Commentary: A Patient-Specific Lower Extremity Biomechanical Analysis of a Knee Orthotic during a Deep Squat Movement

Christine Dailey Walck

Department of Mechanical Engineering, Embry-Riddle Aeronautical University, Daytona Beach, Florida, USA


The recent study by Walck et al., titled "A Patient-Specific Lower Extremity Biomechanical Analysis of a Knee Orthotic during a Deep Squat Movement," provides a novel insight into the biomechanical impacts of knee orthotics, particularly the non-linear spring-loaded (NLSL) knee joint orthosis (KJO)1. This commentary aims to delve into the implications, interpretations, and evaluations of the findings, contextualizing them within the broader discourse on knee orthotics.

Critical Analysis of the Study

The study showcases a sophisticated approach to understanding the biomechanical nuances of knee braces, a topic that has become increasingly relevant given the influx of knee brace usage in both rehabilitative and athletic settings. The research's primary conclusion—that the NLSL KJO shifts biomechanical strategies from quadriceps-dominant to posterior chain muscle engagement—is both significant and controversial.

The methodology employed in the study, focusing solely on a single healthy male participant, presents both strengths and limitations. While it allows for a detailed, patient-specific analysis, it raises concerns regarding the generalizability of the findings. Moreover, the study utilizes the common open-source musculoskeletal model by OpenSim, which assumes static environments, unchanging conditions, and a perpetual state of health. However, patients typically wear braces when they are experiencing health issues or during rehabilitation, indicating that their conditions are dynamic and evolving.

Additionally, it is crucial to consider the broader implications of changing biomechanical strategies through the use of braces. For instance, altering muscle activation patterns, such as engaging the posterior chain muscles, can enhance stability and control of knee motion while alleviating stress on the quadriceps. This shift in biomechanical strategies may lead to improved control during knee extension and flexion, resulting in greater overall stability.

Furthermore, orthosis usage has the potential to promote activation and strengthening of the muscles in the posterior chain, including the gluteal muscles, posterior thigh muscles, and sura muscles. This can contribute to enhanced muscular balance and more uniform force distribution during movement, potentially translating into improved sports performance.

However, it's essential to acknowledge the potential side effects associated with using a nonlinear spring-loaded orthosis. These may include discomfort, pain, and an extended period of adaptation and transition. Therefore, while the study provides valuable insights, there is a pressing need for expanded research involving a more diverse demographic to validate these findings universally and address the dynamic nature of orthotic usage in real-world scenarios.

Contextualizing Within the Current Debate

The debate surrounding knee braces is multifaceted. On one hand, many practitioners and patients advocate for their use, citing support, stability, and injury prevention2,3. On the other, critics argue that knee braces can hinder recovery by creating dependency and weakening the natural muscle support system4. While others advocate that they have no effect at all5,6. The study by Walck et al. enters this debate with a fresh perspective, suggesting that knee orthotics, specifically the NLSL KJO, can actively alter muscle activation and movement patterns, potentially countering the argument that braces inhibit natural muscle function.

Implications and Broader Context

The implications of Walck et al.'s study extend beyond the specific context of the NLSL KJO. It challenges the traditional view of knee braces as purely passive support mechanisms, suggesting a potential paradigm shift towards seeing them as active modifiers of biomechanics. This perspective could revolutionize how we approach the design and application of orthotics, emphasizing their role in rehabilitation and injury prevention.

However, the study’s focus on a single, healthy male subject raises concerns about its applicability to a broader population. Knee orthotics are used by a diverse group of individuals, including athletes, the elderly, and patients with various musculoskeletal conditions. The biomechanical responses to knee orthotics can vary significantly based on factors like age, gender, body weight, and the specific nature of the injury or condition7. Therefore, while the study provides valuable insights, its findings need to be tested on a more diverse participant pool to ascertain their universal applicability.

Controversies and Key Omissions

One of the controversies in the field of knee orthotics is the perception of their effectiveness. There is a widespread belief that knee braces may not provide significant benefits or, worse, may impede natural recovery processes. Walck et al.'s study counters this by demonstrating the active biomechanical role that a knee orthosis can play. However, the study may have benefited from a comparative analysis with other types of knee braces, which would have provided a more comprehensive understanding of the NLSL KJO's unique features and benefits.

Another key omission in the study is the lack of long-term follow-up data. Understanding how the NLSL KJO affects muscle function and joint mechanics over time is crucial, especially in the context of rehabilitation and chronic injury management.

Supporting Arguments for a Stronger Presentation

To strengthen their presentation, the authors could have included a more detailed discussion on the potential implications of their findings for different types of knee injuries and conditions. Additionally, incorporating patient-reported outcomes, such as pain relief and improvement in function, would have provided a more holistic view of the brace's effectiveness.


The study by Walck et al. is a significant contribution to the field of biomechanics and orthotics. It opens up new avenues for the design and use of knee braces as active tools in rehabilitation and injury prevention. However, further research involving a wider range of participants and long-term follow-up studies is essential to fully understand the implications of these findings. This study sets the stage for ongoing discussions and explorations in the realm of knee orthotics, encouraging a more nuanced and evidence-based approach in their application.

Encouraging Active Discussion

This commentary aims to spark active discussion among practitioners, researchers, and patients on the role and effectiveness of knee orthotics. As the field evolves, it is crucial to continue questioning, analyzing, and debating the best practices in orthopedic care, ensuring that interventions are grounded in robust evidence and tailored to the diverse needs of patients.


  1. Christine W, Victor H, Daryl O, et al. A patient-specific lower extremity biomechanical analysis of a knee orthotic during a deep squat movement. Med Eng Phys. 2020; 80: 1-7.
  2. Baltaci G, Aktas G, Camci E, et al. The effect of prophylactic knee bracing on performance: balance, proprioception, coordination, and muscular power. Knee Surg Sports Traumatol Arthrosc. 2011; 19(10): 1722-8.
  3. Najibi S, Albright JP. The use of knee braces, part 1: Prophylactic knee braces in contact sports. Am J Sports Med. 2005; 33(4): 602-11.
  4. Wu GK, Ng GY, Mak AF. Effects of knee bracing on the functional performance of patients with anterior cruciate ligament reconstruction. Arch Phys Med Rehabil. 2001; 82(2): 282-5.
  5. Möller E, Forssblad M, Hansson L, et al. Bracing versus nonbracing in rehabilitation after anterior cruciate ligament reconstruction: a randomized prospective study with 2-year follow-up. Knee Surg Sports Traumatol Arthrosc. 2001; 9(2): 102-8.
  6. McDevitt ER, Taylor DC, Miller MD, et al. Functional bracing after anterior cruciate ligament reconstruction: a prospective, randomized, multicenter study. Am J Sports Med. 2004; 32(8): 1887-92.
  7. Georgiev T, Angelov AK. Modifiable risk factors in knee osteoarthritis: treatment implications. Rheumatol Int. 2019; 39(7): 1145-1157.

Article Info

Article Notes

  • Published on: February 21, 2024


  • Deep Squat Movement
  • Lower Extremity Biomechanical Analysis
  • Knee Orthotic
  • knee joint orthosis (KJO)
  • non-linear spring-loaded (NLSL)


Dr. Christine Dailey Walck,
Department of Mechanical Engineering, Embry-Riddle Aeronautical University, Daytona Beach, Florida, USA;

Copyright: ©2024 Walck CD. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License.