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Case Reports in Orthopedics
Volume 2014, Article ID 514058, 6 pages
http://dx.doi.org/10.1155/2014/514058
Case Report

The Relationship between Osteoporosis and Osteoarthritis of the Knee: A Report of 2 Cases with Suspected Osteonecrosis

1South Akita Orthopedic Clinic, Seiwakai, 96-2 Kaidousita, Syowa-Ookubo, Katagami 018-1401, Japan
2Department of Orthopedic Surgery, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan

Received 26 February 2014; Accepted 27 May 2014; Published 17 June 2014

Academic Editor: John Nyland

Copyright © 2014 Akira Horikawa et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Knee specimens of two osteoporotic patients who underwent unilateral knee arthroplasty for suspected osteonecrosis of the knee were examined histologically. Preoperative findings of magnetic resonance images in both patients were consistent with the diagnosis of osteonecrosis of the medial femoral condyles, although plain X-rays showed minimal degenerative changes. In both patients, preoperative bone mineral densities of the femoral condyle and proximal tibia of the affected side were lower than those of the unaffected side. Pathological examination of the resected femoral condyle and proximal tibia showed almost intact joint cartilage, healing of the collapsed subchondral bone, and significant trabecular bone loss. Histologically, no evidence of osteonecrosis, including empty lacunae of the trabecular bone, was observed. These findings indicated that subchondral bone collapse caused by osteoporosis, but not osteonecrosis, initiated the osteoarthritic change of the affected knee. This report emphasizes that there may be cases of progressive local osteoarthritis caused by fracture of subchondral bone because of osteoporosis.