The Seahawks announced Knox's death Sunday morning, describing him as a "beloved figurehead by players, coaches and staff."
"His presence projected an external toughness, but merited instantaneous respect by the genuine care and concern he held for his players," the team said in a statement. "He was one of the great influences not only in football, but in life."
"He established a winning culture and a legacy that will never be forgotten, being the only coach to lead the Rams to five consecutive double-digit-win seasons," the Rams said in a statement. "The memories and accomplishments that Coach Knox left behind will continue to inspire us and Rams fans. We hold his family in our thoughts and prayers during this difficult time."
Knox compiled a record of 186-147-1 in 22 seasons with the Rams, Seahawks and Buffalo Bills. Nicknamed "Ground Chuck" due to his run-first offenses, Knox was named NFL Coach of the Year three times -- in 1973, 1980 and 1984.
Despite their regular season successes, Knox teams routinely came up short in the playoffs. The Rams, led by the "Fearsome Foursome" defensive line, lost three consecutive NFC Championship games between 1974 and 1976. After being fired by Rams owner Carroll Rosenblom, Knox spent five season in Buffalo. He led the Bills to two playoff appearances, but never got past the AFC divisional round.
Knox's best work may have been in Seattle, where the Seahawks had not made the playoffs since entering the NFL in 1976. In Knox's first season, the Seahawks earned a wild card spot, won their first playoff game over the Denver Broncos, then upset the Dan Marino-led Miami Dolphins to reach the AFC Championship Game. Knox's Super Bowl dreams ended there, as the Seahawks lost to the eventual champion Los Angeles Raiders.
In 1984, the Seahawks went 12-4, but couldn't beat out John Elway's Broncos for the AFC West title. They won their first playoff game, defeating the Raiders 13-7. But Marino and the Dolphins got their revenge in the divisional round, shredding the Seahawks 31-10.
After 1984, Knox coached seven more years in Seattle but only won 10 or more games once, in 1986. In 2005, Knox was inducted into the Seahawks Ring of Honor in recognition of his achievements with the franchise.
He returned to the Los Angeles Rams for the 1992 season, but couldn't replicate his earlier success. The Rams went a combined 15-33 in Knox's three seasons before the franchise moved to St. Louis.
A Pennsylvania native, Knox was a two-way tackle at Juniata College and served as a captain on the school's undefeated 1953 team. He began his coaching career as an assistant at Juniata. He was a high school assistant at Tyrone and then head coach at Ellwood City before moving on to Wake Forest and Kentucky.
Knox entered professional football in the AFL with the New York Jets as offensive line coach in 1963, and played a key role in the recruitment of quarterback Joe Namath. He remained with the Jets until 1966, and was then offensive line coach with the Detroit Lions from 1967-1972.
The Associated Press contributed to this report.