Can A Ruptured ACL Heal?

Can A Ruptured ACL Heal?

A New Age Of ACL Management

Whether the anterior cruciate ligament (ACL) in the knee can heal or not is a simple question with a simple binary answer. However it is the cause of much mis-information and more recently some debate.  There is a growing body of evidence to give a clear and confident answer to this question, and that answer is ‘Yes the ACL can and does heal’. Sometimes the healing fails, some types of tears heal better than others, and the type of management post-injury affects healing rates; but the ligament can and often does heal.  This is contrary to traditional beliefs and many health professionals use the inability for it to heal as justification for surgery.

Blood Supply

The ACL is what is known as a intracapsular ligament;  originating and inserting completely  inside the ‘bubble’ of a joint capsule, and traditional thinking has been that as it is inside the capsule, it does not have blood supply, and therefore is unable to heal. However the ACL has actually been shown to have good blood supply and this was proven in   this comprehensive study from the 1990’s by Italian researchers who identified the exact arteries that supply the ACL. In Japan, doctors often aspirate knee joint capsules to assist with their diagnosis,  if fluid withdrawn from inside the knee joint capsule has blood in it, the thinking is that the injury is likely to be an ACL. This blood comes from inside the joint capsule indicating there is blood supply inside the capsule.

Partial ACL Tears

It was also thought that the ACL does not partially tear, it was either fully ruptured or in-tact. Although there is a school of thought that partially torn ACLs are not functional and therefore not useful, MRIs have shown many ACL injuries to have a partially intact ligament. Partially torn ACLs are easier to repair rather than the typical replacement of a reconstruction. Repairs are when the surgeon stitches the tear back together and this 2020 study by Fereti showed ACL repair to avoid the extra morbidity and harvest-related complications, leading to a faster recovery from the operation. While ACL repairs are currently rarely performed, we’d expect an increase in the popularity of this surgery.

Research On ACL Healing

The best study currently published on ACL healing is a 2017 Japanese randomised control trial by Ihara and Kuwano.. In their study, they followed up on 102 patients with recent ACL tears  and at 6 months post injury over 80% showed a fully healed ACL. The authors used a specific healing protocol that they did not fully revel, but they had the participants in braces within 3 weeks of injury. There is another study being conducted in Sydney which is showing even higher healing rates, however this is not yet published. In our clinics in the ski fields of Japan, we see patients with newly torn ACLs every day and have seen many full ACL ruptures progress to having a fully healed and in-tact cruciate ligament, confirmed with MRI.

How should we manage an ACL Rupture?

So we can say with some degree of confidence that the ACL can and does heal, what do we do with this information? Firstly the key message for patients is critical – Do not to rush into surgery. Most people who rupture an ACL follow the path of the current medical model. Twist the knee, hear a pop > See a GP > GP unsure of injury type   > refer for MRI and to knee surgeon > MRI shows ACL rupture > see knee surgeon who diagnoses ACL rupture > Reconstruction surgery scheduled.  There is often little discussion of conservative management or healing.

To understand the ideal environment for the ACL to heal, more randomised control trials are needed to test varying different management protocols to stimulate healing. The variables we need to understand include whether to use of a brace or not, the type of brace to use, the optimal position to set the brace at various durations post injury and the optimal weight bearing and activity levels. It may be some years before a universally accepted protocol is settled upon, if ever.

What Should I Do If I Rupture My ACL?

Aside from those who have short term sporting goals, people who have a recent ACL rupture, should delay surgery at least 3 months. As soon as they can post injury they should commence work with a physiotherapist to first calm and then strengthen the knee. As the optimal protocol for healing is unclear, it seems a good idea to get into a supportive brace, avoid bending the knee beyond 90 degrees (to prevent the stumps of the ACL moving apart) and avoid high intensity sports, especially those involving twisting. The patient must be reassured many times to ‘trust the knee’ so psychological affects of the ACL are minimised. If at the end of the 3 months rehabilitation the ACL does not heal the patient may find function is good enough to refrain from surgical management. However even if he knee is still unstable and surgery is the chosen option, the knee will be calm, strong, and stable going into the operation and be in great shape for an excellent post-operative rehabilitation. Those three months of strengthening will not have been wasted.


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