One of the more common injuries to the knee is tearing the Anterior Cruciate Ligament (ACL). The ACL connects the top front portion of the tibia (shin bone) to the bottom rear part of the femur (thigh bone). Ligaments are tough bands of fibrous tissue that connect bone to bone. Compared to muscles, ligaments stretch very little and do not have as many blood vessels. This means that if too much force is applied to a ligament, it will become sprained, tearing rather than stretching. With few blood vessels in the tissue, the limited circulation means a lot longer recovery process. Often surgery is used as a way to reattach torn portions back together. In some cases where the ACL is unrepairable, surgeons will use ligaments from other areas of the body, or from a cadaver, to create a completely new ACL.
The cause of ACL tears is mainly due to the tibia and femur moving too quickly away from one another. This can happen when both bones rotate in opposite directions. It can also happen when they rotate in the same direction, just at different rates of speed, as when changing directions quickly. What should ideally control, or decelerate, knee motion are the muscles and fascia which surround the joint. Hamstrings and calf muscles help decelerate knee extension and internal rotation, while quadriceps and gluteals help decelerate knee flexion and external rotation*. If the tissue does not slow down such force, the ligaments will often take the brunt.
When a person is standing, and the knee joint is not in it’s proper structural position, the surrounding muscles will either shorten or lengthen to accommodate the position. Muscles that are too long will not have the capacity to properly shorten back to a normal resting length. Muscles which are too short will have difficulty lengthening back to a normal resting length. Neither scenario is ideal. Over time, if this position is reinforced, the length of the muscles become normalized, the imbalances are maintained, and the knee resides in a compromised, weakened state. The ability to decelerate force wanes.
There are several approaches in the fitness and rehab world that claim to help prevent future ACL tears, but most do so by avoiding the movements where bad things can happen. The trouble with this approach is that the neuromuscular system never gets to experience what to do when the knee travels into “foreign territory” and how to get out of it. It would be similar to telling a child never to cross a busy intersection. Then, one day a ball bounces out into the intersection and the child, without thinking, charges after it. The potential for major harm is very high. A better approach would be to teach the child how to cross safely so, no matter which street they cross, the chance of success is almost guaranteed. Therefore, we want the knee, and it’s surrounding tissues, to gain the experience of all types of movement. Guide the joint into flexion and rotation and guide it back out again. The nerve endings will feed vital information to the connective tissue to take pressure off the ligaments.
As you can imagine, I could write pages and pages on this topic but I will cut it short and get right to the movements which can be utilized as a means of bulletproofing the knee joint in order to reduce the likelihood of ACL tears. These movements will encourage muscles which are “locked long” to shorten a bit, while encouraging the opposite to the muscles “locked short.”
#1 Single Leg Toe Taps - Balance on one leg while reaching as far as possible forward, pain free, with the opposite foot. Next, reach forward and diagonally, then reach out to the side perpendicular to the direction the standing foot is pointing. Be sure to return back to the starting position after every reach. Repeat this on the opposite leg. Determine which leg was more challenging and perform an additional set on that leg.
#2 Single Leg Rotational Balance - Balance on one leg while the opposite foot is resting toe down out to the side. Rotate in the direction of the big toe and descend gently as the knee flexes and rotates toward the opposite foot. Be sure to keep the torso tall and relaxed. Reverse directions and see if you can experience the knee fully extending as the arch of the standing foot begins to draw upward. Continue to rotate left & right over the standing leg and explore a pain-free end range of motion each way. Preventing ACL Tears
#3 Clock Lunges - In a tall, standing position, step with one leg out to each of the hours on a clock. Left leg stepping counterclockwise while right steps clockwise. Take large steps but do not step so far that you experience pain or that you cannot push back to the starting position.
#4 Shift & Reach - Step back with one leg. Shift the pelvis straight back, pain-free, as far as possible. As the pelvis shifts back, reach forward with both arms as far as possible. The pelvis and torso should travel in opposite directions at the same time. The forward leg will straighten at the knee, and the foot will flex upward so only the outside of the heel remains in contact with the floor.
*Most anatomy books will state the opposite when it comes to knee mechanics and rotation because the way anatomy was studied was with a body laying on a gurney, not while the body was in motion. These two events (lying on a table and moving upright) will bring about two different outcomes and understandings of biomechanics. It is this confusion and incomplete information about movement which still prevails and is the cause of ineffective rehab strategies and conditioning programs to this day. When a body is in motion and the knee flexes and travels medially (toward the midline of the body) the knee joint is externally rotating. As the knee begins to extend (straighten) the joint internally rotates. This is because the femur moves much faster than the tibia.