But for proper knee function, the ACL is very important. If you are an active person, who wants to stay active and you feel instable within your knee, you need to fix a torn ACL (different methods and indications) regardless age.
By latest consensus in the AGA (German - Swiss - Austrian Arthroscopy society) conference in Munich 7.-9., September 2017, ACL repair is recommended, if there are no contraindications (diseases which forbid surgery).
In general if you are young and actively participating in sports you should have it repaired if you are older and less active a good rehab program should be sufficient.
Whether it's repaired or not rehab is the key. If you talk to professional strength coaches who have the longest follow up treating in dealing with patients with ACL repairs they say that the best result are with cadaver bone tendon and bone ACL. They cautioned against using the hamstring for repair even though many surgeons favor this technique. I guess the surgeons are listening to the people who follow the patients the longest
There are many variables when it comes to deciding if a patient should undergo ACL reconstruction. These include age, activity status, concurrent cartilage tears, and feelings of instability with activities of daily living, work, and leisure activities.
In general, I recommend ACL reconstruction for teens(sometimes younger) through age 40. After 40, if the patient is very active in pivot sports or has instability I would recommend repair. The ACL is a protective ligament for the meniscus cartilage and provides stability to the knee. As our life expectancy continues to climb, I expect ACL reconstruction to be recommended, routinely, for those over 40.
So, if you don't intend to use the knee very much, the ACL will not be used very much and the cartilage will not degrade as quickly. Those that want to participate in athletics will definitely need an ACL. In those patients that already have severe degeneration in the knee cartilage (arthritis), the ACL does not need to be repaired because the patient actually needs a knee replacement.
First is the person's activity level. The vast majority of people who want to participate or compete in cutting sports (soccer, basketball, football, baseball, tennis, etc.) need intact ACLs for knee stability and proprioception in making change of direction maneuvers. A very small proportion of the population has the neuromuscular development and coordination to make such maneuvers without the knee and limb control provided by an intact ACL.
Second is the instability in the knee. Some people who have no interest in participating in sports experience such a degree of instability in normal daily activities that they require ACL surgery to function. One of my professors experienced such a level of instability simply walking around his clinic that he underwent ACL surgery in his 40s just to be able to get through his work day.
The condition of the posterior horn of the medial meniscus is also a consideration. If the meniscus is intact, it acts as a secondary stabilizer against knee instability to the ACL and can act to provide stability when the ACL is absent. If a person has neither an ACL nor a medial meniscus, then the knee is usually very unstable and requires surgery.
Finally, one must consider the long term effects of ACL deficiency in the knee. Repeated episodes of pivot shifting or instability will damage the joint surface cartilage, leading to arthritis in the long term. ACL deficiency will put additional stress on the medial meniscus, leading potentially to meniscus tears and then cartilage damage and arthritis.
Thank you for your interesting question.
Kenneth R. Brooks, M.D.
If you have a torn ACL + meniscus tear, then you should have surgery to address both. If you have an isolated ACL tear and don't participate in activities noted above, then you could try to get by without surgery, but if you experience instability, then should have surgery.
Also, about 30% of ACL tears are eligible for primary ACL repair, where your own ACL is repaired, instead of a traditional reconstruction in which your ACL is replaced with a graft. A handful of surgeons in the U.S. currently perform primary ACL repair.
Vic Goradia, MD
Knee, Shoulder and Sports Medicine Specialist