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Aircast AirSport Ankle Brace

Donjoy Knee Brace Technology Explained

4 CommentsSaturday, 6 June 2009  |  Paul

Donjoy Knee Brace Technology Explained

Donjoy knee braces have a reputation as the ultimate knee supports, providing stability through the Donjoy 4-Points-Of Leverage-System, giving you confidence to ski and run, once again putting your knee through its paces.

Who Are Donjoy and What Makes Their Knee Supports and Braces So Special?

Donjoy are based in California in the USA, and are manufacturers of knee supports and braces such as the Donjoy Armor, Donjoy 4Titude, Donjoy Legend and Donjoy ACL Everyday. The technology Donjoy use to create their braces is constantly evolving to meet the diverse needs of modern sports and activities. The development of a Donjoy brace requires extensive strength, functional and cycle testing of all materials and components.

Donjoy use their Biomechanics Laboratory to develop their braces by using a robotic knee. This was vital in the development of the Donjoy 4-Points-Of-Leverage system. The robotic knee uses pneumatically actuated cables to simulate various states of the human knee providing a testing environment for the different loads and positions a knee may be subjected to. The robotic knee is able to simulate loads that vary from the swing phase of gait, where very little load is going through a joint, up to the massive compressive loads which are forced across a joint when coming of a jump. Donjoy can further manipulate the ACL cable to replicate common sports injuries. The use of the Biomechanics Lab and the robotic knee allow Donjoy to assess how much the tibia moves without a brace and then repeat the testing process with a Donjoy brace to perfect the reduction in tibial translation.

Donjoy 4-Point-Of-Leverage System

Through the 4-Points-of-Leverage™ rigid cuff and strap configuration, a posterior force is applied to the tibia preventing anterior movement.

The 4-Points-of-Leverage™ brace design:

  • Significantly reduces ACL strain*
  • Provides a constant dynamic load

Point of Leverage 1 (Point 1)

  • The tibia is anchored by a cuff placed at the bottom of the posterior calf.

Point of Leverage 2 (Point 2)

  • The femur is anchored by a cuff placed at the top of the anterior thigh.

Point of Leverage 3 (Point 3)

  • A strap across the back of the lower thigh pushes the femur anteriorly.

Point of Leverage 4 (Point 4)

  • A strap placed on the anterior tibia applies an active constant load to prevent anterior tibia translation.

*Fleming et all (2000), The influence of functional Knee Bracing on the ACL Strain Biomechanics in Weightbearing and Nonweightbearing Knees, The American Journal of Sports Medicine, Vol. , Nr. 6, p. 815-824

How Donjoy 4-Point Braces Protect The ACL Deficient Knee?

Patients with an ACL deficient knee are havingan anterolateral instability that causes “giving way” of the knee.

Trying to “de-rotate” and control instability of the ACL deficient knee in a direct way with a brace is very hard to do.

Therefore the DJO™ ligament braces try to stabilise the knee in an indirect way through the biomechanical 4-point design.

The 4-point system is clinically proven to be the most effective way to prevent anterior translation of the tibia.

By effectively reducing or preventing (*) anterior translation the 4-point brace in an indirect way avoids or reduces the anterolateral instability (endorotation) in ACL deficient knees and allows the patients to  regain knee stability.

Fourcepoint Hinge Technology

Aggressive eccentric contractions of the quadriceps produce significant anterior tibial translation and can injure the ACL or permanently stretch out an ACL graft (DeMorat et al., AJSM, 2004). Additional studies show quadricep-intensive activities should be avoided at joint angles, particularly the last 30 degrees of extension, when strains are at a maximum. DJO™ has developed a tool to address maximising ACL and ACL graft protection in these “at risk” positions.

Small knee flexion angles at initial contact during landing tasks may contribute to ACL injuries. The FourcePoint™ Hinge can be used to control joint range-of-motion by increasing the knee flexion angle during landing to result in a decrease of anterior shear force on the ACL by 9-13% (Garret and Yu, AJSM, 2004).

The DonJoy® FourcePoint™ utilises a spring mechanism in the hinge to apply gradually increasing resistance during knee extension. The resistance engages in the last 25 degrees of extension (relative to the extension stop).

Three adjustment settings on the hinge allow for varying the amount of resistance to meet the specifications of the physician’s protocols and the patient’s comfort. The hinge may also be turned “off” for no resistance or “on” for resistance.

The resistance serves three critical roles:

  • First, it reduces the time spent near full extension or in the “at risk” position.
  • Second, it increases the posterior load applied by the brace on the tibia to prevent anterior tibial translation.
  • Third, it eliminates the extension shock felt when a patient extends into a 10 degree standard rigid stop.

FourcePoint™ Hinge Technology works to enhance DonJoy’s Four-Points-of-Leverage™ design by damping knee joint extension, which improvesthe mechanical performance of the brace and reduces shear forces at the knee. Addressing the “at-risk” position, the hinge resistance engages in the last 25 degrees of knee extension.

The FourcePoint™ hinge combined with the Four-Points-of-Leverage™ cuff and strapping design provides a more comfortable brace that reduces anterior shear forces at the knee. Decreasing anterior shear forces at the knee are beneficial for patients by reducing strain on the healing ACL graft, providing stability to an unstable, ACL deficient knee or for prophylactic use.

Chris Payne
Sunday, 25 November 2012  |  12:36

I have an old ACL injury to my right know through Motorcross which i have injured again slightly recently and find it painful to apply pressure when for example walking up stairs. I am off skiing in 4 weeks and wondered if you could advise me of the best knee brace for this activity.
I also play a lot of squash and mountain bike riding
Many thanks

Tuesday, 27 November 2012  |  17:27

Hi Chris,

Thank you for contacting us. That is a great question and one that a lot of our customers have asked in the past. As you are going skiing with an ACL injury we would suggest the Donjoy Armor with Fourcepoint Knee Brace. This is available on our website for £499.99. It is widely regarded as the ultimate knee brace for the protection of the ACL and hyperextension injuries. The brace is made from aircraft grade aluminium so it is lightweight and strong making it ideal for sports such as skiing and motorcross.

I must stress that we cannot provide medical advice and we would always recommend you consult your doctor or physio regarding which brace would be suitable for you.

The right brace can certainly transform your experience on the slopes from a cautious and tentative one, to an enjoyable and confident one.

I hope one our ski braces can help you enjoy your ski holiday soon.