Muscle imbalances are one of the main reasons there is a higher incidence of ACL tears in females compared to males. Richard Cunningham, MD, a Board Certified Orthopedic Surgeon and Sports Medicine Specialist, works extensively in diagnosing and treating ACL injuries in female athletes. Dr. Cunningham wants female athletes to know how to train to prevent an ACL injury.

ACL Tear in Female Athletes

The incidence of ACL tears is 2 to 8 times greater in female athletes compared to male athletes. ACL tears are most often the result of a non-contact injury. These injuries are not typically due to a collision with another player. Rather, athletes more commonly tear their ACL when landing from a jump or when suddenly decelerating or pivoting. Factors to consider when assessing a female athlete’s ACL injury risk includes:

• Biomechanics – bony alignment and soft tissue anatomy
• Muscle imbalances – commonly unaddressed muscle strength asymmetry
• Overtraining – chronic overuse leading to muscle fatigue in already weak muscle groups causing poor body position predisposing to injury

Although some factors such as bony alignment cannot be altered without surgery, muscle imbalances can be addressed through your training regimen, and one’s injury risk can be significantly reduced. All of our joints have opposing muscle groups. When the muscle strength of opposing muscle groups is symmetrical, performance is enhanced and the rate of injury – including ACL tears – is reduced.  Muscle balance should be central to a female athlete’s training protocol. Let’s take a closer look.

What are Commonly Seen Muscle Imbalances in Female Athletes?

The most common imbalance Dr. Cunningham sees that contribute to ACL tears is that the muscles in front of the leg and hip (the quadriceps and hip flexors) are stronger than the muscles in the back of the leg (the hamstrings and the gluteal muscles). The quadriceps act to straighten the knee whereas the hamstrings act to flex or bend the knee. The hip flexors act to flex the hip (bring your knee toward your chest) whereas the gluteal muscles act to extend or open the hip joint and abduct the hip (raise one’s leg out to the side). To have proper muscle balance, these opposing muscle groups must have equal strength and most female athletes do not have this.

More commonly, the sports and activities that we do preferentially strengthen the muscles in the front of the leg leaving the muscles in the back of the leg weaker.

• Quad and hip flexor dominance –  When the hamstrings and gluteal muscles are weaker than their opposing muscle groups (the quads and hip flexors), the result is poor landing biomechanics. Studies have shown that as a result of these imbalances, female athletes tend to land from a jump in a knock kneed (valgus) alignment. This leads to a higher risk of ACL tears. Weaker gluteal muscles are the main contributor to landing in this knock kneed alignment. Quad dominance also causes the tibia (lower leg bone) to translate anteriorly when the quad is suddenly engaged which places increased forces across the ACL, predisposing it to tear.
• Core muscle weakness – Core muscles such as our abdominal musculature, acts to stabilize the spine and pelvis. Many female athletes have a somewhat weak core and, as a result, when they decelerate while running their upper body is posterior or behind their legs. This can lead one to not land over one’s knees and feet but rather to “land in the back seat.” As a result of this, an athlete cannot absorb the ground reaction forces across their ankle joints, knee joints, and hip joints. Rather, they land or decelerate with their knee straight or stiff legged placing their ACL at risk for tearing.
• Hormones and Muscle Mass – Higher testosterone levels allow for muscle growth. Female athletes have less testosterone. In addition, females have higher levels of estrogen and have higher levels of body fat on average. Female athletes also have on average a smaller ACL. Having less muscle per pound of body weight leads to a higher rate of ACL tears.

ACL Injury Prevention in Female Athletes

Dr. Cunningham and his medical care team recommend a fitness program for female athletes that focuses on addressing any muscle imbalances before participating in high risk sports such as soccer or alpine skiing. One of our trusted physical therapists would first measure your muscle strength in your quadriceps, hamstrings, gluteal and hip flexor muscles. Core muscle strength would also be assessed.

Most female athletes are weak in their gluteal and hamstrings. This leads to contracture of the IT band and can cause pain around the knee cap (patella). When muscles are weak, muscles try to compensate for this by contracting and getting tight. Given this, a physical therapy program typically consists of:

• Foam Rolling – Foam rolling the IT band to lengthen it and rolling tight gluteal musculature with a hard ball (such as a softball) will help release these muscles, increase blood flow to them, and reduce pain in them so that they can later be strengthened more effectively.
• Gluteal Strengthening – Lifting one’s leg off to the side against resistance (both with the hip extended and flexed) is important. Most athletes do not work on this enough and thus their glutes are weak and their landing mechanics are poor.
• Hamstring Strengthening – Exercises such as dead lifts (with your lumbar spine in a lordotic or arched alignment so it is protected) and prone hamstring curls are important to include in one’s strengthening program. Most sports are quad dominant so be sure to do these hamstring exercises and not simply quad exercises such as lunges, leg extensions and leg press.

Form – Commit to proper form. Having at least a few visits with an experienced physical therapist or personal trainer is recommended before you embark on an exercise program.

Commitment – A fitness program requires a long view. Protection of the ACL and the knee joint is an essential part of keeping female athletes in the game. Good Muscle balance can be restored through an initial multi-week program, but it also requires a maintenance program.

If an ACL tear injury is sustained, it is important for the female athlete to be evaluated and treated by an expert orthopedic surgeon specializing in sports knee injuries. Dr. Cunningham has 20 years of experience in getting female athletes back to their sport and back to competing at their same high level of  competition following an ACL injury. He is committed to getting athletes back to play as soon as possible. A critical component of Dr. Cunningham’s practice as a knee doctor is his commitment to advancing innovations in ACL surgical techniques. As such he has been one of the first to utilize quad tendon grafts to reconstruct ACL’s and was an early pioneer in repairing (not reconstructing) and saving certain types of torn ACL’s.

For more information on ACL tears in female athletes, or concerns about knee health, contact Dr. Cunningham today. Vail, CO office at (970) 476-2451, or in Frisco, CO (970) 668-3633.