The knees are often referred to in Scripture as the place where weakness of the body, from whatever cause, readily manifests itself: e.g. from terror (Job 4:4; Da 5:8), or fasting (Ps 109:24). The reference in De 28:35 seems to be to 'joint leprosy,' in which, after the toes and fingers, the joints of the larger limbs are attacked (Driver, Deut. in loc.). The laying of children on the knees of father or grandfather seems to have involved recognition of them as legitimate members of the family (Ge 30:8; 50:23). In many passages of Scripture kneeling is spoken of as the attitude assumed in prayer (1Ki 8:54; Ps 95:8; Da 6:10; Ac 20:36 etc.). To 'bow the knee' is equivalent to 'worship' (1Ki 19:18; Isa 45:23; Ro 14:11 etc.). To fall upon the knees before a superior is an act at once of reverence and of entreaty (2Ki 1:13; Mt 17:14; Lu 5:8 etc.). In the court of an Eastern judge the writer has often seen men prostrate themselves, and then make their plea, resting upon their knees.

W. Ewing.