Lead assemblies with adjustable contacts

One aspect of the present disclosure relates to lead assemblies for stimulating tissue. The lead assemblies can include lead bodies that are slidably coupled to each other and include one or more contacts that are moveably disposed within the slits of the lead bodies. The positions of the one or more contacts can be adjusted to change the direction of stimulation. For example, the positions of the one or more contacts can be adjusted based on theoretically-optimal positions determined from a patient-specific computer model. Parameters of the stimulation applied by the one or more contacts can also be optimized based on the patient-specific computer model.