Objectives: After total knee arthroplasty (TKA), bone structure changes around prosthetics gradually appear. Adverse changes, such as decreased bone mineral density (BMD) and bone remodeling, can lead to joint loosening, affecting surgical outcomes. The study aims to detect BMD changes in the bone around the artificial knee early after TKA.

Methods: We performed a prospectively descriptive study on 54 patients who were operated at Viet Duc University Hospital from 4/2017 to 4/2019. Bone density was measured using dual-energy X-ray absorptiometry (DEXA) at the seventh days, 3,6,12, and 24 months post-surgery.

Results: The BMD in the medial metaphyseal region of interest decreased by 10.36 %, 11.5 %, 11.88 %, and 12.13 % at 3, 6, 12, and 24 months respectively, compared to 7 days post-surgery. The lateral metaphyseal region of interest decreased by 6.09 %, 6.47 %, 6.97 %, and 7.1 % and the tibial diaphyseal region of interest decreased by 3.75 %, 4.66 %, 5.91 %, and 5.8 % over the same follow-up periods. The BMD in the femoral condyle region of interest decreased by 8.15 %, 8.62 %, 9.24 %, and 10.65 % compared to the corresponding 7-day period at 3,6,12, and 24 months post-surgery.

Conclusion: The periprosthetic BMD rapidly reduced in the first 3 months, then gradually decreased. After 24 months of follow-up, the BMD in the medial metaphyseal region of interest decreased the most.