I had surgery on my jaw and it comes out of joint quite often now.
My jaw often slips out of joint because I had surgery on it.
ーI had surgery on my jaw and it comes out of joint quite often now.
「顎の手術をしたのでよく顎が外れる。」
I had surgery on ... で「…の手術をした」
jaw で「顎」
it comes out of joint で「（顎が）関節から外れる」
ーMy jaw often slips out of joint because I had surgery on it.
「手術をしたので顎が関節からよく外れる。」
My jaw slips out of joint で「顎が関節から外れる」とも言えます。
joint で「関節」
ご参考まで！
I had an operation on my jaw joint so my jaw often becomes loose.
I had surgery on my jaw joint so my jaw often goes out of joint.
顎の関節 は jaw joint と表現して良いと思います。
手術をした は I had an operation と言う表現を使うと良いです。
I had surgery と言うのも有。
この場合のよくはずれるは緩くなるような感覚に近いと思うので
often becomes loose と表現するのが良いかもしれません。
顎が間接からずれると言った感じで後者の
my jaw often goes out of joint とも表現できます。
カナダ 
日本 
