Overview

Osteoarthritis (OA) is a joint disease where there is progressive softening and disintegration of joint cartilage. With the loss of this articular cartilage, the exposed bone becomes the surface that bears weight and can be damaged. Bones involved come closer together, there is narrowing of joint space and new bone formation. As a result the bones rub against each other like grinding sandpaper. Thus, movement of the joint becomes painful and restricted.

Joints that are commonly affected are knee, hip and spine.
 

What is Cartilage?
Cartilage is smooth, white connective tissue up to 1/8 of an inch thick. It creates smooth, elastic and resilient surfaces that can rub against each other with very little friction. This is because it is kept moist by a substance called synovial fluid, produced by the synovial membrane inside each joint capsule.

Causes

There are 2 types of osteoarthritis:

• Primary
• Secondary

Primary OA develops for no apparent reason. It is mainly due to age and 'wear and tear'.  Elderly people tend to be more prone to Osteoarthritis. Patients with OA Knee joints are usually above 50 years old.

Secondary OA has more specific underlying causes. In such cases, joints are put under abnormal stress due to:

• Previous fracture or traumatic injury involving the joint or repeated stress to a joint (eg. athletes and ballet dancers)
• Abnormally shaped hips or knees
• Obesity

The following conditions result in direct weakening of the cartilage, which causes OA:

• Rheumatoid arthritis 
• Joint infection
• Gout

In some cases no direct cause is obvious.

What is Rheumatoid arthritis?

Rheumatoid arthritis is an autoimmune disorder where the body attacks itself such that there is inflammation of the lining of the joint (synovium) which progresses to joint damage and in few cases, deformity. Inflamed joints are painful and stiff.

What is Gout?

Gout is the most common of joint diseases. It is caused by the deposition of uric acid crystals in the joint, leading to inflammation and pain. This disease first attacks the big toe and then spreads to other joints. It is usually treated with painkillers as it can be controlled with drugs.  

Symptoms

You might have OA if you have:

• Extreme recurring pain- this is the leading symptom. It tends to be worse after activity. Because of pain, you tend not bear much weight on affected leg. Your thigh muscles may become weak and smaller.
• Joint stiffness- after rest, the joint feels stiff and it hurts to 'get going' after sitting for any length of time. In time, the joint gets stiffer and you may be unable to fully straighten or bend the joint.
• Swelling - this is common especially after excessive activity.
• Deformity- If the OA is severe, your joint may become deformed e.g. bowlegged (genu varus deformity)
• Redness- there is warmth in the joint 

Diagnosis

Diagnostic Tests

Osteoarthritis can be suspected in a patient with above symptoms. The diagnosis is confirmed through physical examination and x-rays, which will show degenerative changes to a joint.

Treatment

Non-Surgical

For mild cases of OA, treatment comprises the following:

Painkillers - Your doctor may prescribe simple painkillers eg panadol. If the pain is severe, stronger prescriptions like non-steroidal anti-inflammatory drugs (NSAIDs), eg synflex, ponstan, may be necessary. There should be used with care as they may cause side effects like stomach pain and stomach ulcers.

Corticosteroids (which have long-lasting effects) can be injected directly into the joint when it becomes so swollen and painful that movement becomes almost impossible. However, they can not be used for long periods of time due to adverse side effects.



Physiotherapy - Under physiotherapy, the exercise programme will help you strengthen your weak muscles and improve flexibility and range of joint motion. Heat therapy and other electrophysical modalities can be given to relieve pain. With improved muscular control and management of pain, physiotherapy will help you optimise your daily fuction. 

Weight reduction - Extra weight will add more stress on the already weakened joint and hasten degeneration. An obese patient will be advised to lose weight.

Walking aids - A walking stick/frame helps in reducing the load to the joint and will thus enable you to walk more comfortably.

In all cases, avoidance of strenuous high impact activities is recommended e.g. heavy manual labour, as that may aggravate your condition.

Surgical

If non-surgical measures have not been successful in relieving pain for cases of mild OA, surgery may be comsidered. Also, in more severe cases of OA, where the joint is unstable or progressively deformed, surgical measures may be a better option. The examples described below are for the knee joint, which is the most common joint affected by OA:
 
The aim of this operation is to trim or remove damaged cartilage fragments and loose debris from the joint so as to reduce pain experienced during movement. The bones may be drilled to stimulate new cartilage growth. It is usually performed on patients who are relatively young and are suffering from mild to moderate OA.

