When to Return to Sports after ACL surgery, A Timeline

When to Return to Sports after ACL surgery, a timeline

I recently read an interesting research report about the recovery timeline after surgery from a ruptured ACL (anterior cruciate ligament). The title grabbed my attention and after reading the article it seemed pretty remarkable, and I wanted to share it on our blog.  It actually really made me think of many people I have talked to in life that had tried to go back to sports to soon, and then ruptured their ligament again.  The journal article focused on the difference in those patients who delayed their return to sport after 9 months from the day of surgery to those who returned sooner than 9 months.  Since, approximately, 1 in 4 patients who are 25 years of age or younger return to high-risk sports, this seems like a very important piece of information to understand for student athletes and their parents. ¹

The article was in The Journal Orthopaedic and Sports Physical Therapy and was titled “Young Athletes Who return to Sport Before 9 months After ACL Reconstruction Have a Rate of New Injury 7 times That of Those Who Delay Return.”  Again, the title intrigued me and the research design was very interesting.  The authors included 159 athletes who were involved in knee-strenuous sports. The criteria for inclusion was the performance of 2 strength tests and 3 hop tests that were extracted from a rehabilitation registry when the athletes were finishing up their rehab.  Additionally, a questionnaire was answered by the athletes ages 15-30 years old who had participated in knee-strenuous sports prior to a primary ACL reconstruction surgery.  The study noted two very interesting ideas:  1.) that the higher the level of sport participation prior to the ACL injury, then the higher the rate of a second ACL injury, and 2.) that there was no association between post-rehab symmetrical muscle quadriceps strength and a second ACL injury. 

The final conclusions of the article were perhaps the most enlightening. The article noted that returning to sport prior to 9-months after the reconstruction surgery was associated with a 7-fold increased rate of sustaining a second ACL injury even when the quadriceps strength is symmetrical to the opposite side.   The idea being that the muscle tone and strength has returned to normal, and thus the knee should be ready to go back to sport; but obviously that is not the case. These conclusions when we think about it further are not that surprising. To understand why this is the case we have to understating what is going on at the cellular and histological level of healing. 

According to the chart above that was first published in 1992 by Kevin Wilk and Dr. James Andrews and since has shown similar data², the initial graft strength of a 10 mm graft right after the surgery is about 120% of that of an intact ACL.  A 14mm graft is even stronger.  However, at 6-8 weeks post-op the graft strength deteriorates to about 60% of the intact ACL.  This represents the bottom of the curve.  The graft then starts a revascularization process, which is what the graft has to do to start becoming “part of the host” and needs to start functioning as a ligament instead of a surgically cut piece of tendon.  This means that the blood vessels start innervating the new tissue to provide it with oxygen and nutrients that it will need to function as an organic and living tissue.  If this revascularization process does not occur then the tissue will degenerate and become useless. The process of revascularization takes some time.  The graft starts to morph into a ligament and at 12 weeks the graft strength is back up to 80% and then at 52 weeks (one-year) the graft is just below 100% of the intact ACL.

We have seen and heard people try to return to sport way to soon and end up with a second and even a third revision.  Perhaps the worst case I have heard was a colleague of mine trying to return to Division 1 women’s soccer at 3 months post ACL reconstruction (she didn’t know better at the time and I didn’t know her).  She sustained a re-tear one of first practices back. Therefore, it is important for athletes and parents to recognize that return to sport prior to 9 months is very risky and they should be advised to wait till the graft revascularizes fully.  Because no matter how strong the muscle structure might be around the repaired ACL, the shear forces and strain that the cutting, jumping, sprinting, stopping, twisting and falling can put on the ACL are not sustainable with an ACL that is not functioning near 100%.  That may seem pretty obvious on face value, but when your itching to get back out on the field, court, track, ice, or snow it is a hard decision to make, trust me, we know.  For those of you looking to get back to sport after ACL reconstruction – Have Fun but be prudent.  If you ever have any question regarding when to return to sport after your ACL reconstruction ask an experienced sports physical therapist or just a message us through our website or give us a call at 678-667-3435. 

1. Beishcer S., et al., Young Athletes Who return to Sport before 9 months After ACL Reconstruction Have a Rate of New Injury 7 times That of Those Who Delay Return. Journal Orthopaedic and Sports Physical, 2020. 50(2): p. 83-91.

1. Wilk K. and Andrews J., Current Concepts in the Treatment of Anterior Cruciate Ligament Disruption.  Journal Orthopaedic and Sports Physical, 1992. 15(6): p. 279-293.