Former Wales star Henson was ruled out for up to six weeks of the new season after undergoing surgery on Sunday following a first-minute challenge by Scarlets prop Manu in Saturday's pre-season friendly.
Aviva Premiership newcomers London Welsh were reportedly furious over the incident at the time but having reviewed a DVD of the match, they announced they were satisfied the clash was accidental.
The Exiles said in a statement: "London Welsh would like to confirm that it will not be taking any further action over the injury suffered by Gavin Henson in last Saturday's friendly with the Scarlets at Parc y Scarlets.
"Having reviewed the DVD, the club are satisfied that the injury to Gavin was caused by an accidental clash of heads and the club does not attach blame to any Scarlets player."
Henson's latest injury was another blow in the 30-year-old's bid to kick-start his career at both club and international level and also a major setback for London Welsh, who unveiled him as their marquee summer signing last month.
- Sports & Recreation
- London Welsh
- Gavin Henson