Osteoarthritis of the knee

The bone at the edge of the joint grows outwards forming bony spurs called osteophytes. This can affect the thigh bone, the shin bone or the patella.

• The synovium may swell and produce extra fluid, causing the joint to swell. This is sometimes called ‘water on the knee’.
• The capsule and ligaments slowly thicken and contract – as if they were trying to push the joint back into shape.

In some joints the body’s ‘repairs’ are quite successful and the changes inside the joint won’t cause much pain. But in osteoarthritis of the knee the repair doesn’t usually work very well.

You may have pain all around the joint or just in a particular place, most likely at the front and sides of the knee, and it may be worse after a particular movement, such as climbing stairs. The pain is usually better when you rest. It’s unusual to have pain in the knee which wakes you up at night, although this sometimes happens with severe osteoarthritis. You’ll probably find that your pain will vary and that you have good days and bad days – sometimes depending on how active you’ve been but sometimes for no obvious reason.

The joint may not move as freely or as far as normal, and it may creak or crunch as you move. If the osteoarthritis is severe the knees may become bent and bowed. Sometimes the joint gives way either because the muscles have become weak or because the ligaments are damaged. Exercises to strengthen the muscles can often help to prevent the knee giving way.

• Age – Osteoarthritis usually starts from the late 40s onwards. We don’t fully understand why it’s more common in older people but it’s probably due to factors like weakening of the muscles and the body being less able to heal itself.
• Sex – Osteoarthritis of the knee is twice as common in women as in men. It’s most common in women over the age of 50 although there’s no strong evidence that it is directly linked to the menopause. It is often associated with mild arthritis of the joints at the ends of the fingers (nodal osteoarthritis) which is also more common in women.
• Obesity – Being overweight is an important factor in causing osteoarthritis generally, but especially in the knee. It also increases the chances of osteoarthritis becoming progressively worse.
• Joint injury – Normal activity and exercise don’t cause osteoarthritis, but very hard, repetitive activity or physically demanding jobs can increase the risk. Injuries to the knee joint often lead to osteoarthritis in later life. A common cause is a torn meniscus or ligament which can result from a twisting injury. This is a common injury in footballers, and an operation to remove the torn cartilage (meniscectomy) also increases the risk of osteoarthritis.
• Genetic factors – Genetic factors play a part in osteoarthritis of the knee. The genes we inherit may affect collagen, one of the important components of cartilage, or the way the bone reacts and repairs itself, or even the inflammatory process.
• Other types of joint disease – Sometimes osteoarthritis is a result of damage from a different kind of joint disease, such as rheumatoid arthritis, that occurred years before.

Osteoarthritis can sometimes develop more quickly and cause a lot of damage to a joint, which may cause some deformity or disability. This is more likely to affect older people with a severe form of the disease. The pain can increase with a reduction in mobility within a few weeks or months. But this is rare and occurs in less than 1 in 20 people with osteoarthritis.

In severe osteoarthritis the cartilage can become so thin that it no longer covers the ends of the bones. The bones start to rub against each other, and eventually to wear away. The loss of cartilage, the wearing of bone, and the bony spurs can alter the shape of the joint, forcing the bones out of their normal alignment and causing deformity.

In addition, the muscles that move the joint gradually weaken and become thin or wasted. This can make the joint unstable so that your knee gives way when you put weight on it.

Changes in your lifestyle can greatly reduce the risk of osteoarthritis of the knee progressing. Regular exercise, protecting the joint from further injury and keeping to a healthy weight will all help.

Osteoarthritis doesn’t lead to rheumatoid arthritis or other types of joint disease and won’t spread through the body. Nor is osteoarthritis linked with cancer or other serious illnesses, although some people with osteoarthritis will develop other illnesses purely by chance.

Osteoarthritis with crystals                        

A fairly common complication is where chalky deposits of calcium crystals form in the cartilage. This is called calcification or chondrocalcinosis. It can happen in any joint, with or without osteoarthritis, but it’s most likely to occur in a knee that’s already affected by osteoarthritis, especially in older people. It can cause a sudden flare-up of pain and noticeable swelling of the joint. The crystals will show up in x-rays and they can also be seen in samples of fluid taken from the joint.

Osteoarthritis tends to become more severe, and more quickly, when there are crystals present. And sometimes the crystals can shake loose from the cartilage, causing a sudden attack of very painful swelling called acute calcium pyrophosphate crystal arthritis (pseudogout).

