Influence of Functional Knee Bracing on ACL Strain Biomechanics
In any sport there is a risk of injury. Pushing your physical limits whether it is on a football pitch, tennis court or athletics track will put you at risk of injury. However, in sports where there is a fair portion of risk in the actual activity itself, failure in having perfect judgment may cause loss of control or a crash and with it often quite serious injury.
Sports also differ in how they view injuries and how they affect participation. David Beckham broke a small bone in his foot and it was considered close to critical. However, over the pond Ryan Hughes was strapping himself up to get back out for a second moto after breaking his leg in the first...
If there is one 'problem area' in the body of a motocross rider, the knees would certainly be a top candidate. Many riders suffer from serious knee problems and surgery is quite common. If it wasn't for serious knee damage, RC would have been on the line in Anaheim to defend his crown, Pichon wouldn't have had his season cut short and Pastrana may still be on two wheels and not beating Porsche test drivers on the asphalt?
So why is it knees take such a battering and what exactly is this 'Cruciate Ligament' people talk so much about? The knee is primarily a hinge joint flexing and extending the leg. Ligaments maintain the stability of the joint and resist rotation of the joint and also the relative movement of the tibia (shin bone) in relation to the femur (thigh bone). There are four critical ligaments involved in this - the Anterior and Posterior Cruciate Ligaments (the name comes straight from the Latin as they 'cross' each other within the joint) and the Lateral and Medial Collateral Ligaments. The most common injury of the knee is a tear to the Anterior Cruciate Ligament (ACL). This occurs when the leg is hyperextended (straightening of the knee beyond its normal range of motion), when there is a rotation force around the knee or when the tibia is forced forward.
As you can see, in the sport of Motocross any of these situations listed is not uncommon and the chances of injury are high. Another reason why injury to the knee is becoming more commonplace may be due to the effectiveness of modern boots. They are now so stiff and good at protecting the ankle joint that any force that would rotate the ankle is just transmitted up to the next joint (the knee!) Think of catching your toe in a rut as you corner, your foot may be twisted, but this twisting force is not absorbed by the ankle but transmitted straight to the knee and this vulnerable area suffers the damage.
So how do we deal with this problem? There are some things that as a rider, you can do that will help protect and prevent from knee injuries. Strengthening the muscles that stabilize the knee joint is very important as this offers a better functioning joint. So training of the Quadriceps, Hamstrings and Calf muscles is important in 'strengthening' the joint. Another area to look at is flexibility. Increasing range of motion of the joint will help prevent damage to it, so aim to increase movement, flexibility and range of movement in your knee.
Knee braces are very popular and are used my many riders to protect the knees, aid rehabilitation from an injury, or to prevent from any possible ligament damage. So are knee braces the way to go then? Pro's endorse them and amateurs fork out up to £500 for each carbon fibre and metal mechanical cage. It is big business and in one American publication I saw no less than 6 different companies advertising similar products in one issue.
The ultimate usefulness of a knee brace is dependant upon its ability to protect the ligaments of the knee. It must either shield or share the forces put onto the joint while still allowing for a full and normal range of movement. One may immediately assume that with the use of lightweight, stiff composites a strong structure can be made to sufficiently protect the knee. That is partly true. The problems arise when we try and secure the brace to the user. If we did not have muscle and soft tissue to worry about the interface between the brace and the 'patient' would be secure and there would be no movement once attached. This would give an effective means of protecting the joint. However, we all have a layer of soft tissue that causes problems when it comes to securing the brace and it is the inability of the brace to be mounted securely to this soft tissue that has been shown by many scientific studies to be the major flaw in the effectiveness of knee braces. The brace ends up slipping or moving around. The braces must also apply a sufficient lever force to counteract the force put upon it. So the longer the lever, the more effective it will be. Braces however have quite short levers (mainly limited by making them wearable and comfortable) so they can only offer a certain amount of control.
It is also interesting to read the marketing material for braces, EVS carefully state on their website that 'knee braces are meant to provide the user with a level of protection...' which isn't exactly stating a lot at all.
The scientific literature is very mixed on how effective braces are, some studies have shown that muscle activation is reduced and delayed, causing more reliance on the brace and have shown other negative views on their effectiveness. Some have shown positively that some braces can offer reduced strain on the ACL and so can be considered to offer a level of protection to the user. There are other ways in which they help though. One must not discount the placebo effect of the braces on the subjective feeling of protection and security that they offer the user. Numerous studies have shown while performance and protection of the joint is not improved, the subjective feeling of security felt by the user is increased. In a sport that markets braces along side boots and chest protectors, the use of athletes in their promotion is integral. For the customer this may often mean that after buying a product that they believe the athletes use themselves, they feel better protected. If the rider is returning from injury, braces remind them that they should be careful how they ride. Also, with some braces, they offer good protection to direct impact blows to the knee and this is very relevant for crash situations where there may be direct impact between your knees and the bike or ground.
Suffering an ACL tear will obviously impair the joint function and because of this it is often operated on. Because of its fibrous nature is hard to stitch it back together - a friend of mine was told by one orthopedic surgeon that it is like stitching two toothbrushes together. So it is often replaced with a tendon: a portion of the patellar tendon, or from a tendon of the hamstrings.
Rehabilitation is very important to regain joint stability, full range of movement and reduce the chances of secondary injuries or pain. There are many exercises to follow - that is beyond the scope of this article, but the main point to raise is that adherence is key. If you don't do the exercises you will have a deficient knee joint. This is especially important if you have a brace as the brace often causes the muscles to 'rely' on it and as mentioned earlier muscle activation is delayed when wearing a brace. A good sports injury clinic will advice you appropriately and have a good appreciation of the desire for you to get back out on the bike, so won't just suggest taking up bowls...
