Abstract: BACKGROUND: Currently, treatment method for knee osteoarthritis includes oral medicine, joint cavity drug injection, and physiotherapy, but the curative effect is limited. Existing studies have confirmed that silicon-based bioceramics can promote cartilage and subchondral bone repair and vascular regeneration.
OBJECTIVE: To explore the effect of different concentrations of silicon-based bioceramics injected into the knee joint cavity in the treatment of knee osteoarthritis in rats. 
METHODS: Silicon-based bioceramics-calcium silicate was prepared. Twenty-five SD rats were randomly divided into five groups, with five rats in each group. The healthy group did not receive any intervention, and the modeling group, low-dose calcium silicate group, high-dose calcium silicate group, and saline group used anterior cruciate ligament transection to establish bilateral knee osteoarthritis models. Four weeks after modeling, 0.05 mL of 50 and 100 mg/mL calcium silicate solution were injected into the knee joint cavity in the low-dose calcium silicate group and high-dose calcium silicate group, respectively, and 0.05 mL of saline was injected into the knee joint cavity in the saline group, once a week for 4 consecutive weeks. In the fifth week of administration, bilateral knee joint Micro-CT detection, knee joint cartilage hematoxylin-eosin staining, and modified Mankin score were performed.
RESULTS AND CONCLUSION: R(1) Micro-CT quantitative analysis showed that compared with the healthy group, the volume fraction and number of trabeculae of the medial tibial plateau in the modeling group decreased (P < 0.05), and the separation of trabeculae increased (P < 0.05). Compared with the modeling group, the volume fraction and number of trabeculae of the medial tibial plateau in the low-dose calcium silicate group and the saline group increased (P < 0.05), and the separation of trabeculae decreased (P < 0.05). (2) Hematoxylin-eosin staining showed that the cartilage surface of the healthy group and the low-dose calcium silicate group was relatively smooth and flat, the chondrocytes were evenly distributed, without clustered chondrocytes, the tide line was complete, and the staining was uniform; the cartilage surface of the high-dose calcium silicate group was slightly uneven, the middle and deep cells were disordered, with a small number of clustered chondrocytes, the tide line was discontinuous, and the staining was uneven; the cartilage surface of the saline group and the modeling group was obviously rough, the cells were disordered, with a large number of clustered chondrocytes, the tide line disappeared, and the staining was uneven. The modified Mankin score of the healthy group was lower than that of the high-dose calcium silicate group, the saline group, and the modeling group (P < 0.05). The modified Mankin score of the high-dose calcium silicate group and the low-dose calcium silicate group was lower than that of the saline group and the modeling group (P < 0.05). (3) The results show that calcium silicate knee joint injection has a certain effect in the treatment of knee osteoarthritis. Compared with 100 mg/mL calcium silicate solution, 50 mg/mL calcium silicate solution can promote the recovery of subchondral bone and cartilage.

Key words: knee osteoarthritis, silicon-based bioceramics, calcium silicate, knee joint injection, saline, Micro-CT, Mankin score, engineered bone material