West Ham have slipped to second bottom of the table after a poor run of results that has coincided with injuries to several of their most experienced defenders.
The 30-year-old Johnson won the League Cup with Birmingham City in 2011 and helped Cardiff City reach the FA Cup final in 2008.
He joined Wolves in 2011 for a reported fee of 7 million pounds ($11.5 million) and made 42 Championship (second-tier) appearances for them last season before moving to Sheffield Wednesday on loan.
Johnson could go straight into the West Ham squad for Wednesday's League Cup semi-final first leg at Manchester City.
($1 = 0.6094 British pounds)
(Writing by Ed Osmond, editing by Pritha Sarkar)
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