Trivia

Director John Flynn has said of this movie, in a 2005 interview with Harvey F. Chartrand for Shock Cinema: "Lock Up (1989) is a strange lesson in how Hollywood movies are made. Stallone had a 'window' which means the guy was available for a certain window of time. Larry Gordon [Lawrence Gordon] had a terrible script set in a prison. Stallone calls James Woods and asks if I'm any good as a director. Woods says yeah, he's a good director and you ought to work with him. So we have a director and a star, but no script. All we have is a theme - a guy escaping from prison. So we hire Jeb Stuart, who was then one of the hottest writers in Hollywood, to rewrite the script and we go off looking for prison locations. Now we have a star, a theme, a shooting date, a budget, a studio, but we still have no script. So we all go back to New York City, and move into a hotel where Larry 'tortures' Jeb and Henry Rosenbaum into writing a script in record time. Meanwhile, I'm going around scouting prisons. We finally found one in Rahway, New Jersey. Jeb and Henry were writing the script as we were making the movie. New pages would come in every day. There was one day when I was on the third tier of a cell-block in Rahway Penitentiary and I had nothing to shoot. I had my movie star, all these extras and a great location - and the pages were on their way. So we sat around and bullshitted with the prisoners. Stallone is a smart guy and a very underrated actor. If I ever needed a better line, he'd come up with one. Stallone is a really hard worker. I had no problem whatsoever with him".

Chuck Wepner, the real-life inspiration for Rocky (1976), was an inmate at the prison where the film was shot. Sylvester Stallone greeted Wepner and told the other inmates that Wepner was "the real Rocky".

The cast includes real inmates of Rahway State Prison, which is also known as East Jersey State Prison, and is located in Rahway, New Jersey. Some of the prisoners appear as extras and background artists in the movie.

Sylvester Stallone gave Tom Sizemore his first real break in this film. Their friendship lasted to his dying day.

Sylvester Stallone originally created a character named "Chink Weber" for Rocky II (1979) who was to be played by Chuck Wepner. But the character was deleted from the script. Stallone reused the "Chink Weber" name for the script for this film with the part being played by Sonny Landham.