SAN DIEGO — Someday, perhaps, printers will revolutionize the world of medicine, churning out hearts, livers and other organs to ease transplantation shortages. For now, though, Darryl D’Lima would settle for a little bit of knee cartilage.

Dr. D’Lima, who heads an orthopedic research lab at the Scripps Clinic here, has already made bioartificial cartilage in cow tissue, modifying an old inkjet printer to put down layer after layer of a gel containing living cells. He has also printed cartilage in tissue removed from patients who have undergone knee replacement surgery.

There is much work to do to perfect the process, get regulatory approvals and conduct clinical trials, but his eventual goal sounds like something from science fiction: to have a printer in the operating room that could custom-print new cartilage directly in the body to repair or replace tissue that is missing because of injury or arthritis.

Just as 3-D printers have gained in popularity among hobbyists and companies who use them to create everyday objects, prototypes and spare parts (and even a crude gun), there has been a rise in interest in using similar technology in medicine. Instead of the plastics or powders used in conventional 3-D printers to build an object layer by layer, so-called bioprinters print cells, usually in a liquid or gel. The goal isn’t to create a widget or a toy, but to assemble living tissue.