Knee Injuries: How Common Is A Torn ACL?
A torn anterior cruciate ligament (ACL) is a common knee injury, especially among athletes in high-impact sports, or activities that involve a lot of cutting and jumping. The injury itself is often caused by a swift change in direction, which is common among basketball players. A ruptured ACL can also just be a freak accident: something that happens on a relatively routine movement.
In the case of Klay Thompson, the injury occurred after he had gone up for a dunk, been bumped in mid-air by a defender, and landed awkwardly—with his left foot externally rotated while his left knee folded inward. In this video, Dr. Brain Sutterer explains in a bit more detail the biomechanics of Klay's injury.
Thompson is not the first, and he certainly won't be the last player to sustain this type of injury. In fact, since 1970 nearly 100 players have torn their ACL, including well-known hoopers such as:
The good news is that with advances in orthopedic surgery, sports medicine, and physical therapy, a full recovery from a torn ACL is more possible than ever before.
What Is The Anterior Cruciate Ligament?
The ligaments in a human body are fibrous bands of connective tissue that fasten bones together with other bones. In comparison, tendons bind muscle to bone.
The anterior cruciate ligament (ACL) is a thick rope-like cord, about the size of an index finger, that stabilizes the knee. It's one of four main ligaments that connect the femur (thighbone) to the tibia (shinbone).
The ACL and the PCL (posterior cruciate ligament) cross within the very center of the knee joint. The medial collateral ligament (MCL) runs along the inner part of the knee; and the lateral collateral ligament (LCL) traverses the outer part of the joint.
The take-home point here is that an ACL rupture seriously compromises the anterior/posterior stability of the knee joint, but why is this?
Ultimatly, this is because the ACL and PCL work in tandem to prevent the femur (thigh bone) and the tibia (shinbone) from sliding forward and back relative to one another. When healthy, these two ligaments allow the knee-joint to properly hinge, and an athlete to engage in front-to-back movements, while keeping the bones of the upper leg and lower leg optimally aligned.
Signs & Symptoms Of An ACL Injury
Some signs and symptoms that may indicate an ACL injury include:
Feeling unstable or wobbly when walking
An inability to put weight on the affected leg
Swelling in the knee joint within 24 hours of the tear
Pain, which may be intense
Many people report hearing a popping sound when the ACL ruptures, though this isn't always the case. Others experience the knee-joint feeling much looser than it was before the injury.
It's also possible, however, for people with more minor ACL tears to not even notice anything different as it all depends on the severity of the injury.
If you injure your knee, during a sporting event or any other time, it's best to stop all activity (to prevent further injury) and see a doctor as soon as possible. Avoid putting weight on the injured knee, apply an ice-pack and elevate the leg to minimize swelling.
Surgery To Repair A Torn ACL
A fully ruptured ACL typically requires surgical repair as the first step in the healing process. The surgery is usually not performed until a few weeks after the injury, which allows time for the initial swelling and pain to subside.
A team's doctor or trainer may recommend to an elite athlete that he or she do some "prehab" (i.e. pre-surgery rehabilitation) with a physical therapist in the weeks prior to the surgery in order to strengthen the injured knee and supporting muscles prior to the operation.
The surgical reconstruction of the ligament often involves using tissue from another part of the patient's body (e.g. the patellar tendon or hamstring) or from a cadaver. This new tissue is then surgically grafted onto the femur and tibia to augment or replace the damaged anterior cruciate ligament.
Overall, it generally takes 9-12 months for the surgical ACL graft to fully attach and develop its own blood supply. During this time, physical therapy and rehabilitation routines are engaged in, with progressing levels of challenge, to support the gradual healing of the joint and surrounding muscle groups.
As mentioned above, the hope and expectation for Klay Thompson is that he'll make a full return to his All-Star status.
