Doctors say runner's knee is one of the most frequently encountered complaints at sports medicine clinics.
It is the layman's term for patello-femoral pain syndrome or chondromalacia patella, a name given to conditions of the knee that have a number of causes.
Though so named, it is suffered not only by runners, but is commonly experienced by a healthy person in middle age, after he has spent many years overusing the knee joint in vigorous activities, causing joint irritation.
Older runners, from their mid-30s, may have knee pain from ulcers in the knee cartilage caused by sports trauma or due to cumulative injuries to the knee as they get older.
Some may eventually develop pain from osteoarthritis, which is degeneration of the knee caused by wear and tear.
Runner's knee is one of the most frequently encountered diagnosis in sports medicine clinics and affects up to 25 per cent of active people, said Dr Mohamed Fadzil Hamzah, resident physician at Changi Sports Medicine Centre at Changi General Hospital (CGH).
It can also be experienced by the younger athletic population whose knees are still structurally sound but who tend to have knee pain due to overuse, said Dr Jason Chia, head of the sports medicine and surgery clinic at Tan Tock Seng Hospital.
This can be aggravated by physical factors, such as muscle tightness and alignment problems and problems in running gait, he added.
The condition is also sometimes seen in young runners, such as teenagers.
They could suffer from pain resulting from inflammation in areas where the tendon (band of fibrous tissue that connects muscles to the bones) joins the bones in the knee joint. Said Dr Chia: "These areas, being mechanically weaker in the immature skeleton of the adolescent, can sometimes become inflamed through overuse."
Most running injuries are accumulative and result from the training load exceeding the body's capacity to deal with this load, he said.
He estimates that one in three of his patients come to him because of knee pain.
It does not affect just runners but also those who do daily activities or exercises that put heavy stress on the knees or require repetitive knee bending, such as walking, squatting, jumping and cycling, said Dr Fadzil.
When activity hurts
Runner's knee results in various symptoms.
In all cases, there is pain in the knee joint, said Dr Fadzil.
This is often in the form of a dull, aching pain under or around the front of the kneecap (patella) where it connects with the lower end of the thighbone (femur), he said.
The pain tends to worsen with knee activity, he said.
It may also be felt with prolonged sitting with a bent knee in cramped conditions, such as in lecture theatres or vehicles, and is often referred to as a "moviegoer's sign", he said.
There may be a "catching" sensation accompanied by sharp pain and momentary weakness, often perceived as a sensation of the knee giving way.
Some people may also complain of a rubbing (crepitus), grinding or clicking sensation when they bend and straighten the knee, said Dr Fadzil.
Occasionally, the knee joint may become swollen.
Runner's knee is usually diagnosed through a complete medical history and a physical examination.
The doctor will ask the runner about his symptoms and the types of sports or activities he does.
"Be sure to tell your doctor if you have increased the duration, frequency and intensity of your activity, or if you have recently engaged in a new sport," said Dr Fadzil.
The doctor will examine the alignment of the knee cap, thigh and the lower leg; the range of motion of the knee; signs of tenderness around the knee cap or any dislocation of the knee cap, he added.
The patient may be asked to squat, jump, walk or lie down so that his gait and the knee's strength and mobility can be assessed.
Imaging tests, such as X-rays or magnetic resonance imaging scans, may be ordered if the doctor suspects that the structures of the knee and the surrounding tissue are damaged, or if there is any doubt about the diagnosis.
Surgery not the treatment
Most runners with knee problems respond to non-surgical treatment, which varies according tothe underlying problem, said Dr Chia.
They could undergo rehabilitative exercises that aim to strengthen and stretch the muscles around the knee or have their running technique analysed and altered.
Sometimes, a change of shoes, use of orthotic devices (supports) or braces can help.
Patients can also receive treatment to promote tissue healing such as shock-wave therapy, said Dr Chia.
Delivered in pulses, the shock wave (sound wave) stimulates metabolism and improves blood circulation to facilitate the healing and regeneration of damaged tissue.
A minority of patients, especially if they do not respond to non-surgical treatment, may end up with surgery.
"But this number is probably fewer than one out of 10 patients," Dr Chia added.
To reduce the risk of runner's knee, the body must be conditioned to be able to take the repetitive high impact of running.
Dr Fadzil and Dr Chia give tips on how to prevent runner's knee.
Ms Melanie Tan, a sports trainer at the Changi Sports Medicine Centre at CGH, demonstrates some stretching and strengthening exercises for the knee.
Stretching and strengthening exercises for the knee
Outer thigh muscle stretch
This stretch conditions the body to take the repetitive impact of running.
You should do these exercises every other day on at least two or three days of the week.
1. Lie on the ground on the left side of your body. Lift your upper body and support it with your left arm.
Bend both your knees. Tuck the knee of the right leg behind the knee of the left leg.
2. With your right arm, reach back and pull on the right foot until you feel resistance (front view, top; back view, bottom).
3. Hold the position for 30 seconds before releasing the leg .
4. Do the stretch 15 to 20 times.
5. Switch sides and stretch the other thigh muscle for 15 to 20 times.
Hip, thigh and knee muscle stretch
This exercise conditions the body to take the repetitive impact of running by stretching the iliotibial band.
This is a band of tissue that runs along the outside of the hip, thigh and knee.
1. Stand with both feet on the ground. Cross your left leg over your right leg at the ankle.
2. Extend your right arm overhead, reaching toward the left side.
You will feel a stretch along your right hip.
3. Hold this position for about 30 seconds before relaxing.
4. Switch sides and repeat the exercise.
5. Repeat the whole process for 15 to 20 times.
Hip muscle stretch
Stretching the external hip rotators in the hips can help with overall mobility and keep you pain-free.
1. Sit on the floor with both legs stretched out in front of you. Bend the left leg and cross the left foot over the right leg, placing it beside the right knee.
2. Hold the left knee with both hands and push it gently towards you, as you bend forward from the hips. You should feel a good pull in the left hip and buttock.
3. Hold the position for 30 seconds before releasing.
4. Do the exercise 15 to 20 times.
5. Switch sides and repeat the exercise.
The wall squat, which may be performed daily, strengthens the thigh muscles called the quadriceps.
Weak quadriceps are one of the top causes of runner's knee.
1. Lean against a wall and slide your back down it. Move your feet forward as you do so until your thighs are at 90 degrees to your calves.
2. Hold this position for 30 seconds, before standing up.
3. Slowly increase the duration of the squat until it reaches three to five minutes.
•Increase the training load, such as the running distance, by a moderate amount. Vary the quantity of the training load so as to create periods of training at a lower intensity, to allow the body to recover.
•If there is a need to change your running technique, it has to be done slowly to allow the body to adapt. It should be done with corresponding strengthening exercises and the use of correct running shoes that suit your feet and running style.
•Stretch and strengthen the muscles in the hips, thighs and knees. Good general conditioning is important to control and prevent knee pain.
•Maintain a healthy weight to reduce the stress that knees undergo as a result of daily physical activities. Excess body weight puts undue strain and stress on all weight-bearing joints, especially the knees.
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