Case 69: Osteoarthritis

No clinical history is available for this case.

Macroscopic pathology

Microscopic pathology

Macroscopic examination of the slide shows a rectangular portion of tissue. The interwoven trabeculae of cortical bone can be clearly identified. The pale pink tissue along the upper surface of the tissue block represents the articular cartilage.

Under the microscope look first at the articular cartilage (1). The loss of proteoglycans results in decreased metachromasia (2) of the cartilage. This accounts for the eosinophilic as opposed to basophilic staining. The surface of the articular cartilage should be smooth; in this case fissuring, pitting and flaking (1), (2) are clearly seen. In some areas the articular cartilage has disappeared altogether exposing subchondral bone (2). This exposure of subchondral bone may lead to increased vascularity and thickening of the bony trabeculae (2). These changes are clearly seen in a number of areas on this slide. In other areas death of osteocytes or increased osteoclastic activity has led to thinning of the bony trabeculae with microcyst (1) formation. As a result of all these changes, deformation of the articular ends of the bone may occur.

Normal bone & soft tissue tissues

Click on any hyperlink text in the slide description above to take you to a microscopic view that illustrates the point. The picture will be resized to fill your screen. You can then enlarge the picture to full size by clicking anywhere within it. Or you can click on one of the pictures below for the same result. Press the left browser arrow to return here. Where there are numbers in brackets, these refer to the numbers of the pictures below.

Micro 1 of 2

Micro 2 of 2

Test yourself on the pictures of this case - Link to the bone and soft tissue test pictures

Commentary

Patients with osteoarthritis usually have stiffness and pain first thing in the morning which subsides once they start moving about but then recurs later in the day as the result of undue activity. The hips, knees and back are the joints most often involved.

Learning objectives

1. Recognise the key features of osteoarthritis (degenerative arthritis)
2. Understand how the pathological changes lead to the clinical state