Calculating the probability that a cord makes a knot

Question

I use earphones to listen to music. The cord connected to the earphones often gets entangled in my pocket and makes a knot, which I always find hard to untangle.

How can I define and calculate the probability that my cord spontaneously makes a knot?

Thank you.

Answer 1

Upon request I post my comment as an answer:

There is an interesting article on this topic by Dorian M. Raymer and Douglas E. Smith:

Spontaneous knotting of an agitated string