Devon McGregor, National Post · Feb. 25, 2009 | Last Updated: Feb. 24, 2009 7:02 PM ET

Over recent months, many members and staff at our club have become familiar with the letters ACL — sometimes even painfully aware.

The anterior cruciate ligament (ACL) is one of four ligaments that hold our knee, the largest joint in our body together. All work together to ensure the structural integrity of the knee, as well as stabilizing it for an appropriate range of motion. Ligaments connect bone to bone, across a joint. 

The four ligaments are divided into two groups: cruciate and collateral. Of the four ligaments, the ACL is the one most frequently torn, especially in women. 

The function of the ACL is to provide stability to the knee and minimize stress across the knee joint by preventing excessive forward movement (flexion) of the lower leg bone (tibia) in relation to the thigh bone femur) and limit rotation of the knee. 

Damage to the ACL (tear or rupture) results from over-stretching of the ligament, often a sudden stop and twisting motion of the knee, slowing down while running, landing from a jump or a force/impact to the front of the knee. The symptoms can be: 

-Partial or a complete tear or rupture.

-Some people, but not all, may express feeling or hearing a “pop” at the time of the injury. 

-It is often injured together with other structures inside the knee joint, primarily the meniscus. 

-Swelling to the knee and mild to severe pain. 

-Instability or a sensation the knee is “giving out.” This is because the femur and tibia are literally “sliding” against and apart from each other. 

If the ACL is fully torn, and depending on the individual’s age and activity level, a surgeon may recommend surgical repair or reconstruction, a complicated procedure. A successful repair involves completely replacing the torn ligaments, and there are a number ways that this can be done, including grafting (using other fibres and tissues, such as the hamstring or patellar tendon). 

Dr. Darlene Buan-Basit is the chiropractor and pilates instructor at Balance Fitness. She is thirtysomething and athletic. She suffered a complete tear of her right ACL about 1½ years ago while riding her bike. The front wheel got stuck in a Toronto streetcar track and her knee lost the battle. She felt the tell-tale “pop.” Due to her age, activity level and profession, her surgeon recommended a complete knee reconstruction. The surgery process involved using her hamstring to rebuild her ACL. She thanks her rehabilitation and training sessions for her recovery. 

In Buan-Basit’s case, reconstruction was necessary because of the severity of soft tissue damage — she had also torn her medial meniscus and medial collateral ligament, “the unhappy triad.”

There are two menisci in our knee; each rests between the femur and tibia. They are made of dense cartilage and form to the surfaces of the two bones. Their function is to equally distribute body weight across the knee joint. The most common environment for a traumatic meniscus tear is when the knee joint is flexed and then twisted, which is what happened in Buan-Basit’s case. 

A client, Shelley, was a little more fortunate. Her injury was sustained due to ski bindings that didn’t release. MRIs demonstrated a partially torn ACL and meniscus in the left knee joint. Her orthopaedic surgeon offered two procedures, recommending the one that would allow her knee to bend easier, allowing her to continue activities like yoga, which requires full knee flexion. While waiting for the MRI results, we worked very hard to regain movement in her left knee and actually to re-pattern her movements; reminding the knee of how it’s supposed to function.

Her surgery was scheduled, but “then something happened to change my mind”, she says. “I was speaking to my cousin, who is the head orthopaedic surgeon at Sunnybrook Hospital, and he urged me not to have the operation.” He felt that her age — being over 50, with an ACL only partially torn, she did not require surgery. There could be complications, such as ongoing stiffness, pain and limited knee flexion. “Because I am very active, he suggested I wear a brace on my knee when doing certain activities.”

What he said resonated with her, and she cancelled the surgery. “I have never looked back,” Shelley says. “My body has reorganized itself and I have not had any incidence of instability with my injured knee and feel that I have come back stronger and more aware of how I should move so as not to hurt myself.” She has recently started jogging again after a 25-year hiatus. 

It isn’t a coincidence that these two examples are both drawn from the injury experiences of women. There is ongoing research that shows that women experience ACL injuries three to 10 times more frequently than men. The reasons vary and are so far unproved. However, some theories are: 

Hormones Ligaments, like many other tissues, are affected by hormone levels. ACL injuries are known to most commonly occur in the pre-ovulatory phase in women. 

The ACL itself On average, women have a slightly smaller ACL. The intercondylar notch, the channel where the ACL passes through the knee joint, is slightly narrower in women. 

Landing Women experience increased odds of ACL damage during impact from landing. They tend to have muscle activation patterns in which the quadriceps predominate and decreased knee stiffness appears to occur. That is, women tend to land more stiffly than men.

Good ACL stabilization requires neuromuscular control of the knee, which is maintained by a complex interaction of the quadriceps and hamstring muscles, as well as the nerves that stimulate the muscle contraction. To minimize susceptibility to ACL injury, training programs should focus on creating balance between the hamstrings and quadricepts. If the hamstrings are excessively weak or inflexible they may not adequately protect the ACL during a strong quad contraction. Conversely, when the quadriceps are excessively strong, relative to the hamstrings, the ACL may be torn due to a lack of hamstring “protection.” It is recommended that the hamstrings should be 60% to 80% as strong as the quads. Balance exercises can be utilized to improve the neuromuscular recruitment patterns of the quads and hamstrings.

-Devon McGregor, BFA, BSc, human kinetics, is a fitness expert with more than 18 years experience and co-founder of Balance, a Toronto fitness centre. 

info@balancefit.com