Nigerian sensation Yakubu Aiyegbeni scored his eighth goal of the season which looked to have given Pompey their first win at Deepdale in 30 years but McKenna popped up to spoil the party for Harry Redknapp's men.
Micky Adams' Leicester City side cut Portsmouth's lead to just three points look as they beat Gary McAllister's Coventry City side at 2-1 at Highfield Road.
Scottish international Billy McKinlay scored his first goal in a Foxes shirt when he scored a 30-yard screamer three minutes after the break before James Scowcroft doubled their lead on 68.
Loan striker Matt Jansen pulled a goal back seconds after coming on as a substitute when he headed home McAllister's corner with 20 minutes to go.
Michael Tonge scored a cracking goal for Sheffield United to keep the pressure up on second place Leicester City with a superb strike after 18 minutes as they ran out 2-0 winners over Derby County.
The Blades midfielder beat two defenders en route to scoring a superb goal from range, his first since January, that left Rams' shot stopper Lee Grant no chance before United's FA Cup hero Steve Kabba made it two.
Reading boss Alan Pardew will be pleased with the way his men battled to a 1-0 victory over Bradfor City after having Nathan Tyson sent off on 39 minutes for a second bookable offence.
Nicky Forster scored his 14th goal of the season on 66 minutes as The Royals continue their quest for The Premiership.
Nottingham Forest kept themselves in the frame for a play off place with a 4-0 win over Norwich City.
On-loan Darren Huckerby fired Paul Hart's men in front on 11 minutes before Marlon Harewood netted his 11th goal in 10 games and 19th in all 11 minutes later before Gareth Williams and Jim Brennan completed the rout.
Wolves were in scintillating form as they put Gillingham to the sword in a 6-0 mauling at Molineaux.
Nathan Blake opened their account after a quarter of an hour before Colin Cameron and Kenny Miller celebrated their call-ups to the Scotland squad with goals on 22 and 45 before Miller got his second on 48.
Republic of Ireland winger Mark Kennedy got the third goal on 37 minutes before making it five on the stroke of half time as Gillingham had a game they will want to forget.
Ipswich Town rescued a point against relegation haunted Brighton which may finally bring an end to their play off hopes.
Marcus Bent capitalised on a poor back pass from Seagulls defender Danny Cullip to slot past Dave Beasant for the first score before a Tony Rougier double looked like earning all three points for Steve Coppell's men.
Bent missed a second half penalty before Dutchman Martjin Reuser equalised for Town with minutes to spare.
Rotherham United boss Ronnie Moore will be pleased with the way his side bounced back from their midweek defeat to Grimsby Town with a 2-1 win over Wimbledon who were on the back of two straight wins.
Re-called Mark Robins continued where he left off for Bristol City with his sixth goal in nine games on 19 before giant defender Guy Branston made it two after the re-start and David Connoly scored a consolation for The Dons on 59 minutes.
Burnley boss Stan Ternant will be pleased with his side for ending their four game losing streak with a 1-1 draw against Grimsby Town.
Stuart Campbell put The Mariners ahead two minutes before the break before Alan Moore got on the end of a Steve Davis head down to level things seven minutes into the second half.
Crystal Palace beat lowly Walsall thanks to the cool head of Dougie Freedman and Wayne Routledge.
Scotland star Freedman stroked home a decisive penalty on 33 minutes while Carl Robinson and Martin O'Connor were red carded in the second half for violent conduct before Routledge added a second on full time to record Palace's first home win in eight games.
Former Dutch international Peter Hoekstra notched a brace to keep alive Stoke City chances of avoiding the drop thanks to their 2-1 victory at Watford.
Hoekstra scored his first from the spot 10 minutes before half time and then notched his fifth of the season on 49 before Heidar Helguson scored a consolation goal with 20 minutes to go.
Millwall returned to winning ways with a 3-0 win at the New Den over bottom club Sheffield Wednesday.
The Owls lost further ground on the other teams around them when Steve Reid scored two goals in three minutes in the first half before Paul Ifill made it three on 54.
For full Division One round-up :
Bradford City 0-1 Reading
Burnley 1-1 Grimsby Town
Coventry City 1-2 Leicester City
Crystal Palace 2-0 Walsall
Ipswich Town 2-2 Brighton & Hove Albion
Millwall 3-0 Sheffield Wednesday
Nottingham Forest 4-0 Norwich City
Preston North End 1-1 Portsmouth
Rotherham United 2-1 Wimbledon
Sheffield United 2-0 Derby County
Watford 1-2 Stoke City
Wolverhampton Wanderers 6-0 Gillingham
For Division One league table - click here
