Therefore to this day the Israelites do not eat the tendon attached to the socket of the hip, because the socket of Jacob’s hip was struck near that tendon.
We have here the remarkable story of Jacob's wrestling with the angel and prevailing, which is referred to, Hos 12:4. Very early in the morning, a great while before day, Jacob had helped his wives and his children over the river, and he desired to be private, and was left alone, that he might again more fully spread his cares and fears before God in prayer.
Commenting on Genesis 32:24-32
Therefore the children of Israel eat not of the sinew which shrank,.... Which was contracted by the touch of the angel, and by which it was weakened and benumbed; or the sinew of the part that was out of joint, the sinew or tendon that keeps the thigh bone in the socket, together with the flesh that covered it, or the muscle in which it...
the sinew which shrank--the nerve that fastens the thigh bone in its socket. The practice of the Jews in abstaining from eating this in the flesh of animals, is not founded on the law of Moses, but is merely a traditional usage. The sinew is carefully extracted; and where there are no persons skilled enough for that operation, they do not make use of the hind legs at all.