An interesting challenge for colloid chemists is to design injectable materials that enable the minimally-invasive repair of damaged, load-bearing tissue. A key criterion for these materials is that they must be able to support biomechanical loads. Degeneration of the intervertebral disc (IVD) is a major cause of chronic low back pain. Microgel particles are cross-linked polymer colloid particles that swell in a good solvent. We hypothesised that a concentrated dispersion of pH-responsive microgel particles that contained high carboxylic acid concentrations would give an injectable fluid at low pH that would change to a gel at body pH capable of supporting loads similar to those experienced by IVD tissue in the body. In this work model pH-responsive poly(EA/MAA/BDDA) (ethylacrylate, methacrylic acid and butanediol diacrylate) microgel dispersions were used to investigated this hypothesis. The pH-triggered swelling of the particles was investigated using photon correlation spectroscopy and rheology. Strong pH-triggered particle swelling and fluid-to-gel transitions of the microgel dispersions occurred at pH values greater than 6.0 (Fig. 1a). The fluid-to-gel transition was also triggered within IVDs after injection of the microgel into model degenerated spinal units (Fig. 1b). Uniaxial compression data for degenerated IVDs containing injected microgel dispersions showed that pH-induced particle swelling restores the mechanical properties of the IVDs to normal (non-degenerated) values. This work demonstrates a new general approach that has long-term potential to restore the mechanical properties of damaged load-bearing tissue.