To screen immune infiltration related genes in osteoarthritis (OA), multiple microarray data were obtained from Gene Expression Omnibus (GEO) database, and divided into a training set and a validation set to screen out the differentially expressed genes (DEGs). Then all genes in the training set were analyzed using Gene Set Enrichment Analysis (GSEA) software for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Subsequently, GO and KEGG analyses of DEGs were performed, and a pro-tein-protein interaction (PPI) network of the DEGs was constructed to screen hub genes. The validation set was used for differential validation of hub genes and determination of their diagnostic value. The content and proportion of 28 immune cells in the OA samples were obtained using the single sample gene set enrichment analysis (ssGSEA) algorithm, and the correlation between key gene expression and immune cell infiltration was calculated by Spearman’s correlation analysis. There were 27 DEGs found between the OA and normal car-tilage tissues. The GSEA results showed that gene expression changes in the OA samples were mainly in-volved in the processes such as humoral immune responses and histidine metabolic signaling pathways. GO and KEGG analyses of DEGs showed that the DEGs were associated with signaling pathways related to Staphylococcus aureus infection and NOD-like receptor signaling pathways. Four hub genes CAMP, S100A8, DEFA3, and COL5A2 were screened out from the DEGs, and their abnormal expressions in the OA tissues and high diagnostic value were confirmed. Further analysis of immune cell infiltration showed that obvious changes occurred in activated B cells and other immune cells in the OA cartilage tissues, and the four hub genes were significantly correlated with immune infiltration. The results indicated that activated B cells and other immune cells play an important role in the occurrence and development of OA, and CAMP, S100A8, DEFA3, and COL5A2 are hub genes associated with immune infiltration, which are closely related to the occurrence and development of OA.