A lead extension at least one lead extension body; terminals disposed along one end portion of the lead extension body(ies); a lead extension connector disposed along another end portion of the lead extension body(ies); and conductors electrically coupling the connector contacts in the lead extension connector to the terminals. The lead extension connector can include lead channels with non-straight paths to facilitate retention of leads. Alternatively, the lead extension connector can include one or more stretchable boots to each receive a lead when stretched and to grip the lead when relaxed. Alternatively, the lead extension connector can have two connector bodies with a pin channel and pin, respectively. When the pin is inserted into the pin channel, the pin compresses a portion of the connector body against the lead to retain the lead within the connector.