Gout!

Found this article for you seems the cherry idea is right.

Gout is an arthritic condition caused by swelling of the joints that often strikes out of the blue and can be extremely painful.

However, the good news is that this is the only form of arthritis where there is clear medical evidence showing that a change in diet can result in significant benefits.
The problem with purines
"Gout is caused when crystals of uric acid – a natural waste product in the body – form in the joints," explains Kate Di Prima, spokesperson for the Dietitians Association of Australia. "Food that contains high levels of purines produces more uric acid, so start by avoiding those if you suffer from gout."

She lists red meat, offal and sweetbreads, gravy, stock cubes and yeast extracts such as Vegemite on her no-go list. Some shellfish and certain fish such as herring, sardines, mackerel and anchovies are also high in purines, which are natural chemicals found in both plant and animal cells.

Unfortunately, these are also the oily fish containing omega-3 fats, found to reduce inflammation with some forms of arthritis. However, foods rich in omega-3 also include linseeds, linseed and canola oil, and walnuts.
In the drink
Excess consumption of alcohol (and especially beer) and binge drinking are linked to gout, so suffers should limit their alcohol intake to a standard drink a day, and preferably stick to wine. During an acute attack of gout, it is best to cut out alcohol altogether.

Coffee is more confusing. "Both regular and decaffeinated coffee may lower your uric acid level and reduce your overall risk of gout," says Kate Di Prima. "However, a sudden large intake may actually trigger an acute attack. If you choose to drink coffee, keep to a regular daily intake of no more than four cups."
The good food
While purine-rich foods and alcohol are to be avoided, some foods may actually be good for patients with gout. "A popular remedy is the cherry cure," says body+soul naturopath expert Mim Beim. "Cherries contain anthocyanidins which help lower uric acid. Eat a cup of cherries, either fresh or canned, each day. Strawberries and blueberries are also good."

She also says herbs that increase uric acid excretion include nettle leaf, gravel root, parsley, celery seed and birch. "Drinking herbal tisanes containing nettles helps rid the body of excess uric acid. And a juice made of two-thirds carrot, one-third celery and several sprigs of parsley may help relieve the inflammation during an attack."
Alcohol, overeating, dieting and dehydration can trigger a gout attack," says Dr John Carnie, Victoria's Chief Health Officer. "Reduce excess body weight. Cut down on excessive alcohol consumption, drink plenty of water and avoid fructose, found in many soft drinks."

Overall, he says, gout suffers can take heart. "Healthy lifestyle choices combined with a correct treatment program should mean that gout can be successfully managed."

Nettle leaf tea is a folk remedy. I can't vouch for it's efficacy.
Wear gloves to collect the nettle leaves (obviously). Boiling/drying them will remove the stings.