Hebrew

bäräk - knee (HALOT 160)

bäräk (< *bark-­; suff. birk-­). Note Hbr. pB. bōräk ‘knee-shaped shaft of a plough’ [ibid.].

PS
*bi/ark- - knee (SED I No. 39)
Cf. *rVk(u)b(­at)­ ‘knee’ (No. 232) and discussion in [GD 163], where separation of these two roots is also favored.