A higher number of previous hamstring injuries ( adjusted OR ( AOR ) 1.33 ; 95 % CI 1.11 to 1.61 ) , more degrees of active knee extension deficit after RTP ( AOR 1.13 ; 95 % CI 1.03 to 1.25 ) , isometric knee flexion force deficit at 15 after RTP ( AOR 1.04 ; 95 % CI 1.01 to 1.07 ) and presence of localised discomfort on hamstring palpation after RTP ( AOR 3.95 ; 95 % CI 1.38 to 11.37 ) were significant independent predictors of re-injury .