Fulham signed Knight from Rushall Olympic on a free transfer in 1999. As Knight was not a professionally contracted player to Olympic, Fulham were not obliged to pay a fee for him, but owner Mohamed Al-Fayed sent the club 30 tracksuits as a gesture of thanks. After five years at Fulham, Knight signed a contract extension that will keep him until 2008 after having established himself under Chris Coleman's management.
Knight scored four goals for Fulham, two in the 2004–05 season and two in the 2006–07 season. The first in a FA Cup match against Watford in a 1–1 draw, his second a Premier League goal against Norwich City in a 6–0 win. His last goal for Fulham came against Bolton Wanderers in a 2–1 loss. He was arguably Fulham's most consistent player in the 2006–07 season, a reward for this being given temporary captaincy of the club while regular skipper Luís Boa Morte was out injured.
Before the game against West Ham United that season it was announced that he had broken his jaw in two places while messing around with his brother. Chris Coleman has been quoted as saying that it takes more than horseplay to break one's jaw in two places, but Knight insists there was "nothing sinister" about the incident.
At the start of the 2007-08 season, Knight signed a two-year contract extension with Fulham, which will keep him until the end of the 2009/10 season. Prior signing a new contract, Knight was linked with a move away from Fulham, but insisted he want to stay at the club and achieved to win trophies. However, Knight would eventually leave for Aston Villa.
On 29 August 2007, Knight signed a four-year contract deal with the club he supported as a boy, Aston Villa, in a £3.5 million deal. Ironically his last Fulham match was the 2–1 defeat against Villa, in which he played a part in Villa's equaliser when an Ashley Young shot deflected off him into the net, although this was later given as Young's goal. In the early hours of the day of his transfer (29 August), Knight and his brother Carlos, were arrested in a drugs raid on the family home. Knight was released on police bail while Carlos was remanded in custody. Police said that a quantity of drugs were seized at the home. Knight feared that he may miss the press conference announcing his signing but his agent bailed him out and no mention of the incident was made at the press conference. Knight scored a headed goal on his Villa debut in a 2–0 win against Chelsea on 2 September 2007. Knight's next goal for Villa did not come until the following season, on 26 December 2008 when Villa were trailing 2–1 against Arsenal at Villa Park. Knight scored the equaliser in the 91st minute of the game in front of the Holte End to make it 2–2.
On 25 July 2009, Knight signed a three-year contract with Bolton Wanderers for an undisclosed fee believed to be in the region of £4 million.
Knight made his Bolton debut in the 1–0 reverse against Sunderland on 15 August 2009. He scored his first goal for Bolton against Wolverhampton Wanderers at the Reebok Stadium on 27 February 2010 and this led to a crucial 1–0 home win which lifted the side out of the relegation zone. He made his hundredth appearance for Bolton in their 3–0 defeat at Manchester United on 14 January 2012.
Knight's contract expired at the end of the 2011–12 season, making him a free agent. However, on 9th July, Coyle announced that he had signed a further two year contract.
Knight often took the captain's armband at Bolton when usual skipper Kevin Davies was off the pitch. When Davies left at the end of the 2012/13 season, Knight was named as the new captain for the 2013/14 season. Jay Spearing took the armband when Knight came out of the team and Spearing retaned it when Knight returned to the team.
On 8 March 2014, Knight scored his first goal in three and a half years when scoring Bolton's third in their 5-1 victory over Leeds United at Elland Road. At the end of that season he was released by the club along with Chris Eagles, Tyrone Mears and Jay Lynch.
Knight made his England debut on 28 May 2005 as a substitute against the United States in a friendly match. He gained his second cap in a friendly against Colombia on 31 May.
Personally I thought he was crap before we signed him and crap throughout his stay with us. Coyle's decission to give him an extra two years with us beggared belief - thanks Owen.
Anyway he's gone now so at least Freedman can't bring him on with 30 odd minutes left, at home, to go to five at the back, to defend a one goal lead against some shit team like Blackpool or Millwall anymore!