We all know that females and males have inherent physiological and anatomical differences. In the following paragraphs, we will take a look at several of these differences that we know contribute to a greater number and more frequent occurrence of certain pathokinematic movement patterns in females, and consequently a greater number of certain kinds of lower extremity injuries. Let’s begin by looking at the most obvious group of differences between males and females, namely those related to body structure and posture. These include obvious differences in skeletal make-up, peak height, body composition, muscle tissue, and the not so obvious circulatory and cardiorespiratory capacity differences[ii]. We will also review other differences in males and females that may serve to further explain the increased frequency and types of pathokinematics we see in women including those related to biomechanics, neuromuscular function, kinesthetia or proprioception, hormones, and core (including the hip) strength.
This increased width facilitates pregnancy and childbirth. However, the wider pelvis in females alters the position of the femur and adds to increased Q-angles at the knee where the tibia and femur articulate. The Q-angle, or quadriceps angle, is formed in the frontal plane by two line segments: one that is drawn from the tibial tubercle of the middle of the patella, and another drawn from the middle of the patella to the ASIS, or the anterior superior iliac spine. The Q-angle in normal males as determined in a study of 75 males and females was 14 degrees (+/- 3) for males and 17 degrees (+/- 3) in females.[iii] While it has been speculated that the female Q-angle can contribute to ACL loading by positioning the knee in valgus (knock knee position) and thereby place additional stress on the ACL in this population, this supposition has not been supported by any experimental data as of this writing.[iv]
We also know that females have a smaller femoral notch than males when we look at male and female anatomy in comparison[v]. In looking at female pathokinematics and the likelihood of ACL injury, we can see why this might be an important structural difference between the two sexes. The ACL originates at the posterior portion of the intercondylar notch of the femur. It is speculated that a decreased notch space can lead to increased stress or wearing on structures of the knee, namely the ACL, most notably during twisting and cutting motions. It is thought that a decreased notch space coupled with excessive hip or knee rotation could result in excessive loading of the ligament and thereby increase the wear and tear of the ligament and possibility of rupture.
These anatomical differences in pelvic anatomy between males and females may also contribute to increased weakness of the gluteus medius, lower abdominals and the transverse abdominus in females. All of these can contribute to less neuromuscular control of the core and hip which is so critical for controlling motion in the lower extremity. We will discuss this in more detail in later sections of this chapter.
Finally, females tend to achieve peak bone density at approximately 28.3 to 29.5 years of age (Recker, et al, JAMA 92)[vi]. Over time and with age, both male and female bones naturally deteriorate. There are factors that positively influence this like calcium supplementation as well as resistance exercise. Studies indicate that there is a biopositive adaptation process that occurs in the bones with resistance exercise and with sports (Krahl, et al. AJSM 94)[vii] and this adaptation can lead to higher peak bone densities than would occur without exercise. However there is a gender difference with female bone loss occurring at an accelerated rate in comparison to males. This tends to occur during the ages of 45-55 years of age and can lead to an increased risk and likelihood of fracture with increasing age. Additionally, females are much more likely to suffer from osteoporosis (disease in which bones become more porous due to a reduction in bone mineral density). In some instances, this reduction in bone mineral density is exacerbated by the effects of estrogen deficiency that occurs following menopause, as well as several other factors common to females. Fractures in situations such as falls that would not have occurred in healthy adults with normal bone density are the primary risk in individuals with osteoporosis. Full weight bearing exercise as well as strength training are effective preventative strategies to manage and even reverse bone loss associated with osteoporosis. Consequently, females benefit greatly from incorporating weight bearing and strength training exercises into their training programs early in life to aid in development and maintain more optimal bone density later in life.
Next week we will continue to investigate the impact skeletal maturity has on pathokinematics. Stay tuned and share the passion. #ACL #Prevention @PhysioCorp