(image from Medline Plus)
Apparently female athletes have a really high incidence of knee injuries - particularly to the anterior cruciate ligament (ACL). That is a real footballer's injury. I'm showing my age and nationality now, but I always remember that as the injury that Paul (Gazza) Gascoigne suffered in the FA cup final in 1991.
Mike Boyle in a provocative article says that most women shouldn't run: wider hips mean narrower knees which leads to more injuries for the average female runner. Incidentally there is an interesting response to Boyle here.
Eric Cressey prescribes "increasing glute and hamstrings strength and optimizing frontal plane stability is crucial for resisting knock-knee tendencies and preventing ACL tears".
While I am sure that strengthening these muscles and structures will help, an article has just been published that indicates that the issue is about more than simple biomechanics. There is a problem here in terms of pathology - it is about the very nature of women's tendon strength. Perhaps while training can help, women are always going to suffer more soft tissue injuries than men.
The adaptability of tendon to loading differs in men and women.
Peter Magnusson S, Hansen M, Langberg H, Miller B, Haraldsson B, Kjoeller Westh E, Koskinen S, Aagaard P, Kjær M.
Institute of Sports Medicine Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark.
The reason why women sustain more soft tissue injury than men during physical activity is unknown. Connective tissue properties and extracellular matrix adaptability in human tendon were investigated in models that addressed biochemical, physiological and biomechanical aspects of tendon connective tissue in response to mechanical loading. Habitual training resulted in a larger patellar tendon in men but not in women. Following an acute bout of exercise, men had an elevated tendon collagen synthesis rate and this effect was less pronounced or absent in women. Moreover, levels of circulating oestrogen affected the acute exercise-related increase in collagen synthesis. Finally, the mechanical strength of isolated tendon collagen fascicles in men surpassed that of women. Thus, compared to men, women have (i) an attenuated tendon hypertrophy response to habitual training; (ii) a lower tendon collagen synthesis rate following acute exercise; (iii) a rate of tendon collagen synthesis which is further attenuated with elevated estradiol levels; and (iv) a lower mechanical strength of their tendons. These data indicate that tendons in women have a lower rate of new connective tissue formation, respond less to mechanical loading, and have a lower mechanical strength, which may leave the tissue more susceptible to injury.