At first glance, your knee may not look like a very complicated part of the body. But, it is actually a remarkable piece of architecture. The knee is the largest joint in the body and is made up of 3 different bones, 4 ligaments, and 2 tendons. All of these work together and allow us walk, run, and jump with almost zero effort.
Unfortunately, the knee is also the most vulnerable joint in the body. It bears an enormous amount of weight and pressure from our day-to-day activities. Consider that when you walk across level ground, the force on your knees is the equivalent of 1½ times your body weight. That means a 200-pound man will put 300 pounds of pressure on his knees with each step1. Add an incline and the pressure is even greater: the force on each knee is 2-3x your body weight when you go up and down stairs, and 4-5x your body weight when you squat to tie a shoelace or pick up an item you dropped1.
The part of the knee that is most susceptible to injury is the anterior cruciate ligament (ACL). This is a band of tissue that holds the bones together within the knee and helps give it much of its stability. Because of this, ACL tears happen all the time, and it’s not just in athletes. Millions of us will have an ACL tear, so here are a few things you should know about them:
1- What causes an ACL injury
Although ACL injuries can occur after any traumatic event, they’re usually caused by one of three actions:
- An injury that happens when the knee is hyperextended (straightened) and a pivot occurs at the same time. This action can occur without any contact meaning you don’t have to be knocked over or pushed (if you’re playing contact sports) to get it.
- A bad landing after a jump (especially in basketball) which positions the knee at an awkward angle
- Simply turning the body while slowing down
2- Having an ACL injury or tear does not necessarily mean surgery
The treatment for most ACL tears is surgery but that does not necessarily mean it is necessary in all cases. Depending on the nature of the injury, the amount of damage your knee has sustained, and your lifestyle (how active you are), surgery may not necessarily be the first choice that your doctor recommends. For those who can get away without surgery, however, will still need an intense period of rehabilitation and physical therapy.
3- According to some studies, once you suffer from an ACL injury your chance of developing osteoarthritis in later life increases by 50%2
The knee is a very delicate joint. Once it sustains a significant injury like an ACL tear, it is difficult to get it back to its pre-injury state. This does not mean that your knee won’t be fully functional. It simply means that it will be weaker than it was before. This increases the chance of developing osteoarthritis (wear and tear of the knees) in coming years.
Things you can do to help reduce the chances of developing osteoarthritis:
- Start taking care of your knees right now. That means being mindful of any high-impact sports that you take part in. Be aware of the kinds of activities that place undue stress on the knees
- If you have an ACL tear, make sure it is completely healed before going back to any moderate sports (ie. running, weight-lifting)
- Make physiotherapy a priority. After your first few sessions with a registered physiotherapist, be sure to keep up with the home exercises you’ve been taught. This will keep the knee mobile, flexible, and healthy for a longer period of time.
- Use suitable exercises to build up the muscles, tendons, and ligaments that support the knee joint.
4- Women have an increased risk of ACL injury
Due to differences in anatomy and muscle mass, women are more likely than men to develop an ACL injury2. For women who are physically active and engage in many sports, be sure to protect yourself against an ACL injury. For tips on how to do that, consider the options below.
5- It might be possible to prevent a torn ACL
You can never predict exactly how your lower body will move, rotate, or shift during a split-second maneuver that can lead up to an ACL tear. But, you can decrease the chances of one happening. This can be done by performing training drills that work on your balance, agility, and power. By teaching the muscles that surround the knee how to react when placed under stress, this muscle memory may help protect the knee joint when a potential injury situation exists3.
1- Harvard health. Why weight matters when it comes to joint pain. https://www.health.harvard.edu/pain/why-weight-matters-when-it-comes-to-joint-pain
2- Harvard health. ACL (Anterior Cruciate Ligament) Injuries. October 2014. https://www.health.harvard.edu/diseases-and-conditions/acl-anterior-cruciate-ligament-injuries-
3- eMedicine Health. Torn Anterior Cruciate Ligament (Torn ACL or ACL Injury). http://www.emedicinehealth.com/torn_acl/article_em.htm