The singer has revealed she is undergoing physiotherapy in the hope of it getting better in time for the weekend.
Sophie Ellis-Bextor and dance partner Brendan Cole
She told The Sun: "My knee really hurts. I had to have physio on it three times last week.
"I hope I can go one more week. I’m sure I will because I’m enjoying myself so much."
Meanwhile, the song list and dance styles the couples will be taking on have been revealed.
Susanna, Abbey, Sophie and Natalie will now battle it out in the final
Sophie Ellis-Bextor and Brendan Cole will perform the Viennese Waltz to 'My Favourite Things' by Julie Andrews (judges' choice); 'I Wanna Dance with Somebody' by Whitney Houston (showdance) and the Charleston to 'Rock It for Me' by Caravan Palace (couples' favourite).
Abbey Clancy and Aljaz Skorjanec will do the Waltz to 'Kissing You' by Des'ree (judges' choice); 'Sweet Child o' Mine' by Guns N' Roses (showdance) and the Quickstep to Katrina and the Waves' 'Walking on Sunshine' (couples' favourite).
Susanna Reid and Kevin Clifton will dance their Quickstep to Tommy Steele's 'Good Morning' (judges' choice); 'Your Song' by Ewan McGregor (showdance) and Paso Doble to Carmen's 'Los Toreadors' (couples' favourite).
And Natalie Gumede and Artem Chigvintsev will perform their Cha Cha to Boney M's 'Rasputin' (judges' choice); 'Steppin' Out With My Baby' by Christina Aguilera and Tony Bennett (showdance) and the American Smooth to Jennifer Hudson's 'And I'm Telling You, I'm Not Going' (couples' favourite).
The 'Strictly Come Dancing' final airs on Saturday at 6.30pm on BBC One.
Series 1 / 2004 Winner: Natasha Kaplinsky Partner: Brendan Cole Also Starring: Jason Wood, David Dickinson, Verona Joseph, Claire Sweeney, Martin Offiah, Lesley Garrett, Christopher Parker
Series 2 / 2004 Winner: Jill Halfpenny Partner: Darren Bennett Also Starring: Quentin Wilson, Carol Vorderman, Esther Rantzen, Diarmuid Gavin, Sarah Manners, Roger Black, Aled Jones, Julian Clary, Denise Lewis
Series 3 / 2005 Winner: Darren Gough Partner: Lilia Kopylova Also Starring: Siobhan Hayes, Jaye Jacobs, Gloria Hunniford, Fiona Phillips, Dennis Taylor, Will Thorp, Bill Turnbull, Patsy Palmer, James Martin, Zoe Ball, Colin Jackson
Series 4 / 2006 Winner: Mark Ramprakash Partner: Karen Hardy Also Starring: Nicholas Owen, Jimmy Tarbuck, Mica Paris, DJ Spoony, Georgina Bouzova, Jan Ravens, Ray Fearon, Peter Schmeichel, Claire King, Carol Smillie, Louisa Lytton , Emma Bunton, Matt Dawson
Series 5 / 2007 Winner: Alesha Dixon Partner: Matthew Cutler Also Starring: Brian Capron, Stephanie Beacham, Willie Thorne, Gabby Logan, Dominic Littlewood, Penny Lancaster Stewart, Kate Garraway, John Barnes, Kelly Brook, Kenny Logan, Letitia Dean, Gethin Jones, Matt Di Angelo
Series 6 / 2008 Winner: Tom Chambers Partner: Camilla Dallerup Also Starring: Phil Daniels, Gillian Taylforth, Gary Rhodes, Jessie Wallace, Don Warrington, Mark Foster, Andrew Castle, Heather Small, Cherie Lunghi, John Sergeant, Jodie Kidd, Christine Bleakley, Austin Healey, Lisa Snowdon, Rachel Stevens
Series 7 / 2009 Winner: Chris Hollins Partner: Ola Jordan Also Starring: Martina Higgins, Richard Dunwoody, Rav Wilding, Lynda Bellingham, Joe Calzaghe, Jo Wood, Zoe Lucker, Craig Kelly, Phil Tufnell, Jade Johnson, Ricky Groves, Natalie Cassidy, Laila Rouass, Ali Bastian, Ricky Whittle
Series 8 / 2010 Winner: Kara Tointon Partner: Artem Chigvintsev Also Starring: Goldie, Paul Daniels, Peter Shilton, Tina O'Brien, Jimi Mistry, Michelle Williams, Felicity Kendal, Patsy Kensit, Ann Widdecombe, Gavin Henson, Scott Maslen, Pamela Stephenson, Matt Baker
Series 9 / 2011 Winner: Harry Judd Partner: Aliona Vilani Also Starring: Edwina Currie, Dan Lobb, Rory Bremner, Nancy Dell'Olio, Lulu, Audley Harrison, Russell Grant, Anita Dobson, Robbie Savage, Alex Jones, Holly Valance, Jason Donovan, Chelsee Healey
Series 10 / 2012 Winner: Louis Smith Partner: Flavia Cacace Also Starring: Johnny Ball, Jerry Hall, Sid Owen, Colin Salmon, Fern Britton, Richard Arnold, Victoria Pendleton, Michael Vaughan, Nicky Byrne, Lisa Riley, Dani Harmer, Denise van Outen, Kimberley Walsh