A system comprises a medical instrument including a rotatable capstan. The rotatable capstan includes a first coupling feature and a drive system including a rotatable drive element. The rotatable drive element includes a second coupling feature. The first and second coupling features have an aligned engagement configuration in which rotation of the rotatable drive element induces rotation of the rotatable capstan and a non-aligned engagement configuration in which rotation of the rotatable drive element does not induce rotation of the rotatable capstan.