knotty

Short definition from Wiktionary

Adjective

1. 1
   Of string or something stringlike: full of, or tied up, in knots.
2. 2
   Of a part of the body, a tree, etc.: full of knots (knobs or swellings); gnarled, knobbly.
3. 3
   Complicated or tricky; complex, difficult.
4. 4
   Of an austere or hard nature; rugged.