Knee Injuries in Women | Looking at Hormones, Ligaments and Structure

By Kay Hartley | June 1, 2012 | 0 Comments

Hormones
Structure
Protecting Your Knees

Studies are showing that women are between 5 to 8 times more likely to suffer an anterior cruciate ligament (ACL) injury of the knee playing the same sport at the same level as a male. The reason this injury has been closely studied is that rupture of this ligament almost always results in a total knee reconstruction as it cannot repair itself. Other ligaments in the knee have limited capacity to heal albeit at a very slow rate.

I have chosen this example because research indicates that the frequency of women’s knee injuries is different to men’s for two reasons. Firstly, evidence indicates that hormone receptor sites to oestrogen and relaxin are found in this and other ligaments in the body. Secondly, women have different pelvic and lower limb development and anatomy to men.

Hormones

In regard to hormones, oestrogen and relaxin have been most closely studied.

Oestrogen

Oestrogen levels reach their peak during the follicular phase of the menstrual cycle just before ovulation and remain elevated until just before menstruation.

The effect of oestrogen on bone and ligaments include:

  • Inhibition of bone cells that breakdown bone (osteoclasts)
  • Inhibition of the development of new cells that breakdown bone
  • Promotes the survival of cells that build bone (osteoblasts)
  • Promotes the production of collagen in connective tissue including ligaments

Relaxin

Relaxin is produced during pregnancy; and in non-pregnant females during the luteal phase (2nd half) of the cycle. It peaks within 14 days of ovulation.

Effects of relaxin include:

  • Inhibition of collagen production
  • Promotes collagen breakdown

Taking into account the effect of these hormones, you might expect that women would be more vulnerable to injury pre-menstrually or at the beginning of the period when the ligaments would appear to be at their loosest. However, studies have shown inconclusive results. Some have shown a greater than expected percentage of injury mid cycle where you would expect the tissues to be at their stiffest and thickest. Yet others show statistically greater risk on day 1 or 2 of the cycle. So the research goes on and recent opinion suggests that there is no compelling evidence to alter training schedules in females in accordance with their menstrual cycles.

Structure

In order to give birth, women need a wider, rounder and more circular pelvic cavity and have smaller more forward facing hip joints. This results in an increase in the forward tilt of the pelvis and means the thigh bone (femur) is more turned and angled inwards. In turn, there is relatively (to a male) more stress on the inside of the knee.

Women report knee pain more commonly than men. At puberty, there are changes in the musculoskeletal system of both genders in terms of an increase in height and improved bone density. Additionally, lean muscle mass increases. Men lose body fat under the influence of testosterone while the hormonal changes women undergo leads to a gain in body fat. Effectively young women are weaker and heavier and have an increased body mass relative to young men. This discrepancy may be a factor in the higher injury rates amongst women as they may not be as effective in moving and stabilizing joints. At any time of life, any weakness in the core, hip and thigh muscles also increases risk of problems in women’s knees.

Protecting Your Knees

The presence of hormones and our basic skeletal structure are not easily changed, so the focus in on injury prevention. Knee injuries, for example, result after landing when jumping; sudden stops and starts; and rapid pivots - in other words, mostly for non-contact reasons. As such, areas such as muscle strength and training are under investigation. Factors including jumping technique, hamstring strength and balance can be addressed through training to protect a woman’s knees.

An example of this is that women tend to land after jumping with a much straighter knee. By learning to bend the knees slightly when landing, the load on the knee can be decreased by as much as 25 per cent. Strength training for core, pelvic, hip and thigh muscles can also aid with prevention.

Anecdotal evidence from trainers suggests that women in their 50’s returning to exercise seem to have an increased incidence of these injuries. Reasons for this could be lack of fitness in addition to the effects of diminishing oestrogen after menopause and its effect on the strength and resilience of connective tissue. The bottom line is post-menopausal women returning to exercise or any woman embarking on a new exercise regime would be advised to have a physical check and to obtain advice on exercises best suited to your fitness and stage of life.
 

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