THE LEVITATION TRI-COMPARTMENT UNLOADER: A NEW CONSERVATIVE CARE OPTION FOR HEALTHCARE PROFESSIONALS.
Many patients with knee osteoarthritis (OA) and other joint injuries experience increased pain during activities where the knee is bent and bearing weight, such as climbing or descending stairs, rising from a seated position, walking uphill, or squatting. During these activities, the compressive forces in the knee can increase up to sevenfold (1,2). The Levitation®2 Tri-Compartment Unloader is a unique solution for these patients and is the first knee brace capable of simultaneously unloading both the tibiofemoral and patellofemoral joints of the knee during weight-bearing flexion (3-7). By absorbing body weight into a patented spring-loaded hinge during weight-bearing knee flexion, Levitation can reduce the total load placed on the knee joint by over 50% (3,4,7), resulting in reduced pain and improved function (6,8). This is important because reducing joint loads to alleviate pain and improve function is widely considered to be best practice in the conservative treatment of knee OA (9,10). However, many patients find traditional unloading techniques such as weight loss and activity modification difficult to achieve or implement (11,12). Levitation’s unique spring-loaded hinge provides adjustable extension assistance (or “knee extension assist”) that is often used by healthcare providers to augment patient mobility and assist patients with neuromuscular retraining exercises (13).
- Patellofemoral knee OA
- Multi-compartment knee OA
- Cartilage defects
- Meniscus injuries
- Anterior knee pain
- Knee extensor deficiencies
- Combined tibiofemoral and patellofemoral unloading (3,4,7)
- Reduced pain and improved function during activities of daily living (6,8)
- Customizable knee extension assist (3-7)
- Promotes increased activity (8) and muscle strengthening (13-14)
How it's Different
Key differences between the Levitation Tri-Compartment Unloader and traditional knee braces Include –
- Levitation can unload both the patellofemoral and tibiofemoral joints of the knee simultaneously. Traditional OA braces are designed to offload one tibiofemoral compartment at a time (3,4,7).
- Unlike traditional knee OA braces, Levitation’s knee extension assist provides pain relief and joint unloading during knee flexion (3,4,6-8). This is particularly useful for patients with patellofemoral defects or OA.
- Levitation directly assists quadriceps strength and mobility (4-6), allowing for neuromuscular retraining (14).
How It Works
The quadriceps are a primary contributor to patellofemoral and tibiofemoral joint contact forces when the knee is in weight-bearing flexion (1,2). In fact, knee joint forces typically increase with knee flexion, reaching over 7x bodyweight in a squat (Table 1). This is because the quadriceps are required to exert large tensile forces on the knee joint in order to keep an upright posture when an individual’s center of gravity is displaced away from the joint’s midline (e.g., when crouching or squatting).
Table 1: Patellofemoral joint contact forces experienced during different activities of daily living.
Levitation functions by assisting the knee extension moment normally generated by the quadriceps when the knee is in flexion. By assisting the quadriceps, the large tensile forces normally transmitted to the patellofemoral and tibiofemoral joints via the quadriceps and patellar tendons respectively are reduced (3,4).
Assisting the quadriceps results in a rapid reduction of patellofemoral and tibiofemoral joint contact forces, which can be used to help prevent further joint damage (15) and which can rapidly reduce pain and improve function (8). Most importantly, the reduction in pain allows patients to begin exercising and retraining healthy movement patterns (8,14). As the patient regains their natural strength and stability, the assistance provided by the brace can be dialed back or turned off altogether.
Patient Explainer Video
The explainer video below is a useful resource to introduce and describe the function of the Levitation knee brace to your patients.
Brace Efficacy and Clinical Practice
Introducing the Levitation Tri-Compartment Unloader into Clinical Practice
Webinar by Dr. Ivan Wong, MD, and Dr. Emily Bishop, PhD.
This webinar was presented to physicians across Canada in May 2020 and focuses on:
- Patient report and radiographic diagnostic techniques for patients with knee pain
- Novel techniques for managing:
- Anterior knee pain and patellofemoral OA
- Multi-compartment knee OA
- Extensor mechanism defects
- Introduction of the Levitation Tri-Compartment Unloader to clinical practice
- How the brace works
- Case examples of the brace in clinical practice
- Overview of research completed to date
Summary of Key Studies
To validate the biomechanical and clinical benefits of Levitation, several research studies have been completed and several new studies are currently ongoing. These studies illustrate and support the differentiation and clinical benefits of Levitation. The following summary of research completed to date is non-exhaustive and is intended as a general overview. Please request the supporting full-text studies for additional details.