Baker’s cysts (popliteal cysts)

Baker’s cysts can form when the joint has been damaged by arthritis. They are often painless, but you may be able to feel a soft lump at the back of the knee. Sometimes a cyst can cause aching or tenderness when exercising, or the knee may give way. Occasionally a cyst can press on a blood vessel, which can lead to swelling in the leg, or the cyst may burst (rupture), which can be very painful. Cysts can generally be treated by drawing off the extra fluid from the knee joint using a syringe (this is called aspiration) and injecting a steroid solution.

• tenderness over the joint
• bony swelling
• creaking of the joint
• restricted movement
• thinning of the muscle
• excess fluid
• instability in the joints

X-rays are the most useful test to confirm osteoarthritis, although often they won’t be needed. An x-ray may show changes such as bony spurs or narrowing of the space between the bones. They will also show whether there are any calcium deposits within the joint. However, x-rays are not a good indicator of how much pain or disability you’re likely to have. Some people have a lot of pain from fairly minor joint damage, while others have little pain from more severe damage.

Rarely, an MRI (magnetic resonance imaging) scan of the knee can be helpful – this will show the soft tissues (e.g. cartilage, tendons, muscles) which can’t be seen on a standard x-ray.

There are a number of tablets and creams that can help. And because they work in different ways you can combine different treatments if you need to. Your chemist can advise you and supply paracetamol, and some low-dose tablets and creams without a prescription. However, you will need a doctor’s prescription for stronger medications.

Painkillers (analgesics)

These often help with the pain and stiffness although they don’t affect the arthritis itself and won’t repair the damage to the joint. They are best used occasionally when the pain is very bad, or when you’re likely to be exercising. Paracetamol is usually the best painkiller to try first. Combined painkillers (e.g. cocodamol, codydramol) contain paracetamol and a second codeine-like drug and may be helpful for more severe pain.

Combined tablets are often stronger than paracetamol and are therefore more likely to cause side-effects such as constipation or dizziness.

Non-steroidal anti-inflammatory drugs (NSAIDs)

Your doctor may suggest a short course of NSAIDs (e.g. ibuprofen, naproxen) if inflammation in the joint is contributing to your pain and stiffness.

These are more likely than paracetamol to cause side-effects – including indigestion, diarrhoea, ankle swelling and skin rashes. You shouldn’t take NSAIDs if you’ve had stomach ulcers as there’s a small but significant risk of bleeding from the stomach. If you’re over 65 or if you smoke your doctor will probably suggest that you take another tablet (called a proton pump inhibitor) along with your NSAIDs to help protect the stomach. An alternative is a newer type of NSAID known as COX-2s or coxibs, although these aren’t suitable for people who’ve had a heart attack or stroke or who have uncontrolled high blood pressure.

NSAID creams and gels

You can rub these directly on to painful joints and they are especially helpful for osteoarthritis of the knee. If you have trouble taking tablets, NSAID creams may be a better option. These are extremely safe as very little is absorbed into the bloodstream.

Capsaicin cream

This is made from the pepper plant (capsicum) and is an effective painkiller. It needs to be applied regularly each day to be effective.

Most people feel a warming or burning sensation when they first use capsaicin but this generally wears off with regular use.

Stronger painkillers

You may need stronger painkillers (or opioids) such as tramadol, nefopam or meptazinol if you have severe pain and other medications aren’t providing adequate relief.

Stronger painkillers are more likely to have side-effects – especially nausea, dizziness and confusion – so you’ll need to see your doctor regularly and report any problems you have with these drugs.

Injections

Injections are sometimes given directly into a particularly painful joint:

• A steroid injection can start to work within a day or so, and may improve pain for several weeks or even months. The injection can be given either into a tender spot around the knee or even into the joint itself. This is mainly used for very painful osteoarthritis or for sudden painful attacks caused by the shedding of calcium crystals.
• An injection of hyaluronan into the knee may help a few people with knee osteoarthritis, although this isn’t often used. Hyaluronan is similar to normal joint fluid and is normally given as a course of injections once a week for 3–5 weeks, or occasionally as a single injection.

Surgery

Surgery may be recommended if pain is very severe and/or you have mobility problems. Many thousands of knee replacements are performed each year and the operations is usually very successful at removing pain and improving mobility.

