McDavid Jumper's Knee The McDavid™ Jumper's Knee Strap helps reduce pain caused by patellar tendonitis (jumper’s knee/runner’s knee and Osgood-Schlatter disease. VELCRO® brand fastener adds graduated compression of the patellar tendon. Non-slip semi tubular buttress helps relieve pain. Sold individually. Sz: One size fits most.