Wherever there is sport, there are injuries. The pavement in a large public running event can look like one long queue for the physiotherapist. Every few hundred metres, someone is sitting on the kerb rubbing their ankle or hobbling out of harm's way having done in their knee.

The phenomenon extends to all sports. Get a group of cyclists or footballers together and it doesn't take long for them to start swapping injury stories. For Tom, 39, a business development manager, first it was his right knee, from running; then his lower back from five-a-side; then his ankle from jogging on muddy, uneven ground. "I was so angry with myself," he says. "I was determined to get fit again, but every time I started doing stuff, I injured myself again."

Katie, a civil servant who is out running or cycling every weekend, can relate to that. "I was told I had the ankles of a 60-year-old when I was in my mid-thirties," she says. She has had two broken ankles, shin splints, a hip injury and a bad back during 20 years of sustained exercise, particularly orienteering and running. "I've learned a lot of lessons," she says. "In my teens and early twenties, I wouldn't let things heal and would go back into training far too hard after an injury. Now I'm better at listening to what the pain is trying to tell me."

These days, Katie wears good-quality trainers, never runs on tarmac and does t'ai chi and Pilates to aid her balance and core strength. She believes that exercises can be avoided by being honest with yourself. "When someone starts an exercise plan, they need to be realistic about what they can do. The lesson is: listen to your body, start things gradually - and if you're going to invest in one thing, make sure it's your shoes."

Those are Dr John MacLean's sentiments exactly. The medical director of the sports injury clinic at Hampden Park, Glasgow, says: "It's the one piece of advice I would give anyone who's doing exercise: spend a decent amount of money on a good pair of shoes." So whether you're a runner or a player, get the shoes for your sport.

In a good pair of shoes, when you stand on your toes, you should feel no pressure from the shoe on your Achilles tendon. You should also change your shoes every 500km of running - or, if you're doing gym classes, every 100 hours. The older and more used they get, the less support they provide.

Shoes aside, though, is it not inevitable that someone who exercises regularly will eventually injure themselves? Not at all, says Catriona Shaw. The sports and exercise medicine manager at Edinburgh University's Fitness Assessment and Sports Injury Centre says: "Exercise is to be encouraged. You just have to be cautious how you go about it."

Generally speaking, there are two types of sports injury: traumatic injuries, from collisions, tackles or going over, and over-use injuries. Furthermore, several factors influence your chances of getting hurt. Some sports are associated with more injuries than others: Shaw says that she and her colleagues see a lot of trauma injuries from contact sports such as rugby, football and hockey. In addition, a muddy, icy or bumpy surface on the pitch or track increases your chance of skidding or falling.

Then there are factors specific to the individual, such as age, sex, weight and level of general fitness. Anatomical variations, such as high arches or flat feet, and muscle imbalances (tennis players tend to have one very muscled arm) can also increase the injury risk. Perhaps the biggest single factor, though, is failure to let old injuries heal properly.

Read on to find out how to minimise your chances of getting injured while exercising.

Ankle
There are two common injuries. The first is ankle ligament injury, for instance from going over on your ankle. When you do go over on an ankle, Dr MacLean explains, you not only tear your ligaments but damage your proprioceptive fibres - that is, sensory receptors that help you keep your balance. By training your body to keep its balance more effectively, you can help prevent injury.

To improve balance, stand on a rolled-up towel or wobble-board (hemisphere with a board on top) while holding on to a work surface, then wobble from side to side and back and forwards. This will help retrain the proprioceptive fibres and make you less likely to go over.

The other common ankle injury is Achilles tendinopathy, where you get repeated microtears in your tendons ("think of a big bundle of dry spaghetti with a few broken strands in it" says MacLean). This is normally related to unusual foot shape, bad footwear or overdoing things. "Once you've developed a predisposition to it, it just sets up a cycle," says MacLean.

For good strong ankles, have a realistic training programme. Don't increase intensity and distance at the same time. "If you're running eight-minute miles on the flat, don't suddenly start doing seven-minute miles uphill."

Knee
Common injuries are of the collateral ligaments, on either side of the joint, and the cruciate, a cross-like structure inside the knee that controls how the bones join. When it gets ripped, the stability of the joint is compromised. Other problems include cartilage injuries, caused by slipping or twisting, and injuries around the kneecap.

To protect the knee, work on strength, flexibility and muscle balance; for instance, it is important to ensure the quads and hamstrings are equally developed. Pilates and plyometrics (a type of training that increases muscle power and strength) are good for this. It is also good to do a mixture of different sports in a week, such as swimming and Pilates, along with running. And pay attention to those aches and pains: "There's no such thing as a wee strain or mild sprain. You have to take them seriously," says MacLean. "Cut back the intensity and frequency of your exercise until it has healed."

Foot
Plantar fasciitis is inflammation of the soft tissues that stretch from the toes to the ankle underneath the foot. It causes heel pain, particularly on the inside of the foot. "People start a repetitive activity and get tears in their plantar, and it gets exacerbated," says MacLean.

People with unusually shaped feet or who "overpronate" (whose feet roll inwards too much) are particularly susceptible. Bunions are another problem. The most important thing for healthy feet is a good pair of shoes, says MacLean. See a podiatrist if problems persist.

Groin
Groin strains tend to arise in twisting, turning sports such as rugby, football and running. They are one of the hardest things to diagnose. Building core stability can help prevent groin strain, says MacLean. This involves targeting smaller lumbar spine and trunk muscles. Physiotherapists and fitness instructors can recommend exercises, and many books are available that will also help.

General