Yo mama is so clumsy, when she had her first kickboxing lesson, she kicked herself in the testicles.
Clumsy Yo Mama
Explanation
Explain Bear
Hey, dummy! The joke is that yo mama is so clumsy that she ended up kicking herself in the nads during kickboxing. It's funny because chicks don't have balls, genius. And since you are reading this explanation, you must also be pretty clumsy.
SheSaidSheWas12
What testicles??????
Arik
That's part of the joke... Low brainer