INTRODUCTION:
Osteoarthritis (OA) is a complex chronic illness that affects joints and causes substantial pain and impairment. It is the most common cause of disability worldwide and is characterized by articular cartilage (AC) degeneration with subchondral bone sclerosis, cyst formation, osteophyte formation, synovial lesions, and alterations in surrounding structures. Osteoarthritis mostly affects persons above the age of 50, with femalepredominance.

AIM OF THE WORK:
The aim of the present work was to study the anatomical and histopathological changes in a rat model of monosodium iodoacetate - induced osteoarthritis and to assess the possible therapeutic effects of intra-articular injection of bone marrow mesenchymal stem cell (BM-MSC) versus extracellular vesicles (EV) in a rat model of MIA induced OA.

SUBJECTS AND METHODS:
In this study we used Monosodium Iodoacetate (MIA) to induce knee osteoarthritis in rats. The current was carried out on 27albino rats. The rats were divided into two healthy male rats (weighing about 30 ± 5 g), to obtain the mesenchymal stem cells, and twenty-five female rats (weighing about 200 ± 20 g) which were considered as the experimental group. The experimental group was then divided into ten rats which served as the control group (group I) which were given free access to water and received a standard diet,