We were mountain biking in the Poulter Valley of Arthurs Pass National Park New Zealand when  I fell off my bike on steep rough ground. My knee received a deep puncture wound, with excruciating pain going up my inner leg to my groin. I was unable to bend the knee thus unable to continue riding the bike with  approximately 9km with some grunty Grade 3  to return back to our vehicle.  A second person had fallen off her bike an hour earlier and was unable to ride the bike but able to push it.   Considering the bigger picture, it was decided to request  help, luckily a passing biker had an ACR Resqlink.  The decision was not taken lightly as all members of our party are experienced outdoor people in a range of outdoor activities with a perfect safety record.