There are few reports on bone mineral density (BMD) changes of axial bones after total knee replacement (TKR) due to severe osteoarthritis (OA) of the knee joint and its results are controversial. The purpose of our study was to measure the BMD changes of hip and spine in patients receiving TKR due to severe OA and to identify clinical factors relating BMD changes.

Among 66 female patients above 65 years old who underwent TKR due to severe OA and checked preoperative BMD, 52 patients who checked 1 year follow up BMD were enrolled. We investigated the association of the BMD changes with bilaterality of operation, obesity, preoperative knee functional scores, bisphosphonate medication, and diagnosis of osteoporosis.

We found no correlation between BMD changes and bilaterality of operation, obesity, preoperative knee functional scores and diagnosis of osteoporosis. Spine BMD increased in non-treatment and bisphosphonate treatment group but total hip BMD significantly increased in bisphosphonate treatment group.

Bisphosphonate treatment for 1 year prevents early reduction of hip BMD just after TKR regardless osteoporosis diagnosis. We considered that the bisphosphonate medication would be beneficial to prevention of later hip fracture in elderly patient receiving TKR due to severe OA of knee joints.