knotty - adjective

• making great mental demands; hard to comprehend or solve or believe
• used of old persons or old trees; covered with knobs or knots
• highly complex or intricate and occasionally devious
• tangled in knots or snarls

knotty - thesaurus

baffling   byzantine   convoluted   elusive   gnarled   gnarly   involved   knobbed   knotted   problematic   problematical   snarled   snarly   tangled   tortuous   tough