  We compute in many classes of examples the first potentially interesting
homotopy group of the space of embeddings of either an arc or a circle into a
manifold $M$ of dimension $d\geq4$. In particular, if $M$ is a simply connected
4-manifold the fundamental group of both of these embedding spaces is
isomorphic to the second homology group of $M$, answering a question posed by
Arone and Szymik. The case $d=3$ gives isotopy invariants of knots in a
3-manifold, that are universal of Vassiliev type $\leq1$, and reduce to
Schneiderman's concordance invariant.
