I have a muscle problem (Arthrogryposis Multiplex Congenita) that affects my legs so I cannot straighten them fully (maybe 95% straight) and I cannot kneel further than a sitting position. It's not a genetic thing. The most likely cause was that the muscles didn't develop fully because the womb I was timesharing in was too small to allow movement. Just like when people go into a coma and their limbs aren't exercised, the muscles can atrophy.
When I was 16 I had corrective surgery for scoliosis. Since they did a spinal fusion and clamped a steel bar to my spine, so I am a little stiff in the back too. This all makes me walk a little weird.
If you have questions about anything, even potentially embarrasing ones, all you have to do is ask and i'll give you an honest and direct reply. I'm pretty much open about every aspect of my life.