RISK FACTORS 

• Increasing Age
• Female Gender 
• Obesity 
• Joint Anatomic Factors
• Previous Joint injury
• Positive family history 
• Disease conditions like: Haemoglobinopathies, Diabetes mellitus, neuropathic disorders and bone disorders such as Paget disease or avascular necrosis 
• Previous surgical procedure

PATHOPHYSIOLOGY 

Osteoarthritis affects the entire tissues of the joint. The cause is usually due to interplay between the risk factors, abnormal joint mechanics and mechanical stress leading to the release of proinflammatory markers and proteases that eventually mediate the destruction of the joint.

The inflammation occurs as cytokines, metalloproteinases, PGE2, TNF alpha are released into the joint. These cause excessive matrix degradation is characteristic of the cartilage degeneration in osteoarthritis

In the early stage, there is increased synthesis of proteoglycans as an attempt by the chondrocytes to repair the cartilage damage. This results in swelling of cartilage as seen at this stage. This stage can last for years.

As the disease process continues, the cartilage becomes soften and loses its elasticity from the drop in the level of the proteoglycans. This further compromises the integrity of the joint surfaces.

With time, there is loss of joint space from the loss of cartilage. The cartilage damage progresses until there is exposure of the underlying bone. With continuous denudation of the articulating surfaces of the exposed bone, there is eburnation which can later progress to subchondral cyst and osteophyte formation. The pain seen in osteoarthritis can be due to vascular congestion of subchondral bone, synovitis, osteophytic periosteal elevation among others.

STAGES OF OSTEOARTHRITIS 

Stage 1: Proteolytic breakdown of the cartilage matrix 

Stage 2: Erosion and fibrillation of the surface of the cartilage occurs with further release of proteoglycan and collagen fragments into the synovial fluid.

Stage 3: Chronic inflammatory response in the synovium causes the breakdown of the products of cartilage.

CLINICAL PRESENTATION 

Patients with osteoarthritis may present with the following:

• Pain which is exacerbated by extensive use
• Stiffness usually following prolonged rest
• Swelling 
• Joint deformity 
• Joint instability 

On examination there can be:

• Malalignment with a bony enlargement
• Heberden nodes in the DIP joints of the hand
• Bouchard's nodes in the PIP joints of the hand 
• Tenderness at joint lines
• Effusion
• Crepitus
• Reduced range of movement 

INVESTIGATIONS 

The aim of investigating is to confirm diagnosis and rule out differentials. These include:

• Full blood count, erythrocyte sedimentation rate, rheumatoid factor, antinuclear antibodies. These are to rule out inflammatory arthritis.
• Plain x-ray: In load bearing areas like the knees, there can be loss of joint space, presence of osteophytes, subchondral cyst and subchondral sclerosis.
• Arthrocentesis can be done to exclude inflammatory arthritis, infection or crystal arthropathy.

TREATMENT 

Treatment can be subdivided into non-pharmacological and pharmacological measures.

NON-PHARMACOLOGICAL MEASURES

• Patient education on the nature of the disease.
• Heat and/or cold compress on the affected joint.
• Exercise such as strengthening quadriceps in osteoarthritis of the knee.
• Physical therapy.
• Occupational therapy for osteoarthritis affecting the hand bones. 
• Unloading the affected joints using walking aids like canes, crutches or a walker.

PHARMACOLOGICAL MEASURES 

• Analgesic and anti-inflammatory drugs: Depending on the extent of pain and the disease, one can begin with the use of paracetamol, topical non-steroidal anti-inflammatory drugs (NSAIDS), followed by oral NSAIDS, then opioids like codeine, morphine. Tramadol should be used restrictively because of high addiction risk and difficulty for patients to stop using it.
• A selective non-epinephrine reuptake inhibitor such as duloxetine can also be used for the pain, as has been shown to be effective.
• Intra-articular injection of corticosteroid or sodium hyaluronate or platelet rich plasma can also be administered.
• Additional measures include the use of muscle relaxants and glucosamine/chondroitin sulfate.

In extreme cases, surgery can be performed.

• Osteotomy for those with mal-aligned joints who want to continue activity.
• Arthroplasty: surgical removal of joint surface and insertion of a prosthesis.

CONCLUSION 

Osteoarthritis is the most common joint disorder. Patients should be well educated in this condition and be well managed to improve their quality of life.