A novel injectable hydrogel that was synthesized by in situ crosslinking of hyaluronan and polyvinyl phosphonic acid was proposed in this study. Fourier transform infrared spectrum (FT-IR) analysis, scanning electron microscope (SEM), pH measurement, and biodegradation test were used to confirm its characteristics. The results permitted to prove successful crosslinking, observe the inner morphology of hydrogel and pore sizes distribution, and determine the decomposition of hydrogel components during incubation time. Result of pH measurement showed that the pH scale of hydrogel decreased when volume of PVPA increased. As a consequence, it affected the cytotoxicity value, cell proliferation, and cell growth behaviors of each hydrogel. Optical microscope observation showed that chondroblasts cell proliferated well on HA-PVPA hydrogel. Therefore, these results suggest that the new injectable hydrogel is appropriate for bone/cartilage regeneration applications.