Objective To explore the effects of focused low-intensity pulsed ultrasound (FLIPUS) on the expression of inflammatory cytokines and pyroptosis-related proteins in mouse knee joint chondrocyte injury induced by lipopolysaccharide (LPS) and the mechanism of chondroprotection. Methods Primary chondrocytes were isolated from knee cartilage of C57BL/6J mice and stimulated with LPS for 12 h to mimic osteoarthritic chondrocyte injury in vitro. The chondrocytes were divided into control group (only cultured in medium containing 10% FBS without any treatment), LPS group (LPS treatment for 12 h), and LPS+FLIPUS group (LPS treatment for 12 h followed by FLIPUS intervention for 20 min). The expression of collagen Ⅱ α1 (COL2α1), inflammatory cytokines (interleukin[IL]-18 and IL-1β), pyroptosis-related proteins (nucleotide-binding oligomerization domain-like receptor 3 [NLRP3], cleaved cysteine aspartic acid specific protease 1 (caspase 1), and N-terminal fragment of gasdermin D[GSDMD-N]), and cartilage matrix degradation factors (matrix metalloproteinase [MMP] 13, MMP3, and a disintegrin and metalloproteinase with thrombospondin 5[ADAMTS5]) were detected by Western blotting. The viability of chondrocytes was detected by calcein acetoxymethyl ester/propidium iodide (calcein AM/PI) fluorescent staining and lactate dehydrogenase (LDH) release assay, the morphology of chondrocytes was observed by scanning electron microscopy, and the levels of IL-1β and IL-18 in cell supernatant were detected by enzyme-linked immunosorbent assay. Results The primary chondrocytes were isolated from knee cartilage of the mice and osteoarthritic chondrocyte injury in vitro were successfully simulated. Compared with the control group, the expression of COL2α1 was significantly decreased in the LPS group (P<0.01), while the expression levels of MMP13, MMP3, ADAMTS5, NLRP3, GSDMD-N, cleaved caspase 1, IL-18, and IL-1β were significantly increased (all P<0.01); the levels of IL-18, IL-1β, and LDH in the cell supernatant were significantly increased (all P<0.01), with cell swelling and deformation, more pores on the membrane, loss of integrity, and increased cell mortality (P<0.01). Compared with the LPS group, the expression of COL2α1 was significantly increased in the knee chondrocytes of mice in the LPS+FLIPUS group (P<0.01), while the expression levels of MMP13, MMP3, ADAMTS5, NLRP3, GSDMD-N, cleaved caspase 1, IL-18, and IL-1β were significantly decreased (P<0.05, P<0.01); the levels of IL-18, IL-1β, and LDH in the cell supernatant were significantly decreased (P<0.05, P<0.01), with relieved cell swelling and membrane pores and decreased cell mortality (P<0.05). Conclusion FLIPUS may reduce chondrocytes injury induced by LPS in mice via inhibiting the expression of inflammatory cytokines and pyroptosis-related proteins.