Natural History of the ACL-Deficient Knee

- See: Partial ACL Deficiency:

- Discussion:
    - left untreated, the torn ACL leads to anterior laxity, rotatory instabilities, and meniscal tears;
    - there is a definite increase in X-ray changes of DJD
    - 1/3 of pts w/ isolated ACL injuries will show minimal instability
    - 2/3 will show instability;
    - patients who intend to return to pre-injury athletic activity level will find that re-injury is common;
           - re-injury may occur in over 50% of young patients over one year;
           - re-injury may occur in over one third of middle aged patients after one year;
    - effects on the menisci: (see ACL and meniscal tears:
           - at the time of injury approximately 1/3 of patients will have meniscal tears, which are equally divided between
             the medial and lateral compartments;
           - the anterior instability produced by the ACL tear often leads to longitudinal meniscal tears in the medial compartment;
           - the degenerative arthritis seen in ACL deficient knees may be more related to concomitant meniscal tears than it is to
             the ACL deficiency;
    - effects on chondral surfaces:
           - cartilage damage will correlate with length of time from injury;
           - medial compartment will often show more damage than the lateral compartment;
    - quadriceps avoidance gait: (see: gait)
           - most patients will alter their gait in order to avoid anterior displacement of the tibia which occurs with quadriceps
             contraction;
           - between 0 to 45 deg of flexion, contraction of the quadriceps will cause anterior translation of the quadriceps
             (which is normally resisted by the ACL);
                  - maximum anterior translation of the tibia occurs at 15-25 deg of flexion;
    - late degenerative changes:
           - late degenerative changes are most often seen in ACL deficient knees with meniscal injury;
           - ref: Long term osteoarthritic changes in anterior cruciate ligament reconstructed knees.
             NM Jomha MD et al. CORR No 358 1999 p 188.

- Non Operative Treatment:
    - there is no good evidence that brace wear decreases the rate of re-injury;
    - older patients w/ isolated ligament injury who are willing to moderate their activity will
      find non-operative treatment to be satisfactory in the majority of cases (over 80%);