What is Proprioception?
Proprioceptors are sensory receptors located within joints, muscles, and tendons that relay information to the subconscious and conscious parts of the central nervous system based on your awareness in space and during movements. They are sensitive to pressure and tension which gives the brain feedback on the position of body parts in space and during movement. Most of this proprioceptive information is processed at the subconscious level so we do not have to spend conscious thought towards maintaining posture or even positioning of body parts. At least, not until you have ACL surgery.
The ACL is a special type of proprioceptor called a mechanoreceptor. The ACL tells your body where and how to work during movements like cutting or pivoting, and any lag in time for feedback to the brain leaves you in a vulnerable position allowing higher risk of ACL injury. After suffering an ACL injury, it is essential to increase your proprioceptive awareness in order to fully rehabilitate the injury and help to prevent further injury to the ACL or injury to the other knee. This is another reason allograft or cadaver used for ACL grafts is less than ideal for an athlete. How do expect to regain the same movement control and reaction time using a dead tissue without any working mechanoreceptors?
After an ACL injury it can be very hard for an athlete to restore their normal reaction times and relearn their proprioceptive ability or the awareness of their knee in positions and movements. Sometimes this is thought of as a mental block or being scared to perform certain movements again following an injury but it has just as much to do with the decreased neuromuscular awareness stemming from the damaged or missing mechanoreceptors as it does the brain itself. This can play a huge role in the risk of reinjuring your ACL because a decrease in proprioceptive abilities of the knee can contribute to improper cutting, jumping, or landing mechanics further contributing to your risk of ACL tear. Remember, about 70% about ACL injuries are noncontact injuries but with proper strength training programs and coaches working with athletes on jumping, landing, and cutting movements a lot of these injuries and reinjures can be prevented.
Balance training on BOSU balls, foam pads, and balance boards are a huge emphasis during ACL rehabilitation. Advancing yourself to working on reaction time training like quick changes in direction and decelerating after sprinting will be the best way to prepare for the demands of sport after surgery. Reaction training is essential in regaining full proprioceptive awareness and ramping up the tempo for reaction training to mimic the demands of the athlete’s sport will help to decrease their subsequent injury risk.
Creating an unstable environment, like shown in this video, is a great way to begin advancing your rehabilitation and incorporates more muscle recruitment. Starting with a simple single leg balance is great after surgery, but there are many creative ways to advance these exercises safely over time.