Former Newcastle Knights' outside back Jake Mamo has called it quits effective immediately, retiring from rugby league after a series of head knocks and injuries.

The Central Coast-born Mamo played 29 NRL games between 2014 and 2016 for Newcastle, enjoying some personal form, however, it wasn't replicated as team success during his time at the club.

The winger-turned-fullback won just four of his 29 NRL games, a strike rate of under 14%, including losing his last 15 consecutive games in first-grade before switching to the Super League.

Despite heading into his seventh season in England, Mamo has only recently brought up the 100 Super League games milestone due to repeated injuries and head knocks, never playing more than 16 games in a season.

The 28-year-old blamed injuries for his retirement, and was thankful for all that the code had done for him over the years.

"There were a lot of factors that came into the decision. The main one being I've suffered too many head knocks and injuries," Mamo said in a club statement.

"I suffered a bad back injury in my last game ... and I couldn't move for three days. I thought ... I never want to feel like that ever again.

"Rugby league has given me a lot and ... the chance to move over here to the UK.

"I've had good relationships with fans at all the clubs I've been at and that is going to be the thing I miss the most."

He's split his time in England playing for Huddersfield, Warrington and now Castleford, and came off the bench for the Wolves in their 18-4 win over St Helens in the 2019 Challenge Cup final.

Mamo amassed over 50 tries during his English stint and is expected to return to Australia now that his playing days are over.