Job 3:12 - Exposition

Why did the knees prevent me? i.e. "Why did my mother take me on her knees and nurse me, instead of casting me on the ground, where I should have perished?" There seems to be an allusion to the practice of parents only bringing up a certain number of their children. Or why the breasts that I should suck? i.e. "Why were breasts offered to me, that I should suck them? How much better would it have been if I had been allowed to perish of inanition!"