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Internal Rotation

- See:
  - Anteromedial Instability
  - Anterolateral Instability
  - external rotation

- Discussion:
- internal-rotation laxity increases w/ knee flexion, w/ largest amount (25 degrees) seen in the 20 to 40-degree range of knee flexion;
- of all of structures around the knee, only MCL and ACL play an important role in the restraint of Internal Rotation;
   - isolated cutting of either of these ligaments results in a marked increase in internal-rotation laxity, w/ MCL playing a larger role;
   - combined sectioning of ACL & MCL results in much more laxity than does sectioning of either ligament alone;
- loss of Anterior Cruciate Ligament in combination w/ loss of LCL or posterolateral structures, or both, also results in increased rotatory 
    laxity of approximately 35 degrees;
- cutting of PCL results in no increase in internal-rotation laxity;
- coupled anterior and medial translation occurs with internal rotation;
- loss of ACL results in increase in coupled anterior translation;
- isolated loss of PCL, LCL, or posterolateral structures does not affect the coupled motion;
- internal-rotation laxity is also increased following medial or lateral meniscectomy