I am three weeks into a running programme and my left knee is very painful. Ibuprofen and ice barely help. How can I strengthen my knee?

There is rarely a single cause, and so solution, to a knee problem. Bursitis (inflammation of the paddy tissue underneath the kneecap) is a common runners' problem which you can self-diagnose by walking slowly up and down stairs: if you get pain in the knee only when you step down, you've got bursitis - if so, apply the "rice" principle (rest, ice, compress and elevate) and don't run for a while; instead, take a brisk walk.

Muscular imbalance on the inside and outside of the joint is another common cause. Try this exercise which targets the weaker medialis muscle of the quadriceps around the inside of the knee. Tie a Dyna-Band securely around your right knee and attach it to something stable, such as a table leg. Stand with your left foot behind you, heel slightly raised. Slowly bend your right knee, making sure it is correctly aligned over your foot, with the mid-line of the knee in line with your second toe, then straighten the leg. Repeat 12-16 times.

Often, the cause of such a problem is not even the knee itself, but rather the foot. Fallen arches can exacerbate poor alignment, causing the foot to roll in with each strike, thereby putting pressure on the knees. Rectify this with toe curls: with bare feet on a carpet, curl your toes 15-20 times, imagining you're trying to pick up a pencil with them. A good podiatrist can provide orthotic supports for persistent knee problems, but I'd try to address the root cause of the problem first.

· Joanna Hall is a fitness expert (joannahall.com). Send your exercise questions to Weekend, 119 Farringdon Road, London EC1R 3ER (weekend@theguardian.com).