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Examination for Posterolateral Rotary Instability of the Knee

- Clinical Findings:
    - history: patient may complain of a subjective knee hyperextension sensation, and twisting or pivoting are also difficult;
    - lack of contained effusion is suggestive of posterolateral capsular injury;
    - look for diffuse tenderness over the posterolateral joint region, fibular head, and joint line;
    - gait:
          - patient may show an apparent increased tibia vara (due to external rotation-recurvatum deformity) both while standing as well as a
                  hyperextension thrust during the stance phase of gait;
          - note that lateral structures subjected to more force throughout normal gait cycle;
                 - mechanical axis of lower extremity: slightly medial to center of knee during stance phase;
                 - as a consequence, there is compression on the medial side of the joint and there is tension on the lateral side;
    - ACL exam:
         - note that in the report on posterolateral injuries, by Latimer et al (1998), as many patients had ACL tears as had PCL tears;
         - combined ACL and posterolateral corner injury will increase anterior and posterior translation, varus, external rotation, as well as internal rotation;
         - reference: Reconstruction of the Lateral Collateral Ligament of the Knee With Patellar Tendon Allograft. Report of a New Technique in Combined Ligament Injuries
    - PCL exam:
         - isolated PCL tear will not increase varus rotation or primary external rotation;
         - role in posterior stabilization increases throughout arc of flexion (significant stabilizing role at all angles
                 greater than 30 degrees and maximum stabilization at 90 deg);
         - in 90 deg of flexion, PCL is tight and is able to exert a secondary restraint against a varus moment and/or
                 external rotation as well as exerting a primary restraint against posterior translation;
    - LCL exam:
         - isolated LCL tear causes a mild varus angulation (maximal at 30 deg flexion);
         - complete posterolateral injury (w/ intact PCL results) will maximally increase varus, external rotation, and
                  posterior translation at 30° of flexion;
         - instability can be graded as mild, moderate, or severe with or without a firm end point;
    - reverse pivot shift test:
         - posterolateral corner of tibia drops off back of femur;
         - lateral opening of joint is detected when external rotation recurvatum test or reverse pivot shift tests are performed;
         - severity of reverse pivot shift correlates w/ severity of the instability (biceps avulsion, LCL, and capsular disruption);
    - external rotation test: (note that popliteus primary stabilizer to external rotation);
         - detects abnormal external rotation of tibia on femur associated w/ or in combination w/ excessive recurvatum;
         - test w/ patient prone or supine and compare it with the normal knee (simultaneously);
         - move the knee from about 10 deg of flexion to maximum extension while observing and palpating external rotation of proximal end of 
                  tibia as well as the amount of recurvatum;
         - compared to the normal knee, more than 10 deg of external rotation indicates significant injury;
         - posterolateral disruption w/ intact PCL:
                  - w/ knee in 30 deg flexion, will show excessive external rotation, posterior translation, and varus deformity;
                  - in 90 deg flexion, expect no abnormal external rotation compared to opposite side;                  
         - posterolateral disruption with torn PCL:
                  - markedly positive test indicates that PCL, posterolateral corner, and fibular collateral ligament are torn;
                  - when external rotation is maximal at 90 deg of flexion, it is likely that there is a concomitant PCL tear;
                  - look for increased posterior translation, varus rotation, and external rotation at all angles of knee flexion;
         - exam specifics:
                  - prone/supine (dial test)
                        - 30/90 degrees knee flexion
                        - ER torque
                        - 10 degree difference compared to contralateral leg  positive test
                  - ER recurvatum test
                        - supine
                        - grasp great toes of both feet & lifts
                        - both lower extremities off exam table
                        - positive test includes:
                              - relative HE (recuvatum)
                              - ER of tibia
                              - tibia vara medially
    - knee hyperextension:
    - posterolateral drawer test:
           - hip flexed 45 deg knee flexed 80-90 deg w/ tibia in 15 deg of external rotation;  
           - foot fixed
           - posterior tibial translation & tibial external rotation;
           - compare to contralateral side
    - peroneal nerve function:
         - 15% of posterolateral corner injuries have associated peroneal n. injury
         - one of the problems encountered in peroneal nerve repair following knee dislocations; (or other injuries) is that the location of the 
                  nerve injury may be well above the knee joint;
                  - in the case of knee dislocation, there may be concomitant tibial nerve division palsy;
    - references:
         - The posterolateral drawer test and external rotational recurvatum test for posterolateral rotatory instability of the knee.
         - Tests for posterolateral instability of the knee in normal subjects. Results of examination under anesthesia.

Classification of knee ligament instabilities. Part II. The lateral compartment.

Acute posterolateral rotatory instability of the knee.

Chronic posterolateral rotatory instability of the knee.

Posterolateral instability of the knee.

Posterolateral instability of the knee.

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures.

The role of the posterolateral and cruciate ligaments in the stability of the knee. A biomechanical study.

The role of the posterolateral and cruciate ligaments in the stability of the human knee: A biomechanical study.

Surgical Reconstruction of Severe Chronic Posterolateral Complex Injuries of the Knee Using Allograft Tissues.

Operative treatment of posterolateral instability of the knee.

The popliteofibular ligament: rediscovery of a key element in posterolateral instability.

The structure of the posterolateral aspect of the knee.

Treatment of acute and chronic combined ACL and Posterolateral Knee Injuries.

The posterolateral aspect of the knee: anatomy and surgical approach.

Reconstruction of the Lateral Collateral Ligament of the Knee With Patellar Tendon Allograft.  Report of a New Technique in Combined Ligament Injuries.

The Influence of the Integrity of Posterolateral Structures on Tibiofemoral Orientation When an Anterior Cruciate Ligament Graft is Tensioned.

The role of the popliteofibular ligament and the tendon of popliteus in providing stability in the human knee.

The Posterolateral Attachments of the Knee. A Qualitative and Quantitative Morphologic Analysis of the Fibular Collateral Ligament, Popliteus Tendon, Popliteofibular Ligament, and Lateral Gastrocnemius Tendon.