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- Mechanism: ACL Tear:

- Physical Exam of ACL Tears:  (see knee exam)
     - Anterior Drawer Test
     - Anteromedial Rotatory Stability:
     - Anterolateral Rotatory Instability
     - Clunk Test
     - Lachman
     - Losee Test
     - Partial ACL
     - Pivot shift
     - Reverse Pivot Shift Test
     - Hemarthrosis:
           - greater than70% of pts w/ acute hemarthrosis  will have ACL tear;
           - severe swelling of the knee typically develops within two hours of injury because of hemarthrosis;
           - hemarthrosis will develop over 6-24 hours;
           - if effusion develops immediately after injury, one should suspect an osteochondral fracture;
                  - presence or absence of fat in aspirated fluid is key distinction;

- Discussion:
      - ensure that patient has a FROM and no indication of arthrofibrosis:
      - pivot shift with a positive Lachman's;
      - combined injuries:
              - posterior laxity;
              - MCL instability:
                       - in most cases, the torn MCL will go on to heal if treated conservatively;
                       - ACL reconstruction should be delayed until medial laxity is not present, otherwise the combined instability may comprimise the final result;
              - posterolateral instability:
                       - should be managed operatively along with the ACL reconstruction;
                       - neglected posterolateral instability may lead to ACL reconstruction failures; 
                       - ref: Does Physiologic Posterolateral Laxity Influence Clinical Outcomes of Anterior Cruciate Ligament Reconstruction?
              - meniscal tear:
                       - strongly consider repair at the time of ACL reconstruction;
                       - pass sutures prior to the ACL reconstruction but delay tying sutures down until the reconstruction is completed;        
      - references:
              - Treatment of acute isolated and combined ruptures of the anterior cruciate ligament. A long term follow up study.  
              - Decreased range of motion following acute versus chronic anterior cruciate ligament reconstruction.

- Diff Dx:
    - consider quadriceps or patella tendon rupture;
    - PCL ruptures may give a "false positive" Lachman test;

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- Radiographs:
    - hyper-extension lateral view allows assessment of slope of intercondylar roof in relation to the tibial plateau;
           - this may help with placement of the tibial tunnel (helps avoid graft impingement);
    - Segond fracture
           - small avulsion frx of lateral tibial condyle just below joint line is now recognized as a sign of injury of ACL;
           - small avulsion frx of proximal part of the tibia that is seen just proximal to fibular head on the anteroposterior roentgenogram, is
                   nearly always associated w/ torn ACL;
           - references:
                   - The Segond Fracture: A Bony Injury of the Anterolateral Ligament of the Knee
                   - The Segond fracture of the proximal tibia: A small avulsion that reflects major ligamentous damage.
    - references:
           - Patella baja in anterior cruciate ligament reconstruction of the knee.
           - Lateral capsular sign: x-ray clue to a significant knee instability.   
           - Relation of the fibular head sign to other signs of anterior cruciate ligament insufficiency. A follow-up letter to the editor.
           - Patellar tendon graft reconstruction for midsubstance ACL rupture in junior high school athletes. An algorithm for management.
           - Assessment of patellar height after autogenous patellar tendon anterior cruciate ligament reconstruction.
           - Fracture of the posterior aspect of the lateral tibial plateau: radiographic sign of anterior cruciate ligament tear. 
           - Does Posterior Tibial Slope Influence Knee Functionality in ACL-Deficient and ACL-Reconstructed Knee?
           - Anatomic Graft Placement in ACL Surgery: Plain Radiographs Are All We Need
           - Posterior Tibial Slope Influences Static Anterior Tibial Translation in Anterior Cruciate Ligament Reconstruction

A Minimum 2-Year Follow-up Study

             

