Rookie Leinster second-row Charlie Ryan has been forced to retire at the age of 23 with 'immediate effect.'

The 6-foot-7, 115-kilogram lock is retiring 'due to a longstanding and recurring knee injury,' the province said.

Ryan, who was captain of the Grand Slam-winning Ireland U20s side of 2019, captained Leinster Rugby A to its win over Ulster A in the 2019 Celtic Cup final.

"I finish my career deeply grateful to Leinster Rugby," Ryan said. "Firstly, to Leo and the coaching staff for showing belief in me as a person and player, despite my injury struggle. The signing of a senior contract with my boyhood club was one of my proudest moments. There's nothing more the club could have done for me with respect to this injury.

"I leave the club at peace mentally due to the tireless work of the medical team. Every possible avenue to success was explored.

"There are a countless number of coaches and mentors I will thank personally over the coming days for the help I received to get here.

"I loved playing the game. I'm so incredibly lucky to have got the opportunity to play it. I don't regret one second of the journey. I have made connections with some incredible people that will last a lifetime. I could not have gotten to this point without the endless support from my family and friends. I am incredibly lucky to have had them there to help me. I wouldn't have got anywhere near where I am now, if it was not for their selfless support of me in my pursuit of this dream."

Leinster head coach Leo Cullen said: "Charlie has always been a player who has shown great leadership, and that was clearly displayed when he led the Ireland U20s to Grand Slam success back in 2019.

"Unfortunately, Charlie has had to battle ongoing knee issues in the time since then. Everyone who has worked with him over the last number of seasons are really saddened to hear that he is being forced to retire now from the game at such a young age.

"Having had the pleasure of working with Charlie over recent seasons, I am confident that Charlie will be a success with whatever he decides to do next, as he is incredibly diligent, is able to build strong connections with people and is a great teammate to be around.

"I think I can speak on behalf of everyone here at Leinster Rugby in wishing Charlie every success for what he turns his attention to next."