You will be put under anaesthesia, after which small incisions will be made in the knee joint, for the insertion of the arthroscope and other instruments. The arthroscope, a small rod-like instrument, acts like a camera that transmits magnified images of the knee joint onto the video monitor and guides the surgeon through the procedure. Sterile fluid is injected prior to the arthroscope insertion to expand the knee, making it more visible.

After surgery, only few patients require pain medication. The procedure can be carried out as a day surgery (with patient going home the same day if fit) or requiring a one to two day hospital stay. Upon discharge, you will be given instructions on what activities you should avoid and which exercises you should do to aid your recovery. You may require crutches to reduce the weight on your operated leg and limit discomfort.

Osteotomy - Less pressure is exerted on the affected part of the knee and hence alleviates the pain and improves the function of the knee joint.

You will have to be warded for between 5 days to one week, during which you will undergo gait training as part of physiotherapy.

Knee Replacement Surgery - In advance cases of OA, symptoms become so severe that joint replacement becomes necessary. Joint replacement surgery, as its name implies, replaces the damaged joint surface with an artificial joint.

This joint consists of a highly polished metal surface that mimics a roller, articulating against a smooth plastic block such that there is relatively little friction. These implants are cemented onto the ends of the knee joint using a special polymer. The surgery also realigns the leg so that the patient no longer has the "bow-legged" deformity.

Knee replacement surgery is definitely not minor surgery. However it is very safe If patients are well prepared. On average the surgery takes about 1 ½ hours to perform and patients seldom require any blood transfusion. The procedure can be done under general or regional anaesthesia.

Frequently Asked Questions about Knee Replacement Surgery

What do I expect during my hospital stay?

You will be admitted one day before surgery. The knee is expected to be painful for the first 3 days after surgery but morphine infusions will be prescribed for relief. The suction drains are removed on the second day after surgery and exercises are started to improve motion as well as to preserve muscle tone and strength. A continuous passive motion (CPM) machine is used to move the knee to avoid stiffness. By the fifth day most patients are expected to be out of bed and walking with the aid of a walking frame. The rest of the hospitalisation focuses on physiotherapy. You should be able to walk without aids by 4 to 6 weeks.

Can I walk normally after the knee replacement?

Patients walk very naturally after knee surgery. With correction of the knee deformity, there is relief of pain and an increase in range of motion. Thus, the patient attains a more efficient gait. However not all patients are able to squat and must be warned accordingly, especially Muslim patients who may desire to kneel for prayers. On average, most patients achieve a range of flexion from 0 to 115 degrees.
 
Is it costly? Is it cost-effective?

The average cost for patients in a government-subsidised B2 ward is $2500. This includes ward charges, meals, medication, surgery, radiographs and laboratory investigations. The knee prosthesis costs an additional $2500. The most commonly used implants are imported from the U.S.A.

There is a government subsidy of $500 towards the cost of the prosthesis for the B2 and the C class patients. In total, a B2 patient would expect a bill of about $4500. Almost the entire sum can be deducted from Medisave. A B1 patient would expect to pay a total of $10000. There will not be a subsidy for the prosthesis and part of the cost will have to be paid in cash.

Despite the cost involved, knee replacement surgery is highly cost-effective. When compared with other operations based on improvement in quality of life per dollar spent on surgery, knee replacement has been found to be amongst the most effective forms of surgery. Intangible gains such as the absence of pain and a sense of well-being makes surgery worthwhile. Less need for caregivers, medical care etc. will reduce long term health-care costs as well.
 
What are some of the complications patients should be aware of?

The most feared complication is wound infection. Treatment involves further hospitalisation, multiple surgeries to remove the implants and eradicate infection which will be difficult as well as costly. Fortunately, the infection rate for knee replacement surgery is very low (1%) as special precautions are taken such as the use of antibiotics, clean air flow in operation rooms etc.

Patients with impaired immunity (eg. rheumatoid arthritis patients on steroids; diabetics) would be at a higher risk and the risk-benefit ratio must be individually assessed in these cases. Other less common complications include blood clots in the leg veins (deep vein thrombosis), fractures, knee cap dislocations and injuries to the blood vessels and nerves (the risk is often under 0.5 %).
 
How long will the implant last?

Like all moving bearings, there is a problem of wear-and-tear as well as implant loosening. The last 10 years have seen many gains in manufacturing quality and design with improvements made to enhance fixation and reduce wear rate. Survivorship rate is a measure of the percentage of patients who require revision surgery to replace a loose or worn out implant after a period of time. Current published survivorship rates are 97% at 10 years and 95% at 15 years. Of course, the survivorship rate will vary according to the user and these rates generally apply to older patients (mean age - 65 years).