Preliminary evaluation of a new orthotic for patellofemoral and multi-compartment knee osteoarthritis (8)
Submitted to the Journal of Orthotics and Prosthetics.
An exploratory study of brace effectiveness was completed in a group of adults (n=40) with varied patterns of activity-related knee pain characteristic of patellofemoral, tibiofemoral, or multi-compartment knee OA. Participants used the Levitation brace for at least 1 month and reported on outcomes including pain, function, physical activity, and use of medications and other treatments before and after brace use. Validated outcome measures including the visual analog scale (VAS) and the Lower Extremity Functional Scale (LEFS) were used to assess pain and physical function (primary outcome measures) respectively. Exploratory measures were used to quantify physical activity levels and use of medication and other treatments (secondary outcome measures). The results demonstrated that:
- 95% of users with knee OA experienced a reduction in pain. Total pain (VAS) scores decreased significantly by over 36 mm. The improvement in pain scores exceeded the “PASS” threshold (16); that is, the pain score below which patients typically consider themselves well.
- A significant improvement of 16 points was observed on the Lower Extremity Function Scale (LEFS). The minimum clinically relevant change on the LEFS is 9 points (18).
- Overall, 70% of participants indicated increased weekly physical activity and 60% reported a decrease in their use of at least one other treatment.
- The study is currently under review.
Figure 1: The improvement in pain scores exceeded the externally validated “PASS” threshold (16); that is, the pain score below which patients typically consider themselves well.
Biomechanical Studies Examining the Unloading Effect of the Levitation knee brace
Several studies (3-7) have been completed examining the unloading effect of Levitation using standard and well established biomechanical techniques.
Design Evaluation of a Novel Multicompartment Unloader Knee Brace (3)
Published in the Journal of Biomechanical Engineering
The first biomechanical study by Budarick et al (3) outlines the unique design and function of the Levitation knee brace and demonstrates that Levitation can reduce patellofemoral and tibiofemoral joint contact forces to a level that would be achieved by losing 45 lbs of body weight1. By comparison, the OA Rehabilitator (the only other published and commercially available knee extension assist brace) reduces internal joint contact forces to a level that would be achieved by losing 5 lbs of body weight (Figure 2). The reported reduction of knee joint forces was at a static 90-degree knee bend.
Figure 2: (A) Assistive moment provided by the Levitation Tri-Compartment Unloader versus the OA Rehabilitator at varying brace flexion angles . Lines of best fit (R2 = 1) are presented for each brace profile. (B) Effective bodyweight reduction at 90 degrees of knee flexion offered by the Levitation Tri-Compartment Unloader and the OA Rehabilitator.
The Importance of Joint Unloading and the Effect of Weight Loss
The reduction of joint contact forces to a level that would be achieved by losing 45 pounds of body weight 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 OA agree that weight loss is an important intervention that improves both pain and function in patients with knee OA. However, for weight loss to be effective, research has shown that patients must lose at least 10% of their starting body weight, while the largest benefits are seen in patients who achieve a >20% reduction in body weight (17). For an average individual with knee OA weighing 205 pounds, a 20% bodyweight reduction (equivalent to losing 41 pounds) can be a daunting challenge. By reducing joint forces to a level that would be achieved by losing 45 pounds of body weight, unlike any other commercially available knee brace, Levitation can provide immediate joint unloading during knee flexion (i.e., when joint forces are highest). This in turn provides patients with rapid improvements in pain and function, thereby allowing patients to resume or increase their physical activity (6,8).
1For an average knee OA patient weighing 200 lbs, Levitation reduces joint loading to a level that would be achieved by losing 45 lb of body weight, a 22.5% reduction (3). Previous research shows that weight loss of at least 20% is required for the best clinical outcomes in patients with knee OA17.
Biomechanical Study of a Tri-Compartmental Unloader Brace for Patellofemoral or Multi-compartment Knee Osteoarthritis (4)
Submitted to the Journal of Biomechanical Engineering
This study replicated and extended the findings of Budarick et al (3) by examining patellofemoral and tibiofemoral joint contact forces, patellar and quadriceps tendon forces, as well as forces in the anterior and posterior cruciate ligaments across the range of motion for a deep knee bend (DKB). Forces were computed from 0 to 100 degrees of flexion. Different configurations of the brace were tested and compared to the joint forces observed when no brace was used.
The study demonstrated that Levitation significantly reduces joint contact forces, as well as patellar tendon, quadriceps tendon, and posterior cruciate ligament forces during weight-bearing activity from 30 to 100 degrees of flexion. Knee joint loads were reduced by between 30-50% (Figure 3).
