CLOCK and osteoarthritis: Bmal1 is an essential core clock gene in TTFLs, the knockout of which disrupts rhythmic oscillation and abolishes the CLOCK-BMAL1 heterodimer’s transcriptional function.1,7–9 Circadian clock disruption is reportedly closely associated with many diseases, such as cancer, cardiovascular diseases, neurodegenerative disorders, liver and kidney dysfunction, and osteoarthritis.10–14 However, the role of the circadian clock in the development of intervertebral disc degeneration (IDD) is still unclear.