Lainton came through the Academy at Bolton Wanderers, and began the 2009–10 season as the club's first choice goalkeeper in the Premier Reserve League under coach Alan Cork.

[12] After recovering from his injury, Lainton struggled to make a return to the first-team after being dislodged by newly signed goalkeeper Brian Jensen.

[13] Lainton remained as a second-choice goalkeeper at Bury until 8 February 2014, when he joined divisional rivals Burton Albion on a one-month loan to fill in for injured custodian Dean Lyness; he kept a clean sheet on his debut in a 1–0 victory at Morecambe later that same day.

[14][15] However, ten days later he punched a high ball into his own net to gift Rochdale the equaliser in a 1–1 draw at Spotland; manager Gary Rowett backed Lainton, saying "we write it off and move on".

[17] Lainton remained the first choice goalkeeper at the Pirelli Stadium, making fourteen appearances until he came off as a substitute at half-time after dislocating his thumb during a 1–0 defeat to Northampton Town on 12 April.

[23] He began the 2015–16 season in excellent form after taking over from the injured Christian Walton, and was named in the Football League Team of the Week after making "a number of superb stops" in a 1–0 win at Colchester United on 3 October.

[28] He was however, re-signed on a pay-as-you-play deal by Chris Brass in December, and was described as looking "surprisingly sharp" as he kept a clean sheet in a 0–0 draw at Fleetwood Town on Boxing day.

[31] On 7 April 2017, he joined Gary Johnson's Cheltenham Town on a seven-day emergency loan deal, as Calum Kitscha was injured and loanee Scott Brown was unavailable to play against his parent club Wycombe Wanderers.

[34] He started the 2017–18 season as the club's first choice goalkeeper, but had to be taken off with a thigh injury at half-time during the opening round of the EFL Cup and was ruled out of action for four weeks.

[40][41] On 6 July 2018, Lainton signed for National League side Wrexham on a season-long loan, where he was expected to compete with Christian Dibble for the first-team spot.

[42] He made his debut for Sam Ricketts's "Dragons" on the opening day of the 2018–19 season, and kept a clean sheet after saving a penalty from Inih Effiong during a 1–0 victory at Dover Athletic.

[60] Speaking in May 2010, Bolton Wanderers reserve team manager John Henry described Lainton as "an infectious character and a real grafter", "a good all-round keeper... a great shot-stopper and kicks well".