ONE day you are digging the garden. The next, you can barely get out of bed and brushing your teeth is the most you can manage, because of the searing pain in your limbs.
Welcome to the world of those who suffer from polymyalgia rheumatica (PMR), an inflammatory complaint which can strike out of the blue.
PMR occurs when white blood cells, which usually protect the body from harmful bacteria and viruses, attack the lining of the joints by mistake.
The pain and stiffness builds up over a week or two, making it difficult to function properly.
Climbing stairs, walking, and things like getting in and out of the bath all become a challenge, as previously active people suddenly find themselves housebound.
Even a simple tasks such as lifting a fork or spoon become impossible - and in severe cases, the pain can confine sufferers to bed.
In many cases, the first indications of the disease are flu-like symptoms which manifest themselves ahead of sudden and searing joint pain.
Prof Bhaskar Dasgupta, a consultant rheumatologist, based at Southend Hospital, is a leading international expert in the complaint and holds a weekly clinic at the hospital in Prittlewell Chase.
He believes awareness of PMR needs to be raised, because, along with the related condition, giant cell arteritis (GCA) - the most serious complication of PMR - it is often misdiagnosed With GCA, the arteries swell and become inflamed.
The arteries most commonly affected are those on the temple and inflammation leads to sudden and severe headaches, which if left undiagnosed, can even cause blindness.
Prof Dasgupta is conducting a international study to find a way to make diagnosis clearer and simpler.
He said: "It generally affects those over 50. It is quite prevalent in this area, but that is due to the percentage of elderly people we have living here.
"PMR is characterised by its abrupt onset of severe pain in the shoulders and hips. A blood test will show a high inflammation response in the patient."
PMR affects around three in every 10,000 people aged 50-plus in the UK every year. Men and women can both get PMR, though it is three times more common in women.
Although PMR and GCA can't be prevented, the symptoms can be controlled with steroid medication and often patients will make a full recovery within two years.
Prof Dasgupta said: "The two are related conditions and other than asthma, they are the commonest cause for steroids being prescribed in the community."
However the treatment itself is not without side-effects.
Complications can include hip and spine fractures, diabetes, high blood pressure, cataracts, skin problems and weight gain.
For that reason, Prof Dasgupta and rheumatology research nurse Jane Hollywood have now set up a local support group for sufferers.
The group's second meeting took place on Tuesday at Crowstone Church, Kings Road, Westcliff.
It aims to help raise awareness of the complaint and encourage patients to understand and manage their own health.
"Because there can be complications with the treatment, we have to look to maintain a balance between the benefit it brings to the health of the patient and any negative results," explained Prof Dasgupta.
"It is important the situation is assessed regularly. The support group will help to build a relationship between the medical professionals and patients."
Initially the group is working locally, though Prof Dasgupta's eventual aim is to set up a national network.
"There is a great need to increase the awareness of PMR and GCA," he added.
"We need to arrange help and support for patients who develop the groups."
The support group can be contacted via Jane Hollywood, on 01702 435347.