Katranis made his professional debut in the Super League for Atromitos on 25 September 2016 in a game against Asteras Tripolis. According to "footballscout24.it" website, was the only Greek player to feature on a list entitled “TOP 40 young talent in world football – born in 1998″.
In August 2017, Ligue 1 side Saint-Étienne announced the signing of Katranis on a five-year contract. The transfer fee paid to Atromitos was reported as €800,000 plus as 15% re-sale clause in case of a future transfer. He didn't play a single game with the first team as the jump of 14 games in the Super League, in a mid-table club, in a top French club as Saint-Étienne, is a very big gap.
Loan to Royal Mouscron
On 21 June 2018, he signed a long season contract with Belgian club Royal Excel Mouscron on loan from Saint-Étienne. At the end of the first round, it seems that it is not counted by the coach and former of the Olympiacos U21 team, Bernd Storck, for the second half of the season. After 8 appearances and 1 in the Belgian Cup, the young defender is expected to return to France. As Foot Sur 7 reported, the 20-year-old left-back has no place in Royal Excel Mouscron and will return to St-Etienne despite the fact that the coach Jean-Louis Gasset, who did not trust Katranis at the beginning of the season and preferred to gave him as a loanee.
Loan to Atromitos
On 22 January 2019, the return of the young international to Atromitos was officially finalized for a year and a half with a buy out option, while Katranis is intended as a replacement for Dimitris Giannoulis who returned to PAOK. On 1 August 2019, Atromitos reached the UEFA Europa League third qualifying roundthanks to a thrilling 3–2 home win over Dunajska Streda at the Peristeri Stadium which gave the Athens club a 5–3 aggregate success. Katranis opened the score, as he picked up possession on the edge of the penalty area after the ball had deflected into his path. The 21-year-old defender showed great skill and turn of pace to skip past a couple of Dunajska challenges before slotting the ball confidently passed Martin Jedlička in the visiting goal. It was his first goal in European club competitions.
