Dynamic Knee Braces
The concept of dynamic bracing is not new. Gary Bledsoe, of Bledsoe Braces, developed the technology in 1996, and since the merger of the Bledsoe Bracing Company and Breg Bracing Company this technology is a unique feature to Breg Bracing.
The key principle of Dynamic Knee Braces is to use biomechanical leverage to apply force only when support is needed.
There are three types of Dynamic Knee Braces:
1. Ligament Knee Braces
2. Osteoarthritis Knee Braces
3. Patellofemoral Knee Braces
The force required to fail an Anterior Cruciate Ligament (ACL) is very high, and approximately 80% of ACL injuries occur without any external contact. This means that the ACL usually fails because of internally generated physiological forces rising too high and too fast for the muscles to react and recruit.
When it comes to ACL injuries, there are two main approaches to treating the injury. You can go the conservative approach, which involves physical therapy and rehabilitation post injury. Of course this would involve living with an ACL deficient knee, and may impact daily living. The second approach would involve surgical intervention through reconstruction or repair.
Four things that ACL deficient patients have difficulty doing:
1. Stopping quickly
2. Running downhill
3. Landing after jumping
4. Moving laterally
Whether a patient has been treated conservatively or surgically, there is still a timing problem in gait mechanics of the knee joint.
During extension, especially during the last 30 degrees, the quadriceps muscles fire, which cause an anterior translation of the tibia relative to the femur. And because of the disruption in the knee joint, whether due to being ACL deficient or reconstructed, the hamstrings fire too slowly to react. This may be the result of a lack of neural activation. In a normal knee, the hamstring response time is between 40-50ms. In an ACL deficient or reconstructed knee, the response time is closer to 100-150ms. These reduced response times can last many years after injury.
As a result of these mechanics, the tibia will be subluxed (out of position) right before foot strike, which will create a level of instability and discomfort at foot strike for the patient.
So How Do Dynamic Knee Braces Impact The Timing Issue?
The key principle in dynamic bracing for ligament injuries is the use of muscle power and leverage to apply a specific load during the moment of need. In an ACL-specific brace, the dynamic force is applied in a posterior direction against the tibia in the last 30deg of extension. The result of using this dynamic force is an increase in control of the knee joint just before foot strike, and therefore more stabilization of the knee.
Osteoarthritis is a type of joint disease that involves the deterioration of cartilage that surrounds the ends of bones, and the deterioration of the ends of the bones themselves. Mechanical deterioration of the knee joint often occurs due to misalignments in the joint. This results in a loss of cartilage more on one compartment of the knee than another. 80% of patients with OA of the knee joint will have more deterioration on the inside compartment of the knee.
The causes of osteoarthritis typically include:
1. Trauma or Injury
2. High Weight
3. Activity Level
4. Amount of overuse
Research also shows a link between long-term instability from ligament injuries and meniscal injuries, and early onset of osteoarthritis.
So What is OA Bracing? What Do OA Knee Braces Do?
OA knee braces use corrective forces to align the knee joint, and in doing so, reduce the discomfort caused by OA.
As a result, two things can occur:
1. Return to normal activity
2. Slow the progression of OA
The symptoms of OA occur when weight-bearing. One of the unique features about dynamic bracing is that it will only apply a load when it is needed specifically for support or leverage. What that would mean for the typical OA patient is no force would be applied in a flexed position, making it easier to sit in a car, or sit at a desk at work for long periods at a time. Because the mechanical load is only being applied during moment of need, the brace will be more comfortable to wear, and can prolong usage time.
The patella (knee cap) is the body’s largest sesamoid bone. A sesamoid bone is a bone that lies within a tendon in the body, and is used to increase mechanical efficiency of a joint. The patella, in particular, is able to increase the efficiency of the knee joint by as much as 50%. Because of its large surface area, it also allows for enhanced pressure distribution. This allows the knee joint to easily manage the forces associated with daily walking. The forces that are involved with running and higher impact sport and activity, however, can often result in patellofemoral pain syndrome.
Research on patellofemoral syndrome shows that the most likely biomechanical cause for pain is a lateral shifting of the patella between the femoral condyles. This would result in irritations on the underlying surface of the patella, causing inflammation and swelling around the knee joint.
So How Do Dynamic Patellofemoral Knee Braces Work?
Dynamic patellofemoral braces use a mechanical force to progressively increase the amount of lateral (outside) compression applied to the patella when needed most. The knee brace provides dynamic stabilization with increasing knee extension; meaning from 30 to 0 degrees of knee extension, a hinge engages and provides a soft tissue lateral wall, which maintains the patella within a normal range of tracking.
Arthritis & Injury Care Centre provides a wide range of dynamic knee braces in Halifax, Dartmouth, Saint John, Fredericton, & Moncton. Contact us today for your free consultation!
Russell Cattoor, BScKin, C.Ped (C)