PS

*psḥ/ḫ - to be lame; have a dislocated limb (SED I No. 54ᵥ; HALOT 947)

Akkadian
pessû - lame, crippled (CAD P 327, AHw. 856)
Hebrew
psḥ - to be lame, limp (HALOT 947)
Hebrew
pissēaḥ - limping (HALOT 948)
Jewish Palestinian Aramaic
psḥ - to leap over (DJPA 439)
May be related.
Arabic
fsḫ - to dislocate, to remove from its place, to separate, to disperse; to be weak in intellect and in body (BK 2 592, Lane 2395)
Alternatively, may go back to PWS *pṣḥ ‘to smash, to grind’ or PWS *pšḫ ‘to break off, to separate’.
Arabic
fšḫ - II. avoir les membres du corps lâches, sans vigeur (to have loose body members, without vigor) (BK 2 592)
Related as a variant root with š vs. s and a meaning shift?
Ennemor
fušä - boil at the joint of the two parts of body (EDG 247)
May be related.