Evidence-based Sports Medicine

Evidence-based Sports Medicinestabilisers to lateral opening include the cruciate ligaments and theposterolateral capsule.The PCL is the primary restraint to posterior translation of the tibiain all degrees of flexion where it provides 94% of the restraining forceto posterior displacement. 36 The secondary restraints include theposterolateral capsule, popliteus complex and the medial collateral.Sectioning of the PCL alone produced an increase in straight posteriortranslation with no change in the rotation or varus and valgusrotation. 37 The maximum displacement was seen at 90. Therefore theposterior drawer test would be most sensitive at 90 degrees with nochange in varus or external rotation.Gollehou et al 38 studied the contribution of the LCL, posterolateralcomplex, and PCL in cadaver ligament cutting studies. They confirmedthat the LCL is the primary restraint to varus rotation in all degrees ofknee flexion with maximum displacement at 30 degrees. However,increases in varus rotation were small. Additional sectioning of the deepligament complex produced an increase in varus rotation (maximum at30 degrees) as well as an increase in the external rotation (maximum at30 degrees). If the LCL, posterolateral complex and PCL are sectioned,further increases in both varus rotation and external rotation areobserved at 60–90 degrees. Thus, isolated injuries to the posterolateralstructures will be most evident at 30 degrees. When seen in combinationwith PCL injuries, displacement will be the maximum 60–90 degrees.In a refinement of earlier studies when the popliteus was sectionedproximally Veltri et al 39 identified the popliteal attachment to the tibiaand the popliteofibular ligaments as individually important structurescontributing to the posterolateral stability of the knee. Sectioning ofthe LCL, cruciate ligament, popliteofibular, and popliteal attachmentto the tibia results in an increase in posterior translation, externalrotation, and varus rotation best demonstrated at 30 degrees of flexion.These findings not only further our understanding of the function ofthe ligaments and capsular structures but have implications forplanning reconstructive procedures.SummaryThe physical examination of the knee must be considered in thecontext of the patient’s age, history and, if possible, the mechanismof injury. Studies examining the accuracy of clinical examination afterinjury have found that the correct diagnosis is made pre-operativelyfrom 56% to 83% of the time. 40,41 Studies evaluating the cost benefitratio of MRI do not support its routine use.The diagnosis of extensor mechanism disorders is based largely onhistory and a composite picture of multiple soft physical findings.384