Karpus was elected captain of the 1921 basketball team. As a senior during the 1920–21 academic year, Karpus was once again declared academically ineligible in the fall. However, his eligibility was restored in December, allowing him to participate in most of the basketball season. Despite missing several games, Karpus, playing at the forward position, was the team's high scorer for the second straight year, and he led the team from a last place finish the prior year to a three-way tie for the Big Ten Conference basketball championship. The 1921 basketball team compiled a record of 16–4 and won both games against Michigan Agricultural for the first time in the history of the rivalry. In a summary of the 1921 basketball season, the University of Michigan yearbook praised Karpus' contributions: In any consideration of the players on the 1921 Varsity, Captain Joe Karpus leads, because of his high scoring ability, and the spirit which he put into the team. Karpus was the leading scorer of the team, both this year and last. He also ranked high in the Conference. It was his foul shooting that pulled more than one game out of the fire, during 1921. His performance in the first Illinois game, when he threw nine fouls out of a possible eleven will stand out as one of the most brilliant individual records of the season. Karpus coupled to his basket shooting ability an uncanny knack at dribbling. Karpus also played third base for the 1921 baseball team. The 1921 Michiganensian noted of Karpus: "When a hit was needed in a pinch, Coach Fisher could usually count on Joe who handled third base in a remarkable fashion. It was Karpus' third year on the Varsity." Minor league baseball After graduating from Michigan, Karpus played minor league baseball in the Michigan–Ontario League for the Bay City Wolves in 1921, the Saginaw Aces in 1922 and the Kalamazoo Celery Pickers in 1923. He maintained a .326 batting average and a .439 slugging percentage in 37 games for the 1921 Bay City team. Later years At the time of the 1930 Census, Karpus was living in Detroit, Michigan with his wife, Angeline "Angela" (Superzynski) Karpus. He listed his occupation at the time as mechanical engineer at a copper and brass manufacturer. From approximately 1937 to 1967, Karpus was employed by the Michigan State Highway Commission in Lansing, Michigan, the last 20 years