“Personally, I think knees should be kept for the eighth or ninth date, or the wedding day. As a nice surprise you know? 'oh, my darling, you have knees! I never would have thought”

The Last Lecture (2008)

Oh! Susanna, W.C. Peters & Co. (1848).
Context: Oh I come from Alabama with a banjo on my knee,
I'm going to Louisiana, my true love for to see
It rained all night the day I left, the weather it was dry
The sun so hot I froze to death; Susanna, don't you cry.
Oh, Susanna, don't you cry for me
For I come from Alabama,
With my banjo on my knee.

"Pope Francis’ answer for his bad knee? Tequila" https://www.pbs.org/newshour/world/pope-francis-answer-for-his-bad-knee-tequila, PBS, May 17 2022
2020s, 2022

Source: Daring to Dream

Reported by Paul Scott in the Lewiston Daily Sun (27 September 1972) again as remarks at Duke University; http://news.google.com/newspapers?id=FXwgAAAAIBAJ&sjid=7mcFAAAAIBAJ&pg=1010,3814989 reported elsewhere as a remark made at Michigan State University (22 November 1970) and cited to the Detroit Free Press but without a date, page or headline.
Rick Perlstein, in a 2005 London Review of Books article and in his 2008 book Nixonland: The Rise of a President and the Fracturing of America (Simon and Schuster, p517 http://books.google.com/books?id=dM_enWzoghoC&pg=PA517#v=onepage&q&f=false), accused Helms of inventing the quote: "They tapped their network of friendly media propagandists, like the future Senator Jesse Helms, then a TV editorialist, who supplied an invented quotation that still circulates as part of the Fonda cult’s liturgy." http://www.lrb.co.uk/v27/n22/rick-perlstein/operation-barbarella The COINTELPRO Papers (2002) documents a separate attempt to plant false quotes from Fonda in the press.
Disputed

Source: Death's Mistress

Fire from Heaven (1969)