Analyzing ACL Reconstruction Outcomes: Why Measuring Knee Extension Is Critical

It is estimated that there are approximately 200,000 injuries to the anterior cruciate ligament (ACL) per year in the US alone with the higher risk sports being soccer, football, and skiing. Individuals who participate in these sports are 10 times more likely to rupture the ACL when compared to other sport activities. There is a desire of many athletes to have surgery as soon as possible to be able to return to their sport quickly, and because of this request, there seems to be a trend in some areas of the country to appease the patient for fear of losing them to another surgeon. However, the research is clear that those who have surgery before the knee has full extension and minimal to no swelling, have a higher risk of complications postoperatively and poor long-term outcomes.

The staff at Shelbourne Knee Center looked at long term outcomes based on normal or abnormal extension, with or without the presence of structural abnormalities, following ACL reconstruction. Structural abnormalities at the time of an ACL injury can include meniscus tear, chondral injury, or a combination of the two. There were 3382 patients following an ACL reconstruction between 1982 and 2011 using a patellar tendon graft. Those who had previous osteoarthritis, revision (previous ACL surgery), and bilateral ACL reconstruction were excluded from the study. There were 903 patients with subjective, objective, and radiographic data at a mean 17.7 years from surgery. They were divided into four groups based on their structural abnormality: normal (group 1), meniscus tear (group 2), chondral injury (group 3), or both (group 4). They were followed up at a minimum 10 years postoperative to re-assess range of motion, complete an International Knee Documentation Committee survey (IKDC), and obtain radiographs. Based on the IKDC, abnormal knee extension is defined as being more than 2 degrees off compared to the opposite knee. They also compared the extension range of motion at 2 months postoperative to this long-term postoperative motion.

Study Findings

The results of this study showed that patients with abnormal knee extension at 2 months postoperative were 6.4 times more likely to have abnormal knee extension at long term follow up (p<.001). At long term follow up, 84% of these patients had normal knee extension. The rate of moderate to severe knee osteoarthritis for groups 1-4 was 5%, 12%, 16%, and 25%, respectively (p<.05). For each group, the patients with normal extension had statistically significantly lower rates of osteoarthritis compared to those with abnormal extension: group 1 = 3% vs 27%; group 2 = 9% vs 29%; group 3 = 12% vs 60%; and group 4 = 18% vs 46%. For those patients who had normal extension, they had statistically significantly higher IKDC scores compared to those with abnormal extension. Overall, patients who had abnormal knee extension were 5 times more likely to have osteoarthritis compared to those with normal extension. Also, this study showed that patients with a meniscus tear were 2.4 times more likely to have osteoarthritis and those with chondral injuries were 2.7 times more likely when compared to those without a structural abnormality, indicating that a loss of knee extension long term results in more negative outcomes than meniscus tears or chondral injuries.

The clinical relevance of this study should help direct clinicians into educating the patients about best timing of surgery and ensuring that patients have their full knee extension, equal to the opposite side, to avoid negative long-term outcomes.

This study was submitted and accepted for the APTA Combined Section Meeting in San Diego, CA as a podium presentation and poster presentations at the meetings for AOSSM in Washington DC and AAOS in Las Vegas, NV.