Sarah Lister suffers from Genuphobia, making trips to the beach, nights out with friends or watching her fiancé Chris Bayliss playing football an ordeal.

Miss Lister, 25, from Gosport, Hants, said: "In the summer it is worse because I don't feel like I can go to the beach or go to the pub.

"I worry that if I saw someone in a bathing costume or a short skirt I would just freak out.

"I quiver in fear if anybody tries to touch my knees, or accidentally bumps into them.

"I am fine with my fiancé, my immediate family and a select group of friends, but strangers' knees still hold a lot of fear for me.

"Even the thought of other people's knees makes me feel very uneasy."

Her phobia began as an 11-year-old schoolgirl when she saw her father dislocate his knee after a freak fall at their home.

Since the traumatic incident, she has tried a cocktail of quirky treatments, including hypnotherapy, to help ease her panic.

Charity Anxiety UK, which deals with phobias and other disorders, said: "An estimated 13 per cent of the population will develop a phobia at some point in their lives.

"One of the most effective ways to deal with anxiety disorders or phobias is to understand it.

"There are a number of ways forward in terms of treatment of anxiety disorders and getting help including; services through the NHS, psychological interventions, medication and self-help groups.

"Always consult your GP to obtain a diagnosis if you suspect you are suffering from an anxiety disorder.

"Self-diagnosis is not an effective way as misdiagnosis could lead to the wrong treatment being administered which can set the sufferer back even further."