WordNet sense 1 (used of old persons or old trees; covered with knobs or knots):

gnarled, gnarly, knobbed, knotted

WordNet sense 2 (having or marked by bends or angles; not straight or aligned):

crooked, crooked

WordNet sense 3 (highly complex or intricate):

byzantine, convoluted, involved, tortuous

WordNet sense 4 (complicated in structure; consisting of interconnected parts):

complex, complex

WordNet sense 5 (making great mental demands; hard to comprehend or solve or believe):

baffling, problematic, problematical, tough

WordNet sense 6 (not easy; requiring great physical or mental effort to accomplish or comprehend or endure):

difficult, hard

WordNet sense 7 (tangled in knots or snarls):

snarly, snarled

WordNet sense 8 (in a confused mass):

tangled