SINEW (sĭ'nū, Heb. gîdh, sinew). The tendons and sinews of the body (Job.40.17; Ezek.37.6-Ezek.37.9 kjv; niv “tendons”). The word is used also in a figurative sense (Isa.48.4).
SINEW (גִּיד, H1630). According to the Oxford English Dictionary the word “sinew” means tendon or nerve. A tendon is a tough fibrous band connecting muscle to bone, and this meaning fits most of the Biblical references well. Sinews are depicted as holding the bones of the body together (Job 10:11; 40:17; Ezek 37:6, 8). In the latter case the sinews were the first covering for the dry bones.
Jacob’s experience at Penuel (Gen 32) may have involved a mighty contraction of the muscle and tendon (“the sinew that shrank” [KJV] or contracted) that tore muscle fibers and left Jacob limping at dawn. “Out of joint” would refer to any injury of the hip region. Taken literally, it would imply a dislocation of the hip, a major injury making walking impossible.
International Standard Bible Encyclopedia (1915)
(gidh (Job 10:11, etc.)): The tendons and sinews of the body are uniformly (7 times) thus called. "Therefore the children of Israel eat not the sinew of the hip which is upon the hollow of the thigh, unto this day: because he touched the hollow of Jacob’s thigh in the sinew of the hip" (Ge 32:32). In the poetical description of Behemoth (hippopotamus) it is said: "He moveth his tail like a cedar: the sinews of his thighs are knit together" (Job 40:17). The prophet Ezekiel saw in his vision (37:6,8) that the dry bones were gathered together, that they were covered with sinews, flesh and skin, and that they were revived by the spirit of the Lord. In figurative language the neck of the obstinate is compared to an "iron sinew" (Isa 48:4). the "my sinews take no rest" (we`oreqay lo’ yishkabhun, Job 30:17) has been corrected by the (British and American) into "the pains that gnaw me take no rest," but the earlier version has been retained in the margin.