Failure of an ACL reconstruction can take different forms with graft stretching, graft failing to incorporate, traumatic re-rupture and infection being the most frequent causes. The assessment of ACL reconstruction failure can be performed in different ways. Samitier et al report the knee may demonstrate objective laxity (as tested by clinical tests such as Lachman and Pivot Shift or mechanical tests such as the KT1000). There may be a patient perception of instability even though objective tests are satisfactory). Using the KT1000 arthrometer, Alford and Bach report the rationale for a maximum manual side-to-side difference of 3 mm when assessing anterior tibial translation or an absolute laxity of 10 mm in the injured knee as the diagnostic criteria for ACL deficiency. Patient recorded outcome measures such as the Knee Osteo-arthritis Outcome Score (KOOS), Tegner activity scale and the International Knee Documentation Committee (IKDC) subjective questionnaire are all validated and can be used to assess satisfaction with surgical outcome and functional ability.