Osteoarthritis: Its Types and Clinical features

Osteoarthritis (OA) is also known as senile arthritis, degenerative or hypertrophic arthritis or osteoarthrosis.

It is very common joint disorder of elderly having symptoms of joint pain and stiffness. Osteoarthritis is a generative condition of joint cartilage with hypertrophic changes in the underlying bone. It mainly affects the weight bearing joints and is common in females.

According to WHO Osteoarthritis is the second commonest musculo skeletal problem and is an cimportant cause of disability in elderly.

Image showing Osteoarthritis in knees

Risk factors and Etiology:-

1. Age- Disease is more common in elderly people. The disease advances with the age.
2. Sex- Elderly female are more affected. Knee joint and Hand joint OA is common in Females while Hip joint OA is common in males.
3. Overweight or obesity- Obese person are more prone to develop OA.
4. Occupation- Overuse of particular joint has an increased risk of developing OA. Occupational knee bending is strongly associated with OA.
5. Joint Trauma- Trauma (injury) to joint and meniscectomy is an important risk factor in secondary OA.
6. Genetic- There is evidence of genetic basis of OA.
7. Chondrocalcinosis- It is a small risk factor for development of OA knee.
8. Mechanical stress- on joints and low grade inflammatory processes are believed to cause OA.

Types:

Osteoarthritis is classified into 2 types-

1. Primary OA

2. Secondary OA

Primary OA-

It occurs in elderly. It occurs due to degenerative changes in joints associated with ageing of tissues which the support the wear and tear concept. The exact cause of degeneration is not known but it is a slow process and arteriosclerosis and ischemia plays a major role. Repeated minor trauma, heredity, obesity, ageing all contributes to focal degenerative changes in articular cartilage of joints. 

Secondary OA-

It occurs at any age. Osteoarthritis developing at younger age is usually secondary. It develops due to wear and tear of joint due to any previous injury, fracture, congenital dislocation etc.

 Some diseases responsible for secondary OA are-

• Congenital joint disorders, dislocations etc.
• Inflammatory diseases
• Joint infection
• Obesity
• Injury to joint due to accident
• Diabetes

Pathogenesis and Pathological changes:

As osteoarthritis is a degenerative disorder, there is a gross loss of joint cartilage and damage of other joint tissues with hypertrophic changes in the underlying bone. Loss of cartilage is primary lesion and is formed by secondary bone formation.

Pathological Changes

Articular cartilage-

There is  degeneration of both cells and matrix, surface become rough. There is loss of condroitin sulphate from the ground substance of cartilage. Joints become vulnerable due to unsupported collagen fibril. As a result there is gradual loss of elasticity and the subcondral bones get exposed and no longer protected from the effect of weight and pressure on them.

Bones-

Bones of affected joints become highly polished called as ebernation. Bones get rarified, degenerated and new bone outgrowths in the form of "spurs" or osteophytes are formed on the margins of the joints. Heberden nodes or Bouchord’s nodesmay form on joints of fingers (smaller joints). These are hard bony enlargements. Spur or osteophytes are cartilaginous outgrowths at the joint margins which get ossified later.

Synovial membrane-

There is mild inflammation of synovial membrane. It becomes fibrous and fatty and gets change into cartilage, the broken pieces when detached into joint space they are called as "joint mice". There is synovial effusion associated with chronic synovitis.

Ligaments-

Ligaments of affected joints becomes thickened and fibrotic and the menisci are damaged.

Clinical Features-

Pain is the main cardinal feature associated with stiffness and diminished mobility of the affected joints.

• Pain- Generally localized sharp ache like or of burning sensation. Pain increases with physical activity or mechanical pressureon joint and relieved by rest. Pain may get worse in cold atmosphere(climatic condition).
• Stiffness- It is more prominent in morning while getting up from bed (lasts for 5-30 minutes).
• Crepitus- Crepitus or Crackling sound are produced on movement or while examining the affected joint.
• Muscle spasm and tendon contractions may experienced.
• Joint effusion- Joint may get filled with fluid. Joint effusion is common in OA of knees.
• Gait- As the large, weight bearing joints are usually affected, with the advancement of diseases the gait of pateint is generally affected.

Image showing Heberden’s node in finger joints

Diagnosis-

1. Clinical- Physical examination of joints.
2. Radiological
3. X-Ray- Joint space narrowing, osteophytes, sub chondral sclerosis are seen in X-Ray, subchondral cyst, deformities, loose bodies, calcification.

X-Ray knee joint AP and Lteral view showing changes

3. CT scan

4. MRI