what is special about fibro-cartillages?
they are resistant to wear and tear (withstand body weight for 70-80 years)
greater mobility comes with less stability vice versa
the hip bone fuses at 13-15 years of age, before the fusion it is made up of 3 separate bones known as the ilium, ischium and pubic

the highest point. of the iliac crest is L4
Pubic symphysis - secondary cartilaginous (fibrocartilage joint), supported by superior and arcuate ligaments.
Sacro-iliac joint - synovial anteriorly, fibrous posteriorly (very limited movement)
supported by the Anterior and Posterior sacro-iliac and interosseous ligaments (the interosseous ligaments are extremely strong, nut they loosen off in pregnancy)