New York - The octogenarian artist is being sued over intellectual property rights to her latest line of geriatric sanitary wear by rival designers who allege plagiarism and, er, 'taking the piss'.
Ono's super-absorbent incontinence pads were launched last February in a swish Fifth Avenue boutique sponsored by the 70-somethings publisher GeriNutzMag.con.
At $100 for a packet of five the line looked pricey until Jane Fonda modeled a pair and sent sales rocketing through the roof.
This week a New York law suit claims Ono stole the copyright from its lawful owners after 'test driving' the pad in an emergency moment during an Oscars Night party back in 2010.
The diaper was subsequently rebranded and launched under Ono's 'Bladder Hell' range aimed at US seniors watching cable TV.
This week a New York judge will decide if Ono broke US copyright rules and, if so, how much damages must be paid to settle the suit.
Last week there were reports of a furious row between Ono and the 'Good Samaritan' who kindly lent her the Oscars Night diaper that eventually lead to this week's ugly court case.
Apparently Ms Ono returned the original pad after it gave her some temporary relief.
Joan Collins is 104.