Anterior Cruciate Ligament Injury Follow-up

Updated: Jun 16, 2016
  • Author: Matthew Gammons, MD; Chief Editor: Sherwin SW Ho, MD  more...
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Once quadriceps strength reaches 65% of the opposite leg, sports-specific activities may be performed; this usually occurs within 5-8 weeks postsurgery. This may be tested using a Cybex machine. The athlete may return to activity when the quadriceps strength has reached 80%, which is usually after at least 3-4 months of sports-specific therapy.

According to a study by Grindem et al, returning to level I sports after ACL reconstruction leads to a more than 4-fold increase in reinjury rates over 2 years. The study also found that return to sport 9 months or later after surgery and more symmetrical quadriceps strength prior to return substantially reduce the reinjury rate. [25]

A study by Kyritsis et al found that athletes who did not meet the discharge criteria before returning to professional sport had a four times greater risk of sustaining an ACL graft rupture compared with those who met all six return to sport criteria. The study also found that hamstring to quadriceps strength ratio deficits were associated with an increased risk of an ACL graft rupture. [26]



The current failure rate for ACL reconstruction is approximately 8%. The 3 major categories of failure in an ACL reconstruction are (1) arthrofibrosis (due to inflammation of the synovium and fat pad), (2) pain that limits motion, and (3) recurrent instability, secondary to significant laxity in the reconstructed ligament. These factors may be related to the surgical procedure (eg, malpositioned tibial or femoral tunnels, misplaced hardware, inadequate notchplasty).

  • Anterior placement of a tibial tunnel may result in graft impingement. If a tunnel is placed too posteriorly on the femoral side, the posterior cortex of the femur may be violated.

  • A graft also may fail due to a lack of incorporation, secondary to rejection or stress shielding.

  • Trauma from re-injury or aggressive rehabilitation also may cause graft failure. The incidence of graft re-rupture is approximately 2.5%.

Other complications include patella fractures and patella-tendon ruptures. Reflex sympathetic dystrophy, postoperative infection, and neurovascular complications are rare (each accounting for less than 1% of complications). The rate of postoperative deep venous thrombosis is approximately 0.12%.



Patients treated with surgical reconstruction of the ACL have long-term success rates of 82-95%. Recurrent instability and graft failure is seen in approximately 8% of patients.

A study by Brody et al found increased rates of chondral damage in patients who underwent partial meniscectomy compared to patients with a previous meniscal repair or no history of meniscal injury. [27]

Knee scores of those treated nonoperatively have fair/poor results up to 50% of the time. As many as 40% of patients treated nonoperatively have no episodes of giving way. The knee scores in this group may be too sensitive, not accurately representing the clinical situation.

Patients with ACL ruptures, even after successful reconstruction, are at risk for osteoarthrosis. The goal of surgery is to stabilize the knee, decrease the chance of future meniscal injury, and delay the arthritic process.

In a retrospective study of 135 young athletes (average age, 14 years) who underwent ACL reconstruction, Anderson et al found that the timing of surgery was related to the risk of secondary knee injuries. Compared with patients who had surgery within 6 weeks after an ACL injury, those who underwent surgery 6-12 weeks after injury had a 1.45 times higher risk of lateral meniscus injury, and those who underwent surgery more than 12 weeks after injury had a 2.82-fold increased risk. Risk for medial meniscal tears was 4.3 times higher when surgery was delayed at least 6 weeks. Other risk factors for secondary knee injuries were younger age, resumption of participation in sports before surgery, and earlier episodes of knee instability. [28]