Aging or injury to the joints can lead to cartilage degeneration and osteoarthritis (OA), for which there are limited effective treatments. We found that expression of 15-hydroxy prostaglandin dehydrogenase (15-PGDH) is increased in the articular cartilage of aged or injured mice. Both systemic and local inhibition of 15-PGDH with a small molecule inhibitor (PGDHi) led to regeneration of articular cartilage and reduction in OA-associated pain. Using single cell RNA-sequencing and multiplexed immunofluorescence imaging of cartilage, we identified the major chondrocyte subpopulations. Inhibition of 15-PGDH decreased hypertrophic-like chondrocytes expressing 15-PGDH and increased extracellular matrix-synthesizing articular chondrocytes. Cartilage regeneration appears to occur through gene expression changes in pre-existing chondrocytes, rather than stem or progenitor cell proliferation.