An adapter assembly for operably connecting an end effector to a surgical instrument. The adapter assembly includes a first proximal shaft, a second proximal shaft, a first distal shaft, and a second distal shaft. The first proximal shaft includes a first gear assembly. The second proximal shaft defines a longitudinal axis and includes a second gear assembly. The first distal shaft is disposed along the longitudinal axis and includes a third gear assembly. The first gear assembly is mechanically engaged with the third gear assembly. The second distal shaft includes a fourth gear assembly. The second gear assembly is mechanically engaged with the fourth gear assembly. A distal portion of the second distal shaft is disposed at least partially within an internal cavity of the third gear assembly.