All muscles and masochism, blood and brutality, Stallone proves as always he can take it as well as dish it out, but this is never anything more than an assembly-by-numbers exercise, geared to his standard brand of sleeveless integrity. With its sombre, predominantly grey-and-white visual style, the film does well by its real prison locations (Rahway prison, East Jersey), but the drama in general and Sutherlands character in particular stay cardboard and paste.
The plot, falling over itself to keep Sly free of any taint of criminality (the escape was to see his dying stepdad, the sentence for beating up some burglars), at the same time pads out its paper-thin premise with a couple of variations on the old Rocky stand-bys: The Training Sequence and The Match. Lock Up is hardly impressive, but it does pass the time pardonably well. And, with a big electric chair confrontation at the end, it has the good sense to keep its funniest and most exciting scene till the last.