Arthritis

12 September 2011

Osteoarthritis

Osteoarthritis is a disease that primarily affects the cartilage lining of the joints and the bones associated with the joints, the subchondral bones.

Alternative names

Degenerative joint disease / Spondylosis

Summary

  • Osteoarthritis (OA) is a disease affecting the cartilage and the lining of the bones of a joint.
  • It often arises as a result of wear and tear of joints.
  • Damage to the joints starts in the early 20s and 30s and joint changes are almost universal by the age of 70.
  • The main joints affected are those of the hands, neck, hips, knees and back.
  • Pain and stiffness of the joints are the main symptoms.
  • Treatment is primarily by exercise and weight loss, drugs playing only a small part in therapy.
  • The outcome is generally good if the person remains active and maintains a normal weight.
  • Symptom relief is possible with anti-inflammatory therapies called NSAIDs and COXIBs.
  • Glucosamine sulphate may provide pain and stiffness relief.
  • Severely damaged joints such as the hips and knees can be replaced very successfully.

Definition

Osteoarthritis is a disease that primarily affects the cartilage lining of the joints and the bones associated with the joints, the subchondral bones. However, all the tissues surrounding the affected joint eventually become abnormal. The cartilage lining the joint frays and outgrowths of bone form around the joint in an attempt at healing. Fragments of this bone break off and irritate the joints, which lose their natural lubrication and become stiff and noisy.

Causes

Osteoarthritis used to be seen as a result of wear and tear of the joints. In fact, the disease is now thought to have several subtypes, of which some are more aggressive and related to immune mechanisms, resulting in inflammation against self and an erosion of the cartilage and adjacent bone – called erosive osteoarthritis.

The mechanism is a complex system of interacting mechanical, biological, biochemical and enzymatic feedback loops. When one or more of these fail, osteoarthritis occurs. Anything that changes the microenvironment of the bone cell may initiate the chain of events, which lead to osteoarthritis – congenital joint abnormalities, genetic defects, infectious processes, metabolic processes and neurological disease. Trauma to a joint may initiate osteoarthritis, including prolonged overuse of a joint or group of joints.

Osteoarthritis has a large tendency to be a genetically primed disease, especially in the end joints of the fingers and the spine.

Who gets it and who is at risk?

Osteoarthritis is the most common of all disorders of the joints. The first symptoms appear usually in the 4th decade and 60-70% of people are affected by the 7th decade.

Early on, more women than men are affected, but this discrepancy is less marked in the elderly. There is a strong hereditary tendency, especially when hand joints are involved in women. There is evidence that genes coding for collagen components within cartilage may be abnormal, explaining the family clustering of this condition.

The earlier the onset and the greater the genetic factors, the greater the risks of developing OA are. Patients who have both parents affected will most certainly develop osteoarthritis.

Obesity is an independent risk factor for osteoarthritis of the knee, and may predict development of the condition 30 years later. Although mechanical loading is the obvious explanation for this link, other metabolic abnormalities associated with obesity may be at play.

Joint hypermobility is also an independent risk for the development of OA. Some patients may have extreme hypermobility, leading to recurrent stress injuries and early OA of weight bearing joints.

Symptoms and signs

The joints most commonly affected are the neck, hips, knees, back and small joints of the fingers. Initially osteoarthritis may be associated with an inflammatory process and the onset is seen with mild swelling and stiffness in the hands and affected joints. It is usually subtle and gradual. Pain is the earliest symptom, made worse by exercise. The stiffness is transient. Usually it is short lived in the morning (less than 30 minutes) and may recur after periods of sitting or inactivity. It usually improves with exercise.

As the disease progresses, the motion of the joints is decreased and the person may notice tenderness and grinding noises in the joint. The joint eventually enlarges from bony outgrowth. The bony enlargement is irreversible.

If the ligaments become lax, for example around the knee, the joint has increased instability with more pain. Tenderness to the touch and pain when the doctor moves the joint are signs of advanced disease. At this stage muscle spasm and contraction of the muscles around the joints add to the pain.

