The Relationship Between Anterior-Posterior Knee Laxity and the Structural Properties of the Patellar Tendon Graft

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Abstract
We studied the relationship between anterior-posterior knee laxity and the structural properties of autogenous patellar tendon grafts used to replace the anterior cru ciate ligaments in dogs 1 year after reconstruction. At 30° (full extension for the dog), 60°, and 90° of flexion a significant inverse correlation was found between anterior-posterior knee laxity and the ultimate failure strength of the graft. Likewise, at 60° and 90° of flexion a significant inverse correlation was found between knee laxity and the linear stiffness of the graft. In all cases, as knee laxity increased, the ultimate failure load and linear stiffness values of the graft were found to decrease. There was also a significant increase in anterior-posterior knee laxity of the reconstructed knees (produced by an increase in anterior translation of the tibia relative to the femur) compared with the contralat eral control knee. The group of dogs that underwent a sham operation without reconstruction of the anterior cruciate ligament had no change in anterior-posterior knee laxity or the structural properties of the anterior cruciate ligament. The clinical significance of this in vestigation is that knee laxity measurements demon strating an increase in anterior translation of the tibia relative to the femur during graft healing may indicate that the graft has weakened and reduced structural properties.