartment Syndrome: Tips on Recognizing and Treating,” J. Fam. Pract., 54(11), pp. 955–960. [PubMed]
McCrory, P. , Bell, S. , and Bradshaw, C. , 2002, “ Nerve Entrapments of the Lower Leg, Ankle and Foot in Sport,” Sport Med., 32(6), pp. 371–391. [CrossRef]
Squyer, E. , Stamper, D. L. , Hamilton, D. T. , Sabin, J. A. , and Leopold, S. S. , 2013, “ Unloader Knee Braces for Osteoarthritis: Do Patients Actually Wear Them?,” Clin. Orthop. Relat. Res., 471(6), pp. 1982–1991. [CrossRef] [PubMed]
Draganich, L. , Reider, B. , Rimington, T. , Piotrowski, G. , Mallik, K. , and Nasson, S. , 2006, “ The Effectiveness of Self-Adjustable Custom and Off-the-Shelf Bracing in the Treatment of Varus Gonarthrosis,” J. Bone Jt. Surg. Am., 88(12), pp. 2645–2652.
Hangalur, G. , Brenneman, E. , Nicholls, M. , Bakker, R. , Laing, A. , and Chandrashekar, N. , 2016, “ Can a Knee Brace Reduce the Strain in the Anterior Cruciate Ligament? A Study Using Combined In Vivo/In Vivo Method,” Prosthet. Orthot. Int., 40(3), pp. 349–399. [CrossRef]
Cassidy, K. , Hangalur, G. , Sabharwal, P. , and Chadrashekar, N. , 2013, “ Combined In Vivo/In Vivo Method to Study Anteriomedial Bundle Strain in the Anterior Cruciate Ligament Using a Dynamic Knee Simulator,” ASME J. Biomech. Eng., 135(3), p. 035001. [CrossRef]
Ramsey, D. K. , Briem, K. , and Axe, M. J. , 2007, “ A Mechanical Hypothesis for the Effectiveness of Knee Bracing for Medial Compartment Knee Osteoarthritis,” J. Bone Jt. Surg. Am., 89(11), pp. 2398–2407.
Birmingham, T. B. , Bryant, D. M. , Giffin, J. R. , Litchfield, R. B. , Kramer, J. F. , Donner, A. , and Fowler, P. J. , 2008, “ A Randomized Controlled Trial Comparing the Effectiveness of Functional Knee Brace and Neoprene Sleeve Use After Anterior Cruciate Ligament Reconstruction,” Am. J. Sports Med., 36(4), pp. 648–655. [CrossRef] [PubMed]


Grahic Jump Location
Fig. 6

Cyclic testing machine: (1) brace linkage, (2) and (3) slider crank mechanism, and (4) tester frame

Grahic Jump Location
Fig. 5

(a) Frontal, (b) sagittal, and (c) backside view of the newly designed brace. The arrows in (a) show the direction of the forces applied by the rigid case on the leg. “S” are the straps.

Grahic Jump Location
Fig. 4

Unloader mechanism: (a) straight position and (b) unloaded position

Grahic Jump Location
Fig. 3

Additional views of the assembly: (a) medial, (b) sagittal, and (c) lateral views. All dimensions are in millimeter.

Grahic Jump Location
Fig. 2

New adjustable knee brace upright link. Assembly components: (1) thermoplastic case, (2) outer upright, (3) spring plate, (4) floating hinge, (5) lever arm, (6) set screw, (7) inner upright, and (8) polycentric joint

Grahic Jump Location
Fig. 7

Tekscan pressure distribution plot of cadaver knee with 580 N compressive load: (a) without brace, indicating 480 N force in the medial condyle and (b) with brace, showing 360 N through the medial condyle. P, posterior; L, lateral. Each sensel is 1.29 mm2.

Grahic Jump Location
Fig. 8

X-rays of unbraced (a) and braced (b) knee under nonweight bearing condition. The dark lines show the change in angle between the condylar surfaces.

Grahic Jump Location
Fig. 1

The new adjustable unloader brace. “U” are the uprights, P is the polycentric joint, and “T” are the thermoplastic cases for thigh and shank.



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In