When the Knicks staged training camp in late September, there were a handful of sessions open to families of players and staff. It was a new concept for the Knicks — gleaned from one of sports’ model franchises, the Pittsburgh Steelers.

According to sources, Knicks president Steve Mills and new general manager Scott Perry attended Steelers training camp Aug. 5-6 to get a behind-the-scenes look at the squad with the most Super Bowl victories (six) in NFL history.

Perry has attended Steelers training camp for about five years to closely watch their operation, becoming friends with longtime head coach Mike Tomlin and GM Kevin Colbert.

“I’m so excited and happy for Scott and the New York Knicks,’’ Tomlin said in a statement to The Post. “Scott is a quality man and a quality professional.

“We spent a lot of time together over the years. It’s just been a great relationship being able to talk about leadership, leadership styles, and some of the different challenges that different sports present but also the parallels. I like his approach to business. He’s a detailed and thoughtful leader. I expect those guys to be extremely successful.”

Perry, 53, is part of the Steelers’ extended family — his father, Lowell, was a Steelers’ draft pick and later became Pittsburgh’s receivers coach in the late ’50s.

After being hired in July one of the first things Perry wanted to do with Mills was bring him to Steelers camp, according to a source.

“Scott looks at Pittsburgh as one of the best in professional sports because they know who they are as an organization,’’ said an associate of both Mills and Perry. “It may have the strongest culture in his eyes because they know what they want in the makeup of a player — the skill set and mindset — and it’s consistent.’’

The associate said Perry also has been intrigued with the Steelers’ preparation for the draft and how they handle much more personnel than an NBA organization. Perry, who acknowledged at his introductory press conference to being a proud fan of Steeler Nation, declined to comment for the story because it involved the inner workings of another franchise.

Mills, according to the associate, got a lot out of watching the Steelers up close, seeing their stability. Colbert has been GM since 2000 and Tomlin is in his 10th year as head coach.

“I think Steve got a sense the players, coaches and front office were very connected — and a lot of that stems from how long they’ve been together,’’ the associate said. “He also found a high level of accountability from the coaching staff to the players — which was very impressive. All of the coaches/players being accountable to how they want to play and what they can consistently expect from each other.’’

Scott Perry is extremely proud of his pioneering father’s story. Lowell, a receiver out of Michigan, suffered a career-ending fractured pelvis/hip on a hard hit by Giants star defensive tackle Rosey Grier late in his record-setting rookie year. For 13 weeks, Steelers owner Art Rooney Sr. or his wife reportedly visited or called each day.

Perry’s ideology of creating strong bridges between players and management — especially after the Phil Jackson fiasco — comes partly from the Steelers’ philosophy, according to the associate, and the Pistons, for whom he toiled seven seasons.

Former Pistons GM Joe Dumars said in an email to The Post: “[Perry] understands that you have to reach the person before you reach the player.”