First evaluation of a novel tri-compartment offloader

Research Summary

First evaluation of a novel tri-compartment offloader

Design evaluation of a novel multicompartment offloader knee brace

Budarick, A.R., MacKeil, B. E., Fitzgerald, S., and Cowper-Smith, C.D. (2020). Journal of Biomechanical Engineering. 142(1).

Key Findings

Reduced Knee Joint Forces

At a 90 degree flexion angle, PF and TF joint contact forces were reduced by an amount equivalent to losing 45 lb of bodyweight.

Powerful extension assistance

A Spring Loaded brace is found to provide sufficiently powerful extension assistance to offload all three knee compartments when the knee is flexed and bearing weight.

Confirmed by Subsequent Research

The offloading capabilities of Spring Loaded bracing, as indicated in this study, are replicated in future studies.

This study outlined the unique design of a novel tri-compartment offloader (TCO) knee brace and analyzed its potential to offload multiple compartments of the knee. The TCO’s force output was measured in order to calculate the capacity of the brace to offload the knee joint at various angles. The findings demonstrated that, at a 90-degree knee bend, the TCO can reduce patellofemoral (PF) and tibiofemoral (TF) joint contact forces to a level that would be achieved by losing 45 lb of bodyweight (Figure 2B). For comparison, the only other commercially available knee extension assist brace was tested and found to reduce internal joint contact forces to a level that would be achieved by losing 5 lb of bodyweight.


Figure 2A

Assistive moment provided by a Spring Loaded Tri-Compartment Offloader versus the OA Rehabilitator at varying brace flexion angles.


Assistive - knee extension assist - effect of Levitation knee brace
Offloader Knee Brace Bodyweight Reduction

Figure 2B

Effective bodyweight reduction at 90 degrees of knee flexion offered by a Spring Loaded Tri-Compartment Offloader and the OA Rehabilitator.

implications for care

The Importance of Joint Offloading and the Effect of Weight Loss

The reduction of joint contact forces to a level that would be achieved by losing 45 lb of bodyweight is important for understanding how Levitation can provide rapid pain relief and functional improvement for patients with knee OA.

Clinical guidelines for the conservative treatment of knee osteoarthritis (OA) agree that weight loss is an important intervention that can improve pain and function while simultaneously helping to delay the progression of knee OA. For weight loss to be effective in the treatment of OA, research has shown that patients must lose at least 10% of their starting bodyweight, while the largest benefits are seen in patients who achieve a >20% reduction in bodyweight. For an average individual with knee OA weighing 205 lb, a 20% body weight reduction can be a daunting challenge. The findings of this study indicated that a TCO can reduce joint forces to a level that would be achieved by losing 45 lb of bodyweight, which is the equivalent of a 22% bodyweight reduction in a 205 lb individual and a 27% bodyweight reduction in a 165 lb individual.2- Messier, S. P. et al. 2018. Arthritis Care Res. 70(11)

The data showed that the TCO reduced forces in both the PF and TF joints, indicating that a TCO’s spring loaded hinge is sufficiently powerful to provide clinically meaningful tri-compartment offloading benefits. Given that offloading the knee is commonly associated with a reduction in pain for patients with knee OA, the researchers concluded that the TCO may be an effective treatment option to reduce pain and functional limitations in patients with multicompartmental osteoarthritis (OA), allowing them to resume or increase their physical activity.3– Budarick, A.R. et al. 2020.  J. Biomech. Eng. 142.
– Bishop, E.L. et al. 2020. Osteoarthritis and Cartilage 28

This study was our first formal evaluation of the biomechanical effects of a Spring Loaded knee brace. It provided the first data supporting the tri-compartment offloading effect of the brace. These findings informed the direction of future research and have since been replicated in independent studies that focused on the biomechanical effects of Spring Loaded bracing.4– McGibbon, C.A. et al. 2020. Front. Bioeng. Biotech.
– Bishop, E.L. et al. 2020. Osteoarthritis and Cartilage 28

Partner Institutions

ACOA Atlantic Innovation Fund

A part of the Government of Canada’s commitment to increasing business productivity, growth and competitiveness, the AIF is helping Atlantic Canada compete at home and abroad by supporting the development of innovative products and services that lead to commercial success.