Consider a closed $3$-manifold $M$ and a knot $K$ in $M$. Is it necessarily true that $\pi_2 (M \setminus K) = 0$? If not, are there any conditions on $M$ and/or $K$ to ensure the above 2nd homotopy group of the knot complement is trivial? Thanks! (Note: This is, of course, true when $M$ is simply connected --> $S^3$)