Osteoarthritis of the hip is characterized by increasing stiffness and loss of range of motion. The patient may experience difficulty in climbing stairs or tying their shoelaces. This is in contrast to osteoarthritis of the knee in which the ligaments tend to become lax.

How is osteoarthritis diagnosed?

Diagnosis is usually based on the symptoms, signs and X-ray changes. Blood studies are used mainly to rule out other causes of arthritis. X-rays may be normal early on, but are characteristic in later disease. Therefore a clinical examination and X-rays are the most important aspect of the diagnosis – not the blood tests.

Can it be prevented?

No, however, by remaining active and taking care not to become overweight, the severity of the disease can be lessened. However, early identification of risk factors such as hypermobility is important.

How is it treated?

Exercise

Patient education is particularly important. In spite of pain, it is important to keep active. Exercise maintains range of motion, and develops the stress-absorbing muscles and tendons. Daily stretching exercises are very important. Partial or complete immobilisation of a joint for relatively short periods can accelerate osteoarthritis and worsen the clinical outcome.

Interestingly, progression of osteoarthritis of the hips and knees can be retarded by a well-planned exercise regime.

Medication

These are divided into symptomatic and disease modifying therapies. Symptomatic therapies include analgesics – painkillers; such as paracetamol, and paracetamol/codeine preparations or even stronger opiate type drugs, such as tramadol  which treat pain alone. These drugs are very safe and may provide sufficient relief. Anti-inflammatories, NSAIDs, which treat inflammation and pain, include aspirin and other non-steroidal anti-inflammatory drugs. These are potentially hazardous to the stomach. Newer safer drugs called COXIBs are available, including Celebrex and Arcoxia. These are less damaging to the lining of the stomach. Cardiovascular safety of these drugs is, however, still under scrutiny and they should be used with caution in those with heart disease, high blood pressure, or strokes.

Oral cortisone is not helpful in osteoarthritis, but cortisone injections into the joint are useful when there are signs of inflammation. However, these are usually only needed occasionally.

There is some evidence that glucosamine sulphate has a role to play in pain and stiffness management. It is made from shrimp and crab shells and can therefore not be used if the patient has seafood allergy. Chondroitin sulphate (made from bovine cartilage) may add some small further benefit.

Drugs such as antimalarials, tetracyclines and metalloproteinase inhibitors are in trials for disease modification in osteoarthritis.

Hyaluronan injections are lubricants similar to joint fluid, made from rooster comb. These are expensive and are not proven to work. They are therefore not currently recommended for widespread use.

Surgery

Surgery for damaged joints is very successful, with hip and knee replacements now commonplace operations. Hip replacement restores mobility and relieves pain in at least 95 percent of cases. Hip replacements last for at least ten to 15 years.

Other joints, such as the small joints of the fingers and even the shoulder joint are also being replaced with increasing success. A particularly successful operation can be performed for advanced osteoarthritis at the base of the thumb. An expert hand surgeon is able to craft an alternative joint surface using the patient's own tissues.

Indications for surgery are joint pain non-responsive to medical therapy, or function impairment. Age alone is not a contra-indication to surgery, but joint replacement is usually deferred in younger patients where possible.

Outcome

With the correct approach of remaining active and keeping a check on weight, osteoarthritis need not become a disabling condition. However, the damage to the joints usually starts before symptoms arise, making it difficult to act early.

When to see your doctor

Consult your doctor if:

  • A joint is becoming increasingly painful and swollen.
  • You experience sudden extreme pain or immobility in a joint.
  • You have experienced pain and swelling in your knee(s) and it now starts to give way on movement, particularly when going up and down stairs.
  • You know that you have osteoarthritis of your weight-bearing joints, are overweight and would like some advice on weight loss and exercise.
  • When you are no longer able to cope and suspect you need replacement surgery.

Reviewed by Dr Ingrid Louw, MBChB, MMed (Int), rheumatologist/physician, (private practice), June 2011

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