The anterior cruciate ligament (ACL) is one of the most important stabilizing ligaments of the knee. Its primary function is to control the anterior translation of the tibia (prevent the tibia from traveling too far forward). This particular tissue is vital to joint health, everyday living, and athletic performance. But as important as the role of the ACL is to performance and function, we are still in the midst of an ACL injury epidemic.
ACL injuries are one of the most common sport related injuries within the United States, with injury rates reaching up to 200,000 per year. The most common cause of this injury is due to noncontact athletic movements (landing, pivoting, cutting, and jumping). Second to this are contact related sport injuries (ie. Lateral blow to the knee), frequently stemming from American football. An ACL injury can not only end a season or competitive career, but also effect normal activities of daily living (2).
According to the American Orthopedic Society for Sports Medicine, athletes overall are 6 times more likely to have a re-injury of an ACL after returning to their sport as opposed to healthy individuals (people who do not participate or go back to sport. Another study shows that one in four athletes who return to play suffer from a second knee injury. Furthermore, over 30% of the athletes that returned to play experienced a second injury within 20 games or practices after returning to their sport. The athletes who return to play are likely to re-injure the new ACL graft, or tear/rupture the ACL in the contralateral knee (opposite knee) (3).
ACL Injury Rehabilitation
Depending on the severity, the recovery time can range from 6 to 12+ months. After the injury, the athlete may undergo surgery followed by extensive rehabilitation. Once the surgery is complete, the new ACL graft tissue has to rebuild itself and attach back to the bone. As a result of the long recovery phase with limited physical activity, it can lead to decreased athletic performance, strength, coordination, muscular atrophy, and loss of lower extremity stability.
As soon as the athlete is ready for the rehab process, the health care professional needs to take a strong lead on helping the athlete get back to their best functioning levels. This can greatly increase the probability of the athlete continuing their sporting career and improving quality of life.
The rehab process is also vital for enhancing the overall strength and stability of the surrounding knee musculature. Sometimes, time spent away from competitive play and focusing on rehab, intelligent strength work, and injury prevention, allows the athlete time to work on their weaknesses.
3-Phase Post-ACL Injury Return To Play Solution
The main variable we need to focus on post-surgery is preventing the injury from reoccurring. To have the most successful outcome, we need effective and intelligent strategies which prioritize rebuilding the neuromuscular system while remaining pain free.
The structure of the rehabilitation process should contain exercises and training principals focused on mobility, strength training, plyometrics, balance, and agility drills (ex. landing, jumping, planting, and changing direction). This is especially important for athletes playing higher ACL risk sports such as football, basketball, and soccer.
Building a quality strength program with an emphasis on injury prevention is key to an athlete’s success and should resemble the following methodologies:
Phase 1 – Mobility
At the beginning of the rehabilitation process, establishing proper mobility as soon as possible is vital to the continuation of correct movement and quality strength training. Mobility is the key to proper body mechanics and achieving stable exercise positions. During this phase, the athlete should be focusing on pain control, obtaining full range of motion, muscle activation, and proprioception.
Phase 2 – Stability
Once adequate mobility is established and maintained, the athlete can now focus on stability exercises to help protect and strengthen the joint (4). Enhancing stability within the joints increases their ability of to resist movement from an outside force or exert their own movement. This is one of the most important aspects to the post rehabilitation process since adequate stability is needed to build resiliency and long term joint health.
As the range of motion is increased, strengthening the muscles around the joint, balance training, and the reintroduction of functional movement should be addressed.
Phase 3 – Strength & Hypertrophy
As soon as proper movement is achieved, the primary focus is to build up the integrity of the weight bearing joints and surrounding musculature. Even though the knee joint is the “main focus”, we still need to enhance the proximal joints in the kinetic chain to increase overall resiliency. We have to be aware that the body works synergistically to perform at optimal levels, not in isolation.
To get the athlete fully prepared to return to play, they need to begin training compound movements which promote hypertrophy, strength and power throughout the whole body.
