[1] He also played three seasons at UCLA in college tennis, where he earned All-American honours in both singles and doubles before turning pro in 1992.

Their quarterfinal match against Sweden's Simon Aspelin and Australian Todd Perry lasted 6 hours and 9 minutes, with Knowles and Nestor eventually winning 5–7, 6–3, 6–7(5–7), 6–2, 23–21.

After reaching the Basel final with James Blake, Knowles reunited with Nestor once again to win the 2007 Tennis Masters Cup.

[3] Knowles then played with fellow Grand Slam doubles champion Mahesh Bhupathi, for two seasons in 2008 and 2009, and the two were one of the most successful teams on tour, qualifying for the season-ending championships in both years.

In 2010, Knowles joined forces with Fish, and after both struggled with injuries the first half of the season, the two captured the Legg Mason Tennis Classic in Washington, defeating Tomáš Berdych and Radek Štěpánek in the final.

Prior to that, the two made semifinal appearances in San Jose and Memphis and the quarterfinals of the BNP Paribas Open at Indian Wells.

After falling in the first round of Wimbledon with Łukasz Kubot, Knowles played his 10th season of World TeamTennis with the Sacramento Capitals, and then partnered Xavier Malisse to the Farmers Classic title at his former college campus, UCLA.

In October, Knowles was invited to participate in the 19th annual World TeamTennis Smash Hits charity event in Cleveland, co-hosted by Sir Elton John and Billie Jean King.

In 2014, he partnered Ryan Harrison and made the finals but lost to top seed Sam Groth and Chris Guccione in straight sets.

The last tournament of his career was the 2016 Irving Tennis Classic where he partnered Benjamin Becker but lost in the first round to Jason Jung and Jakob Sude in straight sets.

Representing the Bahamas, Knowles competed in five consecutive Olympic Games (1992-2008) and is his country's all-time leader in Davis Cup wins, playing in 29 ties.

He received the prestigious Davis Cup Commitment Award from ITF president Francesco Ricci Bitti at the All England Club in 2014.

Since 2013, Knowles has worked on-air for American TV Tennis Channel, providing in-match commentary, courtside interviews and tournament desk analysis.