In June 2008, US golfer Tiger Woods tore his anterior cruciate ligament (ACL), which goes across the front of the knee and controls the movement of the joint, while playing at the US Open. The injury ruled him out for nine months, a lifetime in sports. Brazilian football icon Kaka suffered a cartilage tear in the knee that threatened to end his career in June. After a tricky operation, Kaka spent four months in rehabilitation. Rafael Nadal’s knee sprain stopped him from defending his Wimbledon title in 2009, and forced him to retire from the 2010 Australian Open quarter-final match against Britain’s Andy Murray.

The impact on the knees while running is four-six times that of the runner’s body weight.

“In most impact sports like football, tennis, cricket or running, knees are more likely to be injured than any other part of the body because of the sheer amount of forces at work on the joint," says Pushpinder Bajaj, head of arthroscopy and sports medicine at Primus Super Speciality Hospital in New Delhi. “In running, for example, the force the knees are absorbing is four-six times that of the runner’s body weight."

“Most knee injuries occur due to overuse or uneven distribution of forces," says Jaya Shahani Radhwani, senior physiotherapist at the A+ Orthopaedic and Sports Medicine Clinic in south Delhi. “If your quadriceps (thigh muscles on the front of the leg) are not strong, your core muscles are weak, or your hamstrings are tight, it puts too much stress on the knee."

Here is what you can do to protect your knees during three common athletic activities.


This is one of the most high-impact activities that the knee can go through, especially if it’s done on a hard surface such as concrete or asphalt. Incorrect technique or stride, overpronation (where the foot rolls more than necessary on impact) and bad posture are the most common causes for knee injuries.

“You should land on the middle of the foot first and then the heel in a straight line," says Dr Radhwani, “and the foot should drive up towards the buttocks to propel you forward. Strides should be kept short, and the body should be in a straight line, with the shoulders pulled back and down, the back straight and the stomach muscles tightened a little."

“A lot of people get runner’s knee, a condition where there is severe pain under the kneecap, because they are running with improper footwear or on hard surfaces," says Dr Bajaj. “Run on grass or earth or soil tracks, and for any serious runner, it is important to change shoes (after) every 500km."


The constant change in speed, breaking, turning, and lateral movements needed to play tennis exert heavy stress on the knee joint. Most movements also have to be done quickly, without much reaction or preparation time, increasing the chances of injury.

“Tennis players are susceptible to two main types of injuries," says Dr Bajaj, “meniscus (cartilaginous structures that distribute the body weight evenly across the knee joint) tear because of lots of pivoting movements, when the body rotates and the knee can’t hold up, and ACL injuries are for the same reasons."


Golf, which is usually considered a low-impact sport, actually puts almost as much stress on the knees as tennis or running, according to a 2008 study done by the Orthopaedic Research Laboratory at Scripps Clinic, California, US.

“The rapid pivoting movement while driving the ball puts a lot of stress on the ligaments in the knee joint," says Dr Radhwani, “and meniscus injuries are very common as well." The combination of driving, standing for hours, and walking long distances puts more stress on the knees.

The complete knee package

Strengthening the knee joint involves strengthening and limbering the muscles, ligaments and tendons that support the joint. According to Dr Bajaj and Dr Radhwani, there are four main areas of concern no matter what sport you play: the flexibility of muscles and ligaments, the agility to adapt to different postures and motions, the strengthening of muscles that support the knee, and the endurance level of muscles.

“To increase endurance without damaging your knees, it is best to mix high-impact cardiovascular exercises like running with non-impact cardio activities like swimming or working out on the cross-trainer," says Dr Bajaj.


Always warm up with some gentle cardio activity like a brisk walk before stretching. Include running backwards (always landing on the balls of the foot, with the knees bent), and running sideways as part of the warm-up to improve lateral movement.

For the hamstrings, place one leg on a raised surface around waist-high. Keep the raised leg straight, and the other leg slightly flexed at the knee, and lean forward with the torso in a straight line over the raised leg and try and touch your toes with both hands. Hold for 10 seconds, then alternate.

For the quadriceps, stand straight with a wall or a support on your side. Hold the support gently with your right hand, and bend your left leg back from the knees so that the heel of the foot touches the buttocks. Grab the top of the foot with the left hand and hold for 10 seconds. Repeat with other leg.

For calves, stand facing a wall, with your left foot shoulder-length behind your right foot. Lean into the wall, with both palms flat on the wall and the back straight. Bend the right foot a little and press hard on the wall, keeping both feet firmly on the ground, till you feel a gentle stretch on the left calf. Hold for 10 seconds, repeat with other leg.


Squats: Stand with legs shoulder-width apart in a straight line. Squat as if you are going to sit, with your weight mostly on the heels, and the back kept straight. Stand up slowly with both feet grounded throughout. Three sets of 10 repetitions.

Lunges: Stand with one leg behind the other, and a little more than shoulder-width apart, and torso in a straight line with leading leg. Bend the back leg with the knee pointing straight towards the ground, lower the knee almost till the ground. Your torso should be straight, and the knee of your front leg should be in line with the toes, not extending beyond them. Straighten to starting position. Repeat 15 times with one leg, then switch.

Single leg raise: Lie flat on your back, with one leg bent at the knees and foot flat on the ground. Keep the other leg straight on the ground, and then lift it slowly about a foot off the ground, and then lower slowly. Repeat 20 times, then switch legs.


Stand in front of a step, hop up on the step using both legs and land gently on the balls of the feet, with knees slightly bent. Hop back down, again landing on the balls of the feet, knees slightly bent. Repeat 20-30 times.

Stand with the step on one side, hop sideways on to the step, hop back down. Repeat 20 times, then switch sides.

Proprioceptive exercise

These exercises help improve balance, and the awareness of the position of the limbs. Stand on one leg, with the knee flexed, for 30 seconds. Keep your arms spread on both sides. Switch legs. When comfortable with this, stand on one leg for 30 seconds with eyes closed, which makes balancing more difficult. To make it harder, stretch your arms straight in front.

Graduate to standing on one leg, and catching and throwing back a football or a medicine ball.