Dr. Ron Losee from Ennis, Montana, was the first to describe a test for ACL instability. It was called the Losee maneuver for many years. Now it's sometimes referred to as the "pivot-shift" test.
When the test is done, the patient is asked, "Is this how your knee feels when it gives out?" The doctor doesn't always feel a change in the knee during the test, so the patient's report is important.
A positive pivot-shift may be a sign that surgery is needed to repair the torn ligament. There is a device that measures laxity between the two knees (a KT-2000). The results of one test usually aren't enough to tell which patients need an operation. Tests like the pivot-shift, along with several others, are still important.
If you are interested, Dr. Losee has written a book about his experiences. It's called Doc: Then and Now with a Montana Physician. To read more about this book, go to: http://www.smithsonianmag.si.edu/smithsonian/issues95/may95/book_may95.html#doc.