Sometimes, if your knee locks, keyhole surgery techniques may be used to wash out loose fragments of bone and other tissue from the joint (this is called arthroscopic lavage). It isn’t recommended unless the knee locks). Additional procedures are occasionally carried out – such as smoothing the surfaces of the joint and trimming torn soft cartilage (this is called debridement). These techniques can’t repair the damage to the knee but may offer pain relief in the earlier stages of osteoarthritis.

Because of the way the joints work, the force put through your knee joints when you walk can be 5–6 times your actual body weight. So losing even a small amount of weight can make a big difference to the strain on your joints.

There’s no special diet that’s been shown to help specifically with osteoarthritis, but if you need to lose some weight we would recommend a balanced, reduced-calorie diet combined with regular exercise.

Strengthening exercises

will improve the strength and tone of the muscles that control the affected joint. Osteoarthritis of the knee can weaken the thigh (quadriceps) muscles. Exercising the muscles helps to stabilize and protect the joint, and has also been shown to reduce the pain.

• Aerobic exercise is any exercise that increases your pulse rate and makes you a bit short of breath. Regular aerobic exercise should help you sleep better, is good for your general health and well-being, and can also reduce the pain.

Choose exercises which you can do regularly. The easiest exercise can be done sitting in a chair. A physiotherapist can advise you on exercises but you’ll need to build them into your daily routine to get the most benefit from them.

Swimming can be very good for osteoarthritis. Because the water supports the weight of your body you won’t be putting a lot of strain on your joints as you exercise. Your physiotherapist may also recommend special exercises in a hydrotherapy pool. This can help get muscles and joints working better and, because the water is warmer than in a typical swimming pool, it can be very soothing and relaxing for the joints and muscles.

Straight leg raise (sitting)

Get into the habit of doing this every time you sit down.

• Sit well back in the chair with a good posture
• Straighten and raise one leg
• Hold for a slow count to 10, then slowly lower your leg

Repeat this several times with each leg – at least 10 times with each. If you find you can do this easily, try the exercise with weights on your ankles.

Straight leg raise (lying)

Get into the habit of doing straight leg exercises in the morning and at night while lying in bed.

• Bend one leg at the knee
• Hold the other leg straight and lift the foot just off the bed
• Hold for a slow count of 5, then lower.

Repeat 5 times with each leg every morning and evening.

Muscle stretch

Do this at least once a day when lying down. Not only does this exercise help to strengthen the quadriceps muscles, but also it prevents the knee from becoming permanently bent.

• Place a rolled-up towel under the ankle of the leg to be exercised
• Bend the other leg at the knee
• With the straight leg, use your leg muscles to push the back of the knee firmly towards the bed or the floor
• Hold for a slow count of 5

Repeat 5 times with each leg.

Clenching exercises

During the day, whether standing or sitting, get into the habit of clenching and releasing the quadriceps muscles. By constantly stimulating the muscles, they become stronger.

• Pace your activities through the day – don’t tackle all the physical jobs at once. Break the harder jobs up into chunks and do something gentler in between. Keep using your knee, but rest it when it becomes painful.
• Wear low-heeled shoes with thick soft soles. Thicker soles will act as ‘shock absorbers’. High heels will alter the angle of the hip, knee and big toe joints and put additional strain on all these joints.
• Use a walking stick to reduce the weight and stress on a painful knee. A therapist or doctor can advise on the correct length of the stick.
• Use the hand-rail for support when climbing stairs. Go upstairs one at a time with your good leg first. Come downstairs with your bad leg first.
• Don’t keep your knee still in a bent position for too long as this will eventually affect the muscles.

Glucosamine and chondroitin

Many people find glucosamine and chondroitin tablets helpful. These are compounds that are normally present in joint cartilage, and there’s some research that suggests that taking supplements may improve the health of damaged cartilage. Glucosamine is available from your chemist or health food store. You’ll need to take a dose of 1.5 g of glucosamine sulphate a day and you may need to take them for several weeks before you notice any pain relief.

Most brands of glucosamine are produced from shellfish. If you’re allergic to shellfish make sure you take a vegetarian or shellfish-free variety.

Acupuncture

Acupuncture has been shown to provide relief from pain, although the effect may be short-lived. For longer-lasting benefits, you’ll need to have regular sessions of acupuncture.

It’s important to tackle problems like these as they could lead to depression and will certainly make the osteoarthritis itself more difficult to cope with. Keeping active should help, but it’s worth speaking to your doctor if you do find your arthritis is getting you down.