Figure 3: Reduction of tibiofemoral, patellofemoral and quadriceps tendon forces during a deep knee bend test. The blue line represents joint forces observed without Levitation, while the green line represents joint forces observed with Levitation. The shaded regions are areas of statistical uncertainty.
Biomechanical Evaluation of a Tri-Compartment Unloader Knee Brace During Chair Rise and Lower and Stair Ambulation in Individuals with Knee Osteoarthritis
Research is underway at the University of Calgary to understand the biomechanical effect of The Levitation Tri-compartment Unloader (TCU) knee brace on patients with knee OA. This study has been approved by the Conjoint Health Research Ethics Board at the University of Calgary. Adult patients between the ages of 45 and 75 with moderate to severe multi-compartmental knee OA diagnosed by an orthopaedic surgeon are being recruited to participate in the study. Following informed consent, participants are fitted with a TCU knee brace and asked to perform several activities of daily living while wearing the brace and while unbraced. Three-dimensional movement data and muscle activity data are collected from a state-of-the-art motion capture system (Figure 4). Participants are asked to report on their level of pain experienced while performing the movements without the brace and while wearing the brace. To date, data has been collected on 9 patients at the Clinical Movement Assessment Lab at the McCaig Institute for Bone and Joint Health.
Figure 4: A study participant wearing the Levitation brace while climbing stairs during biomechanical data collection at the Clinical Movement Assessment Lab.
Preliminary data analysis shows that wearing the Levitation brace lowers quadriceps muscle effort and internal knee extension moments during a chair rise and lower movement as well as stair descent (Figure 5). While more data is required to confirm these trends, these findings are important because both of these measures have been shown to contribute to patellofemoral and tibiofemoral joint loading. Furthermore, this study is the first to capture the effect of wearing the Levitation brace on quadriceps muscle activity in knee OA patients, and provides evidence supporting the proposed mechanism of unloading the knee joint. Participants reported lower levels of pain while wearing the Levitation brace, suggesting that there is an immediate effect of the Levitation brace on knee pain during these weight-bearing knee flexion activities in patients with multi-compartmental knee OA.
Figure 5: Knee extension moment (%BWxH) during a chair rise and lower movement for a single study participant. Data is shown for the movement performed without the brace (blue), with the brace worn in low power (green), and with the brace worn in high power (red).
Accepted to the OARSI 2020 World Congress and Published in Osteoarthritis and Cartilage
Accepted to the 2020 Orthotics and Prosthetics Canada National Conference
Testing by the Canadian Military
During physical testing in healthy individuals conducted by the Canadian Military, Levitation significantly increased physical stamina and endurance (19). The following improvements were observed:
- A 10% improvement in the maximum number of loaded squats
- A 26% improvement in the maximum number of loaded leg presses
- No change in heart rate when walking with versus without the TCU.
Figure 6: (A) Group performance averages for maximal leg press and 45kg squat test with and without the Levitation orthosis. (B) Test performance from a single participant with meniscal injury.
Improvements were even more pronounced in an individual with a meniscus injury where seven- and ten-fold improvements were observed in the maximum number of squats and leg presses respectively. A summary of these findings has been published as a white paper by Spring Loaded (19) and is available for download on this page. Access to the original report is protected by the military.
Spring Loaded collaborates with researchers at Dalhousie University, the University of New Brunswick, the University of Calgary, the University of Guelph, the Queen Elizabeth II Foundation, and the Canadian Military. These research partners have provided insight on our design process and are conducting independent testing and validation of our knee brace products in a variety of different circumstances. Additional details about our ongoing research be found here.
- van Rossom, S., Smith, C.R., Thelen, D.G., Vanwanseele, B, Van Assche, D, Jonkers, I., 2018. Knee Joint Loading in Healthy Adults During Functional Excercises: Implications for Rehabilitation Guidelines. JOSPT 48(3), 162-173.
- Noyes, F. 2016. Noyes Knee Disorders: Surgery, Rehabilitation, Clinical Outcomes. Second Edition. Elsevier Health Sciences.
- Budarick, A.R., MacKeil, B.E., Fitzgerald, S., Cowper-Smith, C.D., 2020. Design Evaluation of a Novel Multicompartment Unloader Knee Brace. J. Biomech. Eng. 142.
- McGibbon, C.A., Brandon, S.C., Bishop, E.L., Cowper-Smith, C., Biden, E.N. 2020. Biomechanical study of a novel tri-compartmental unloader brace for the knee. Submitted to the Journal of Biomechanical Engineering.
- Bishop, E.L. Kuntze, G., Ronsky, J.L. Effect of a Tri Compartment Unloader Knee Brace on Knee Moments and Quadriceps Activity During a Chair Rise and Lower and Stair Descent in Individuals with Knee Osteoarthritis. Osteoarthritis and Cartilage 28 (2020) S243-244.
