A poster in the doctors' waiting room

[SpawnOfObOb]

Was encouraging patients to attend a workshop and discover the "route cause" of their knee pain :o

[prism]

... which in many cases is an acute inflammation of the spelling gland...

[HangingGarden]

...or strain caused by changing gear on a particularly challenging road?

[blackeyedsusan]

Aound here it would be caused by walking and driving over the potholes!

[FuckerSnailInYourHedgerow]

Was the poster 'just sat there waiting'?