I’m unclear as to the meaning of the word ירך that appears in Vayishlach, in 32:26. What’s the precise meaning of ירך often translated as hip, thigh, loin, gird etc. Which body part, bone or muscle is it? And what was Yaakov’s injury? P.s. Is there any spiritual, symbolic or figurative meaning to ירך?
Rashi (ibid) describes the verse as follows:
ויגע בכף ירכו. קוּלִית הַיָּרֵךְ הַתָּקוּעַ בְּקַּלְבּוּסִית קָרוּי כַּף, עַ"שֵׁ שֶׁהַבָּשָׂר שֶׁעָלֶיהָ כְּמִין כַּף שֶׁל קְדֵרָה:
ויגע בכף ירכו HE TOUCHED THE HOLLOW OF HIS THIGH — The upper thigh-bone that is sunk in the hip is called כף because the flesh on it (on this bone) has the form of the hollow part of a pot-ladle (כף).
So the יֶרֶךְ seems to be the femur - which was dislocated from the acetabulum, as Shadal explains.
The Medrash Shir HaShirim Rabbah 3:6 brings 3 opinions:
וַתֵּקַע כַּף יֶרֶךְ יַעֲקֹב, רַבִּי אֱלִיעֶזֶר וְרַבִּי בֶּרֶכְיָה, רַבִּי אֱלִיעֶזֶר אוֹמֵר שִׁיְּעָא, רַבִּי בֶּרֶכְיָה בְּשֵׁם רַבָסָא סִדְּקָהּ כְּדָג. רַבִּי נַחְמָן בַּר יַעֲקֹב אָמַר פֵּרְקָהּ מִמְּקוֹמָהּ, הֵיאַךְ מָה דְאַתְּ אָמַר (יחזקאל כג, יח): וַתֵּקַע נַפְשִׁי מֵעָלֶיהָ.
Rabbi Eliezer says he שִׁיְּעָא - (unclear what this word means. In the Targum of Ezekiel 13:12 it is used to mean coat or smear (a surface), so possibly he peeled it off? ), Rabbi Brechia says he split it open (the acetabulum, I assume) like a fish, while Rabbi Nachman bar Yaakov that he dislocated it (the femur, I assume.)
In later verses we see that it probably has something to do with the Sciatic nerve, as we don't eat the Sciatic nerve in commemoration of this incident.
Multiple commentators explain that - since the angel couldn't overcome him - he wanted to check if Yaakov was an angel, as angels don't have joints. By dislocating his hip, he proved he was human.
Others explain that he wanted to maim him so that he would be disqualified to do the Temple Services - the right he had purchased from Esav, The Ba'al Haturim brings both:
ויגע בכף ירכו לראות אם הוא מלאך כמותו אם היו לו קפיצים שהמלאכים אין להם קפיצים. א''נ לפוסלו מן העבודה לפי שקנה מעשו הבכורה שבהן העבודה: בכף ירכו בגימטריא לפוסלו מכהונה:
I recall he went for the hip to try prevent him from having more children; though I can't find any source for this and then it couldn't (medically) be the actual hip, but something else in the hip area.
Partial answer: In modern spoken Hebrew at least, the ירך is the part of your leg between the hip and the ankle. So, ירך means thigh. I think but am not certain that this is the only intended meaning as far back as the bible:
וַיַּךְ אוֹתָם שׁוֹק עַל-יָרֵךְ, מַכָּה גְדוֹלָה
Judges 15, verse 8. Translation (by me):
And he beat them thigh-over-calf, a great beating
I'm guessing perhaps you were thinking about the strange traslation this got in the King James bible:
And he smote them hip and thigh with a great slaughter
As for the spiritual part, someone more Jewish and spiritual than myself miight add to this answer. Remember, though, this particular mention regards the body-builder "spirituality" of Samson, a person who would whack people to death with the side of a Donkey's face; send foxes with burning tails to burn up Philistine villages' fields; and other such "spiritual" activities...