1. when visible knees (or sometimes legs) are of a distinctly different color to the rest of the body. usually from when tanning of the legs is done separately from the upper body.
2. to describe someone with jaffa knees (said quickly as one word, like "Japanese")
The use of 'Jaffa' is borrowed from the Jaffa chocolates - chocolate confectionery with an orange candy shell - describing the either particularly orange tan, or even dark brown (almost chocolate) color of the said knees
Fred: Hey, did you see that girl? Her knees were like, brown!
Ulric: She's got Jaffa knees.
A condition brought on by military service where the knees hurt beyond what would be considered normal. Usually, the Department of Veterans affairs will deny the existence of the condition so that they can deny paying the veteran compensation. Any injury or aggravation made worse by military service.
My classmate Derrick D. says he suffers from Army Knees and it is difficult for him to sit or stand for prolonged periods because he was a paratrooper.
My knees are in terrible shape because we ran in boots when I joined the Army.