McKnight attended Apopka High School, where he lettered in football, basketball and track.
He accepted a scholarship to play for Liberty University under former NFL head coach Sam Rutigliano. He was forced to sit out his freshman season, however, due to the NCAA's Proposition 48 regulation.
He became a starter as a junior, registering 50 receptions for 711 yards and 5 touchdowns. In his last year he had 39 receptions for 812 yards and 8 touchdowns. He finished his college career with 144 receptions for 1,948 yards and 17 touchdowns.
McKnight was signed by the Seattle Seahawks as an undrafted free agent after the 1994 NFL Draft. He spent the first ten games of the season on the practice squad before being activated on November 19. In 1995, he registered 14 special teams tackles. The next year, he was second on the team with 25 special teams tackles.
He slowly developed into a deep threat at wide receiver, starting 6 games in 1997, while registering 34 receptions for 637 yards and 6 touchdowns, after missing the first 4 games with a sprained knee suffered in the preseason.
On June 24, 1999, he was traded to the Dallas Cowboys in exchange for a third round draft choice (#80-Darrell Jackson).
McKnight spent the 1999 season on the injured reserve list, after tearing the anterior cruciate ligament in his left knee during training camp. The next year, he became the team's leading receiver after Joey Galloway was lost for the season, registering 52 receptions for 926 yards. He also had to adjust while playing with 3 different quarterbacks (Troy Aikman, Randall Cunningham and Anthony Wright).
On March 16, 2001, he signed as a free agent with the Miami Dolphins, reuniting with offensive coordinator Chan Gailey, who was his head coach with the Dallas Cowboys. After starting in his first season with the team, he was later relegated to a reserve role when Oronde Gadsden passed him on the depth chart. He was released on March 2, 2004.
On May 20, 2004, he was signed by the New York Giants. He was placed on the injured reserve list after being sidelined with a turf toe injury since early in training camp. He wasn't re-signed at the end of the season.
McKnight worked as a financial services advisor. He currently coaches the Cypress Bay High School wide receivers and track. He is the father of David McKnight, who currently plays running back at Tiffin University.