Rehabilitation Of Torn ACL After Surgery
Recovery from ACL surgery can take anywhere from six months to a year. Active rehabilitation via physical therapy is required to help the knee to heal and to:
Reduce pain and swelling
Restore range of motion
Regain strength in the knee as well as the thigh and shin muscles
Prevent atrophy, i.e. the breakdown of muscle tissue
Along with strengthening the thigh and shin muscles, it's also important to strengthen the outer hip and hamstring muscle (back of the thigh) to provide additional support to the ACL. Overly strong quadriceps or particularly weak hamstrings put the ACL at risk.
Klay Thompson's Road To Recovery
Like any athlete coming back from this kind of injury, Klay Thompson's road to recovery from his ACL tear will progress in stages as Colin Hoobler of the Oregonian writes:
"Immediately after surgery, Thompson will start bearing weight on his left knee, along with knee range of motion (especially extension) and "safe squats" … Gaining and maintaining full left knee extension will be crucial to prevent scar tissue forming within the knee joint (called a "cyclops lesion"), which would require surgery to remove."
Also important during the initial stages of rehab is to control swelling in the knee, in order to reduce pain and facilitate a more rapid recovery. This will likely be accomplished via the three-part strategy of (1) keeping Klay's left leg elevated, (2) applying ice, and (3) using anti-inflammatory medication.
As mentioned above, strengthening the hip muscles and hamstrings, as well as the thighs and lower-leg muscles, is of central importance to the recovery process. This sort of balanced muscular development of the entire lower body helps protect the ACL and reduce the risk of re-injury. So, this will no doubt be a focus of the intermediate stages of Klay Thompson's rehabilitation.
Some examples of exercises that Thompson could engage in to accomplish this are:
Passive knee extensions to strengthen quadriceps
Heel lifts to strengthen calf muscles
Half or full lunges to strengthen the hip and thigh muscles
Standing on one leg to enhance balance and strengthen all hip and leg muscles
Regardless of which phase of ACL rehab Thompson is in, the majority of strengthening exercises will emphasize weight-bearing, multi-joint movements. Why? Because these sorts of movements minimize stress on the new ligament, while at the same time engaging a variety of muscle-groups simultaneously, to develop proper coordination.
Stages Of ACL Rehabilitation
Following a successful surgery, and once the pain and swelling in the knee are sufficiently reduced, ACL rehabilitation typically progresses through these three stages:
1. The primary focus during the first three to four weeks of ACL rehab is on restoring range of motion—with the goal of reaching full extension (straight leg) and flexion (90-degree bend) of the affected knee. This phase will also include exercises for restoring balance.
2. Once full mobility is regained in the athlete's knee, he or she can add some strength-training exercises to the rehab sequence. Use of a stationary bike or stair-climber, for instance, can help the athlete build strength in the knee and supporting muscles.
3. Three or four months into the rehabilitation process, with sufficient muscular strength and balance regained, the athlete can then begin sport-specific training. For a basketball player, this phase will consist of functional movements like running, jumping, and cutting that mimic the activities of an actual basketball game—along with ball-handling drills, free throw shooting, and cardiovascular training.
ACL Rehab Sequence
Recovering from a torn ACL is a long-term process, and how exactly it unfolds will depend upon many factors unique to the particular athlete. That said, here are some specific exercises that are generally useful in recovering from an injured anterior cruciate ligament.
Effective ACL rehabilitation exercises to begin with include: heel slides, isometric contractions of the quadriceps muscles, and prone knee flexion.
Once the swelling has subsided, you can add more complex movement such as: passive knee extensions, heel raises, half squats, knee extensions, and standing on one leg.
For detailed instructions on a similar ACL rehab sequence, check out this excellent at-home exercise routine for healing the ACL after surgery, compliments of Loyola University Medical School. These simple effective movements will help you strengthen and heal the ACL and surrounding muscles.
And remember: receiving the support of a professional athletic trainer is always a good idea when recovering from a torn ACL or any other serious injury.