I have a Baker’s cyst behind my right knee, which makes it dif­fi­cult for me to walk. Would exer­cise help?

A Baker’s cyst is a swell­ing in the back of the knee which can grow as big as a ten­nis ball, mak­ing it very uncom­fort­able and dif­fi­cult to bend or fully straighten the knee. The cyst is filled with joint lub­ric­at­ing (syn­ovial) fluid which the knee has pro­duced in excess­ive quant­it­ies, because it is react­ing to some other under­ly­ing prob­lem in the knee.

Knees are pretty com­plic­ated and finely bal­anced struc­tures, and in the­ory any kind of dam­age could set off this over-​production of joint fluid. In prac­tice, a Baker’s cyst is often linked to a tear in the shock-​absorbing men­is­cal car­til­age (in younger people) or arth­ritis (in the over-​50s).

The first thing you need to be clear about is that the dia­gnosis of a Baker’s cyst is cor­rect: made by a pro­fes­sional and not some­thing you read on the inter­net. There are a couple of other behind-​the-​knee swell­ings that can be far more dan­ger­ous and need prompt med­ical atten­tion. So I am assum­ing that you have had the cyst checked out and con­firmed. Knowing what it is is half the story. You also need to know why it has appeared, because the only way to stop it com­ing back is to deal with the under­ly­ing prob­lem.

As for exer­cise, this is one of those cases when you need to avoid aggrav­at­ing the knee in order to help the swell­ing go down, which rules out most kinds of exer­cise. You can help your­self by fol­low­ing the “RICE” rules: rest, ice, com­pres­sion and elev­a­tion. Try to keep your weight off the knee, put your leg up whenever you are sit­ting and at night in bed. Short applic­a­tions of packs of frozen peas (10 minutes) and a stretchy band­age over the knee when you walk will help (but not too tight, you don’t want to burst the cyst). If you are able to take anti-​inflammatories, this might also help reduce the swell­ing. You are likely to have to take a break from exer­cise any­way to sort out whatever the under­ly­ing injury is. Concentrate on find­ing out and repair­ing this dam­age.

I do know, how­ever, that if you are used to doing reg­u­lar workouts, the idea of an enforced lay­off is always grim. So don’t give up alto­gether: rather, focus on some new chal­lenges. You can still, for instance, do upper body and core strength train­ing. You could use an arm-​cycle machine in the gym for a car­dio workout, or really chal­lenge your­self by prac­tising arms-​alone swim­ming strokes. Or perch on a stool and get to grips with jug­gling skills: fant­astic for sharpen­ing your co-​ordination and reac­tion times. And don’t for­get to rehab­il­it­ate your knee /​leg prop­erly once the mys­tery behind the cyst has been dealt with.