**5.2 Clinical features**

212 Biomedical Science, Engineering and Technology

• *Role of inflammatory mediators:* Mediators such as TNF-α and IL-1 stimulate MMPs

• *Tissue inhibitors of MMPs:* Tissue inhibitors of MMPs regulate the MMPs. Therefore any disturbance of this regulatory mechanism may lead to increased cartilage degradation

• *Growth factors deficiency:* Growth factors such as insulin-like growth factor and transforming growth factor enhance collagen synthesis and so when these factors are

secretion and this inhibit collagen production.

and may contribute to the development of OA.

deficient matrix repair is impaired.

Fig. 2. Different factors that influence OA process.

Table 1. Stages of OA (Martel-Pelletier, 2004)

**5.1 Classification of OA** 

**Primary OA** 

**Secondary OA** 

**Stage I** There is proteolytic breakdown of cartilage matrix

**Stage II** There is fibrillation and erosion of cartilage surface, accompanied by the release

**Stage III** Synovial inflammation begins when synovial cells ingest a breakdown product

of breakdown products into the synovial fluid

through phagocytosisand produce proteases and proinflammatory cytokines

Has no known cause. Common. Related to aging and hereditary. May be localised or generalised. Commonly affects the distal interphalangeal joints of the hands, hip and the knee. The cervical and lumbar spine may be affected.

Causes include articular injury, obesity, Paget's disease, or inflammatory arthritis and aging process. May be localised or generalised. May affect any joint and can occur at any age.

• Genetic susceptibility

Pain and functional restriction are the main symptoms in OA. The pain is characteristically made worse by movement and relieved by rest.


Fig. 3. Radiological changes in Osteoarthritis of the knees. (A) AP view of the left knee shows medial joint space narrowing (arrow). (B) Lateral view shows sclerosis with marked osteophyte formation (arrows). (C) Medial joint space narrowing (white arrow) causing a varus deformity of the knee and collapse of the joint space with destruction of the medial cartilage and the subchondral cortex (open arrow heads). (D) Subchondral cysts are noted (solid arrow head).
