Osteoarthritis is the main chronic bone disease of the elderly. At present, there is no treatment for osteoarthritis that can reverse the disease. The main research of this paper is to explore whether peripheral freehand monocytes can be used to control pain and restore motor function in patients with osteoarthritis. After the cells are purified by MOFI in a special medium, they are injected into the patient’s knee for a one-time joint injection. Experiments have found that isolated and purified mononuclear cells can effectively control inflammatory arthritis in animal models, and the performance is comparable to that of mesenchymal stem cells. A single-arm preliminary clinical trial showed that patients who received mononuclear cell injections had significant improvements in their pain index and degenerative arthritis index. In the treated population, the therapeutic effect can last up to 2 years. The preliminary results of this experiment show that the use of monocytes to treat degenerative arthritis is a novel treatment technique and a convenient solution.