Osteoarthritis (OA) is a degenerative joint disease. Causes is multifactorial, and still not understood. Commonly it is thought to be wear and tear of joints as one ages.
Two types of Osteoarthritis are recognised –
primary and secondary.
Primary OA: This occurs in a joint de novo. It occurs in old age, mainly in the weight bearing joints (knee and hip).
In a generalised variety, the trapezio-metacarpal joint of the thumb and the distal inter-phalangeal joints of the fingers are also affected. Primary OA is commoner than secondary OA.
Secondary OA: In this type, there is an underlying primary disease of the joint which leads to degeneration of the joint, often many years later.
It may occur at any age after adolescence, and occurs commonly at the hip. Predisposing factors are:
(i) congenital mal development of a joint;
(ii) irregularity of the joint surfaces from previous trauma
(iii) previous disease producing a damaged articular surface
(iv) internal derangement of the knee, such as a loose body
(v) mal-alignment (bow legs etc.)
(vi) obesity and excessive weight.
Causes of secondary Osteoarthritis of the hip
Avascular necrosis
Idiopathic
Post-traumatic e.g., fracture of femoral neck Alcoholism
Post-partum osteonecrosis
Chronic liver failure
Patient on steroids
Patient on dialysis
Sickle cell anaemia
Coxa vara
Congenital dislocation of hip (CDH)
Old septic arthritis of the hip
Malunited fractures
Fractures of the acetabulum
PATHOLOGY
Osteoarthritis is a degenerative condition primarily affecting the articular cartilage. The first change observed is an increase in water content and depletion of the proteoglycans from the cartilage matrix. Repeated weight bearing on such a cartilage leads to its fibrillation.
The cartilage gets abraded by the grinding mechanism at work at the points of contact between the apposing articular surfaces, until eventually the underlying bone is exposed. With further ‘rubbing’, the subchondral bone becomes hard and glossy.
Meanwhile, the bone at the margins of the joint hypertrophies to form a rim of projecting spurs known as osteophytes. A similar mechanism results in the formation of subchondral cysts and sclerosis.
The loose flakes of cartilage incite synovial inflammation and thickening of the capsule, leading to deformity and stiffness of the joint. Often one compartment of a joint is affected more than the other.
For example, in the knee joint, the medial compartment is affected more than the lateral, leading to a varus deformity (genu varum).
CLINICAL FEATURES OSTEOARTHRITIS
The disease occurs in elderly people, mostly in the major joints of the lower limb, frequently bilaterally. There is a geographical variation in the joints involved, depending probably upon the daily activities of a population.
The hip joint is commonly affected in a popula habits, while the knee is involved more commonly in a population with Asian living habits i.e., the habit of squatting and sitting cross legged.
Pain is the earliest symptom. It occurs inter mittently in the beginning, but becomes constant over months or years. Initially, it is dull pain and comes on starting an activity after a period of rest; but later it becomes worse and cramp-like, and comes after activity.
A coarse crepitus may be complained of by some patients. Swelling of the joint is usually a late feature, and is due to the effusion caused by inflammation of the synovial tissues.
Stiffness is initially due to pain and muscle spasm; but later, capsular contracture and incon gruity of the joint surface contribute to it. Other symptoms are: a feeling of ‘instability’ of the joint, and ‘locking’ resulting from loose bodies and frayed menisci.
EXAMINATION
Following findings may be present:
Tenderness on the joint line
Crepitus on moving the joint
Irregular and enlarged-looking joint due to
formation of peripheral osteophytes • Deformity -varus of the knee, flexion-adduction external rotation of the hip
Effusion – rare and transient
Terminal limitation of joint movement
Subluxation detected on ligament testing Wasting of quadriceps femoris muscle.
Investigations
Radiological examination: The diagnosis of osteoarthritis is mainly radiological. The following are some of the radiological features:
Narrowing of joint space, often limited to a part of the joint e.g., may be limited to medial compartment of tibio-femoral joint of the knee.
Subchondral sclerosis – dense bone under the articular surface
Subchondral cysts
Osteophyte formation
Loose bodies
Deformity of the joint
Other investigations are made primarily to detect an underlying cause. These consist of the following:
Serological tests and ESR to rule out rheumatoid arthritis.
Serum uric acid to rule out gout
Arthroscopy, if a loose body or frayed meniscus is suspected
TREATMENT OF OSTEOARTHRITIS
Principles of treatment: Once the disease starts, it progresses gradually, and there is no way to stop it. Hence efforts are directed, wherever possible, to the following:
a) To delay the occurrence of the disease, if the disease has not begun yet.
b) To stall progress of the disease and relieve symptoms, if the disease is in early stages.
c) To rehabilitate the patient, with or without surgery, if his disabilities can be partially or completely alleviated.
Methods of treatment: To achieve the above objectives, the following therapeutic measures may be undertaken:
a) Drugs: Analgesics are used mainly to suppress pain. A trial of different drugs is carried out to find a suitable drug for a particular patient. Long-acting formulations are preferred.
b) Chondroprotective agents: Agents such as Glucosamine and Chondroitin sulphate have been introduced, claiming to be the agents which result in repair of the damaged cartilage. Their role as disease modifying agents has yet not been established, but these could be tried in some early cases.
Viscosuplementation: Sodium Hylarunon has been introduced. It is injected in the joint 3-5 times at weekly interval. It is supposed to improve cartilage functions, and is claimed to be chondroprotective.
d) Supportive therapy: This is a useful and harmless method of treatment and often gives gratifying results. It consists of the following: Weight reduction, in an obese patient.
Avoidance of stress and strain to the affected joint in day-to-day activities. For example, a patient with OA of the knee is advised to avoid standing or running whenever possible. Sitting cross legged and squatting is harmful for OA of the knee.
Local heat provides relief of pain and stiffness.
Exercises for building up the muscles controlling the joint help in providing stability to the joint.
The local application of counter-irritants and liniments sometimes provide dramatic relief.
e) Surgical treatment: In selected cases, surgery can provide significant relief. Following are some of the surgical procedures performed for OA:
OSTEOTOMY: Osteotomy near a joint has been known to bring about relief in symptoms, especially in arthritic joints with deformities. A high tibial osteotomy for OA of the knee with genu varum and inter-trochanteric osteotomy for OA of the hip have been shown to be useful for pain relief.
JOINT REPLACEMENT: For cases crippled with advanced damage to the joint, total joint replacement operation has provided remarkable rehabilitation. These are now commonly performed for the hip and knee. An artificial joint serves for about 10-15 years.
JOINT DEBRIDEMENT: This operation is not so popular now. In this, the affected joint is opened, degenerated cartilage smoothened, and osteophytes and the hypertrophied synovium excised. The results are unpredictable.
ARTHROSCOPIC PROCEDURES: Arthroscopic removal of loose bodies, degenerated meniscal tears and other such procedures have become popular because of their less invasive nature.
In arthroscopic chondro plasty, the degenerated, fibrillated cartilage is excised using a power-driven shaver under arthroscopic vision. Results are unpredictable.
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