Getting injured is one of the desperately unfair things about exercising. There you are, doing your body a favour, and how does it repay you? With a gammy knee. I had been running two or three times a week for a year when my knees started going funny. Too impatient to wait for an appointment with an NHS physiotherapist and too tight to sign up for long-term private treatment, I simply stopped running. Until, that is, I learned that I could help myself.

"There are ways of administering physio to yourself," says sports and rehabilitation specialist Dan Burt. All I needed, he told me, were three simple pieces of equipment. You do need to get checked out by a qualified physiotherapist before you embark on this self-help programme, and if possible, book a session with a sports injury specialist who will show you how to use the equipment properly.

The roller (From £10)

This unassuming foam sausage can help knee and lower-back problems, by relieving the tightness that can lead to muscle imbalance. After just a week of twice-a-day rolling, for no more than five or 10 minutes at a time, my knee was much better and I was back running.

Here's what you do: lie on your side with one thigh on the roller and the other leg balanced on top of it. Twizzle yourself around so you are facing the floor, with your hands shoulder-width apart and flat on the ground. Carefully roll back and forth, massaging your thigh from your knee to your hip (if you have a lot of tightness this will be painful, but stick with it). Work different angles on both legs, aiming for 10 sets back and forth on each one.

The key to this, says Burt, is to "keep your body streamlined and parallel to the floor, work from the knee all the way to your hip and don't let your feet touch the floor". Ideally, he says, you want to do this daily, plus after any exercise sessions.

The reflex massage ball (From £15)

Really it's just a spiky rubber ball that you sit on and use to massage your gluteal muscles. Your bum, that is. Until I met Burt, I thought that having a tight bottom was a desirable thing, but it turns out that tight glutes can be the cause of all sorts of nasties, including my knee pain. "Loss of function in the stability triangle of the pelvis can lead to spinal dysfunction and therefore pain," says Burt.

It's easy to use. Just balance your right buttock on the ball, put your left foot on the floor and rest the other foot on your left knee. Putting all your weight on the ball, roll around until you find the bits that hurt. These are often in a triangle towards the outside of your hip. Once you've located the painful spots, keep rolling over them until you can't bear it any longer, then switch cheeks. When it gets too easy, you can swap it for a smaller ball.

The calf stretcher (From £30)

You can, of course, just stretch your calves without equipment, but this nifty little rocker will stop you over-stretching. Tight calves can be harmful if you're running a lot, says Burt, "because it alters the mechanics of the stride, stressing other muscles and tendons in the body".

All you do with this one is find a wall to lean against, stand with one toe against the wall and the other foot on the calf stretcher. Making sure your heel is pressed to the back of it, drive your heel down into a stretch.

"Don't let your bum stick out, and make sure that your feet are parallel so that your hips are straight on," says Burt.

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