These compound movements should then be accompanied with unilateral and some isolation work to reduce strength imbalances, muscle atrophy, and further enhance stability and injury prevention.
Even though all the muscles throughout the legs are highly important for support and stabilization of the joint, there should be strong focus on hamstring development. Since the hamstrings prevent further anterior translation of the knee, they act as a safe guard and should get some extra attention during rehab and strength work.
Unilateral exercises are going to serve as a staple to our strength and injury prevention strategies for an ACL injury. This method of training places a high emphasis on specific muscle groups, the joints, connective tissues, and stabilizers that are extremely important for joint health and functionality.
The lunge is one of the best movement patterns to train when rehabbing from an ACL injury. To rebuild strength and stability after this type of injury, it is extremely beneficial to incorporate eccentric focused split squats.
The setup and execution of this exercise is very important to yield proper results and prevent re-injury. So, let’s review this particular method to make sure we get the most benefit for optimal performance.
How To Set Up & Perform Eccentric Split Squats
Standing in place, brace the core musculature and pack the shoulders to promote good posture and solid kinetic chain.
Step one foot back, placing you in a tall lunge position. Front foot is planted firmly on the ground actively pressing into the floor.
The back foot is dorsiflexed and planted firmly in place.
Flexing at the hip and knee of the front leg, descend down to the floor until the knee of the back leg almost comes in contact with the floor.
Place a 4-6 second time emphasis on this part of the movement (eccentric) to achieve the desired training effect.
Then extend at the knee and hip of the front leg to return to the starting position at normal speed.
Complete the designated amount of repetitions with the accentuated eccentric focus on each rep before switching to the other leg.
* To place a higher emphasis on the glute and hamstring, you can slightly lean forward for increased activation of those muscles.
This exercise places high emphasis on the quadriceps, glutes, and hamstrings which are vital to the health and function of the knees, as well as other surrounding connective tissue. You can also increase the intensity by adding an external load such as a dumbbell, kettlebell, or barbell. Not only is this variation superior for rehabilitation, it can also help prevent the injury from occurring in the first place.
Accentuated Eccentric Training
Your body can handle 1.75 times more weight eccentrically than it can concentrically (1). So, by exaggerating the eccentric portion of the movement, the higher stimulation will promote greater muscle hypertrophy, and stronger connective tissue. As a result, the higher amount of muscle growth will bring about increased levels of strength and power to not only prevent injury, but also boost sports performance. Furthermore, eccentric training also increases flexibility which aids in proper function and biomechanics.
Split squats strengthen the lower portion of the kinetic chain and make sure the knee remains stable above the foot throughout exercise. Boosting strength and stability at the knee is extremely important for preventing unwanted movement at the joint. Thus, decreasing the overall risk of ACL tears/ruptures and other injuries.
Eccentric split squats should be trained in various rep ranges focusing on strength, hypertrophy, and muscular endurance to make sure the athlete is ready to return back to play. Slowing down the speed of the exercise will help limit any movement compensation and allow the athlete to create stability in all ranges of motion.
Injuries often occur when an athlete is fatigued from continuous play and is no longer able to maintain correct form. Therefore, once adequate strength has been established, working in the 15 plus rep ranges to increase muscle endurance will help avoid early fatigue and possible injury.
Preventing & Protecting Against ACL Re-Injuries
Getting an athlete to return to play after experiencing an injury is a feat in itself. However, if we can further enhance performance post injury, or aid in the prevention of it, we can have a profound effect on helping our athletes be successful. As professionals, we should be applying various techniques and methodologies to provide the best possible outcome for our athletes. Incorporate this training method into your exercise programming and help them regain optimal performance.
About The Author
Tim Danchak, BS, ACSM-CPT, FTS
Tim is a strength coach, wellness instructor, and functional training specialist in North Carolina. His primary focus is working with general and special populations to regain proper movement mechanics and improving total body strength. Tim’s passion is focused on enhancing overall quality of life and pain free performance for his clients.