The team also placed tight end Allen Reisner on IR, with the designation to return later in the season.
Lowery missed the last two games after sustaining a concussion on the first play at Seattle on Sept. 22. Joeckel (ankle) and Reisner (knee) were injured in Sunday's 34-20 loss at St. Louis.
The Jaguars (0-5) also were awarded offensive tackle Sam Young off waivers from Buffalo and promoted offensive tackle DeMarcus Love from the practice squad. They signed guard Jacques McClendon to the 53-man roster.
The team signed receiver Jeremy Ebert to the practice squad and waived receiver Tobais Palmer from the practice squad.