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- MRI of Knee:
    - normal anatomy:
         - distal ligament may show a striated signal caused by interspersed fat and synovium between the 2 bundles;
         - proximal ligament appears dark
    - any discontinuity or signal change in the ligament is indicative of ACL tear;
    - indirect signs of ACL tear:
         - always look for signs of additional injury (meniscal tear, PCL tear, LCL tear);
         - femoral osteochondral lesions and/or tibial plateau bone bruises may diminish the eventual postoperative result; 
                 - look for increase in signal on T2-weighted images and decreased signal on T1-weighted images
         - often there will be focal areas of increased signal in the posterior aspect of lateral tibial plateau and mid portion of the lateral femoral condyle. 
                 - signal changes occurs as a consequence of pivot shift injury: 
                         - combination of signal changes in lateral femoral condyle and posteror lateral tibial plateau results from of a valgus-
                                    external rotation of the femur on the fixed tibia;
         - abnormal slope of ACL;
         - avulsion of the anterior tibial spine;
         - segond fracture: capsular avulsion fracture of the lateral tibial plateau;
         - kissing contusions involving the anterior tibia and femur resulting from hyperextension injury;
         - references:
               - The accuracy of selective magnetic resonance imaging compared with the findings of arthroscopy of the knee.
               - "Bone Bruises" on magnetic resonance imaging evaluation of anterior cruciate ligament injuries.  
               - Occult posttraumatic osteochondral lesions of the knee: prevalence, classification, and short-term sequelae evaluated with MR imaging

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- Associated Findings:
    - varus knee:
          - whereas a varus knee probably does not cause ACL tear, it is well known that a varus knee will have a negative influence on both operative and non-op treatment;
          - w/ signficant varus deformity consider high tibial osteotomy prior to ACL reconstruction;
          - references:
                 - High tibial osteotomy and ligament reconstruction in varus angulated, anterior cruciate ligament-deficient knees: a 2-7 year follow up study.  
    - osteochondral defects
    - meniscal tear:
          - menisci may become trapped between femoral and tibial condyles.
          - vertical longitudinal & " bucket-handle tear;"
          - as tibia subluxates anteriorly, the posterior horns of menisci become trapped between articular surfaces of femur and tibia;
                 - if torn meniscus fragment remains forward of the femoral condyle when the tibia reduces, knee is "locked;"
          - note that the combination of ACL tear and meniscal tear is especially likely to contribute to instability, and early osteo-arthritis;
                 - ACL tears combined w/ medial meniscal tears result in more anterior translation than lateral meniscal tears;
          - management:
                 - Shelbourne KD and Johnson GE (1993), advocate staged treatment of concomitant bucket hand and ACL injuries;
                 - theoretical advantages of staged repair and reconstruction:
                        - more aggressive use of repair rather than removal of a displaced torn meniscus;
                        - prevention of problems in regaining range of motion;
                        - allows a second look to judge the success of meniscal repair;
                        - allows time for the patient to prepare for ACL reconstruction;
          - references:
                 - Locked bucket-handle meniscal tears in knees with chronic anterior cruciate ligament deficiency.                                          
    - MCL tear:
          - treated non operatively, most MCL tears will heal with non operative treatment;
          - some surgeons will delay ACL reconstruction until there is near complete resolution of medial instability;
          - references:
                 - The treatment of acute combined ruptures of the anterior cruciate and medial ligaments of the knee.
                 - Reconstruction of ACL alone in the treatment of a combined instability with complete rupture of MCL. A prospective study.
    - posterolateral instability:
          - these patients may demonstrate an asymmetric recurvatum deformity, which is most pronounced during gait;
          - exam: external rotation recurvatum test and reverse pivot shift test
          - LCL instability should be managed concurrently w/ ACL reconstruction;
          - it is important to distinguish this type of instability from one plane posterior instability;
          - isolated PCL/ACL reconstruction will correct the one plane instability but will not correct the rotatory instability;
                 - in fact, ACL reconstruction may actually increase the patient's sensation of rotatory instability;
          - reference:
                 - Treatment or acute and chronic combined anterior cruciate ligament and posterolateral knee ligament injuries.   
    - incomplete knee extension:
          - most often is a result of a "cyclops lesion," which is due to a stum