- Bishop, E.L. Kuntze, G., Sanni, S., Clark, M.L., Cowper-Smith, C.D., Ronsky, J.L. Effect of a Tri-Compartment Unloader Knee Brace on Knee Moments, Muscle Activity, Pain and Difficulty During Chair Rise and Lower in Individuals with Knee Osteoarthritis. Orthotics and Prosthetics Canada National Conference, Fredericton, Canada, August 2020.
- McGibbon, C.A., Mohamed, A. Knee Load Reduction from an Energy Storing Mechanical Brace: A Simulation Study. Canadian Society of Biomechanics, Halifax, Canada, August 2018.
- Budarick, A.R., Bishop, E.L., Clark, M.L., Cowper-Smith, C.D. Preliminary Evaluation of a new orthotic for patellofemoral and multi-compartment knee osteoarthritis. Submitted to JPO.
- McAlindon, T.E. Bannuru, R.R. et al., OARSI guidelines for the non-surgical management of knee osteoarthritis. Osteoarthritis and Cartilage 22 (2014) 363-388.
- Treatment of Osteoarthritis of the Knee Evidence Based Guideline, 2nd Edition. American Academy of Orthopaedic Surgeons (2013)
- Ekram, A.R.M.S., Crammond, B.R., Cicuttini, F.M, Urqhart, D.M., Teichtahl, A.J., Lombard, C.B., Liew, S.M., Wluka A.E., Weight Satisfaction, Management Strategies, and Health Beliefs in Knee Osteoarthritis Patients Attending an Outpatient Clinic. Intern. Med. J. (2016) 46(4), 435-442.
- Carmona-Terés, V., Moix-Queraltó, J., Pujol-Ribera, E., Lumillo-Gutiérrez, I., Mas, X., Batlle-Gualda, E., Gobbo-Montoya, M., Jodar-Fernández, L., and Berenguera, A., Understanding Knee Osteoarthritis from the Patients’ Perspective: A Qualitative Study, (2017), BMC Musculoskelet. Disord., 18(1), pp. 1–12.
- Doucet, R., Laroche, N. Osteoarthritis Physiotherapy Protocol. 2018. Independently prepared for Spring Loaded Technology.
- Cherian, J.J., Bhave, A., Kapadia, B.H., Starr, R., McElroy, M.J., Mont, M.A., 2015. Strength and Functional Improvement Using Pneumatic Brace with Extension Assist for End-Stage Knee Osteoarthritis: A Prospective, Randomized Trial. J Arthroplasty 30 747-753.
- Waller, C., Hayes, D., Block, J. E., and London, N. J., Unload It: The Key to the Treatment of Knee Osteoarthritis (2011) Knee Surg. Sports Traumatol. Arthrosc., 19(11), pp. 1823–9.
- Tubach F, Ravaud P, Baron G, Falissard B, Logeart I, Bellamy N, et al. Evaluation of clinically relevant states in patient reported outcomes in knee and hip osteoarthritis: The patient acceptable symptom state. Ann Rheum Dis. 2005;64(1):34–7
- Messier, S. P., Resnik, A. E., Beavers, D. P., Mihalko, S. L., Miller, G. D., Nicklas, B. J., 418 DeVita, P., Hunter, D. J., Lyles, M. F., Eckstein, F., Guermazi, A., and Loeser, R. F., 419 2018, “Intentional Weight Loss in Overweight and Obese Patients With Knee 420 Osteoarthritis: Is More Better?,” Arthritis Care Res., 70(11), pp. 1569–1575.
- Binkley JM, Stratford PW, Lott SA, Riddle DL. The Lower Extremity Functional Scale (LEFS): Scale Development, Measurement Properties, and Clinical Application. Phys Ther. 1999;79(4):371–83.
- Spring Loaded Technology. Summary of Physical Performance Improvements Observed in Military Personnel While Wearing the Levitation Knee Orthosis. (2018).
All the resources are available in the downloadable pdf format. Click the button below to view & download resources.
Effect of a tri compartment unloader knee brace on knee moments and quadriceps activity during a chair rise and lower and stair descent in individuals with knee osteoarthritis
Published in Osteoarthritis and Cartilage.
Effect of a Tri-Compartment Unloader Knee Brace on Knee Moments, Muscle Activity, Pain and Difficulty During Chair Rise and Lower in Individuals with Knee Osteoarthritis
Design Evaluation of a Novel Multicompartment Unloader Knee Brace
Published in the Journal of Biomechanical Engineering
How it Works