Every month there are new papers on ACL surgery and rehab appearing in the literature.  I do my best to stay up on them as this is one area of my practice I am extremely passionate about.  I am driven to understand as much as I can about both prevention and rehab, but find myself increasingly focused on preventing secondary ACL tears in my patients.

I feel poor movement patterns, muscle imbalances and inefficient neuromuscular control are major risk factors for athletes suffering a primary ACL tear.  We also know being female markedly increases injury risk.  Research also tells us that males are more likely to suffer a re-tear of the same side, whereas females are more likely to suffer a contralateral injury.

A study just published in the July issue of the American Journal of Sports Medicine looked at the incidence of second ACL injuries 2 years after a primary ACL reconstruction and return to sport.  In a nutshell, the findings were:

  • 24 months after ACLR and return to sport, patients are at greater risk (6x) to suffer a subsequent ACL tear compared to young athletes w/o a history of ACL injury
  • Female athletes in the ACLR group are 5x more likely to suffer a second injury
  • The contralateral limb of female athletes is at greatest risk

Click here to read the full abstract

This information is not surprising as I have seen it firsthand in 17 years as a physical therapist.  What we do not have much information about is how do the younger patients (e.g 15 and under) really recover from this injury.  When should they be cleared?  I worked with a young female soccer athlete who tore her ACL and medial meniscus at age 13.  She worked diligently with me in rehab 3x/week for about 6 months and then continued training with me at least 2x/week until she was about 1 year out from surgery.

She was medically cleared at 6 months to return to full activity, but her MD advised her to allow me to determine when she was really ready for return to sport.  She had a hamstring autograft reconstruction and arthroscopic medial meniscus repair in early April 2012.  There were no complications along the way, but I was still concerned about some movement inequality on her squat pattern as well as decreased landing control on the uninvolved side as well.  I had her further evaluated around 7 months post-op at UNC-Chapel Hill in their laboratory as part of an ongoing research study.

The report revealed significant weakness in the quadriceps and gluteus medius based on dynamometer and force plate data. Additionally, she had limited ankle mobility bilaterally and asymmetrical weight shift toward the uninvolved side with double leg landing on the force plate.  There was bilateral valgus on descent with jump landings.  Interestingly enough, hop testing done at 6 months post-op had revealed less than a 10% deficit across the board.  Her single leg squat was within 3 degrees of the uninvolved side as well.

Despite these favorable clinic numbers, I felt sending her back to soccer too soon was not in her best interests given the UNC data and my overall assessment of her movement patterns in cutting and landing tasks.  I opted to continue training and we slowly began a controlled return to practice plan at 10 months post-op with gradual return to full play at about 1 year out from surgery.  Keep in mind, many athletes are going back to sport in 6-8 months in many cases.  Fortunately, her parents were patient and bought in to this plan.

I am happy to say this particular athlete safely returned to sport and full play.  She stopped by to visit me this past week now over 2 years out from her injury.  She is playing at a high club level without limits.  I strongly believe our slow deliberate approach to rehab and her compliance/hard work made a huge difference in helping maximize her motor patterns and strength.

But with all that said, we still need more answers about how these younger and often skeletally immature athletes respond so we can best manage their care and long term health.  A new paper publish in the latest edition of Sports Health looked at a retrospective case series on patients who underwent all-epiphyseal ACLR from January 2008 – August 2010.  Isokinetic peak quadriceps/hamstring torque values and functional performance measures in unilateral hopping tasks were assessed and compared to the uninvolved side.  A limb symmetry index (LSI) of greater than or equal to 90% was considered acceptable.


16 patients between the age of 7 and 15 were treated by a single board certified pediatric sports medicine orthopaedic surgeon specially trained in this procedure.  Isok testing was done seated at 180 deg/sec.  Hop testing included single leg hop for distance, triple hop for distance, unilateral vertical jump and a unilateral timed lateral hop.


  • Complete data was collected on 16 of 47 eligible patients
  • All subjects included had maturity levels at Tanner Stage 2 or under
  • An Autologous hamstring graft was used for all subjects
  • Isok strength was assessed at a mean of 7.1 months (range of 3.02-12.56) and at that time 9 of 16 were able to achieve a satisfactory LSI for quadriceps strength, while 15 of 16 were able to attain a satisfactory LSI for hamstrings over the saem time interval
  • At a mean of 12.8 months (range of 5.39-24.39) only 6 of 16 patients were able to achieve greater than or equal to 90% on the functional hop tests
  • Overall, only 25% of patients were able to achieve a LSI of greater than or equal to 90% on all the tests (strength and hop) at an average of 15,42 months (range of 8.58-24.39)

Key takeaways

  1. There are marked lingering strength and functional performance deficits lasting more than a year after surgery
  2. Despite having a hamstring autograft, restoring quadriceps symmetry was a greater obstacle in this group
  3. Early gains in strength following ACLR are due to better activation of motor units, whereas later gains are more related to hypertrophy.  This later change may be more limited in younger patients due to maturity and the lack of circulating androgens.  This may account for delayed recovery of quad strength
  4. Pre-pubescnet athletes may struggle more with anxiety pre and post-operatively limiting their ability to work through discomfort after surgery as well as learning to work through the long rehab period
  5. The surgeon in this study utilized a period of limited weightbearing in the first 4-6 weeks post-op due to the skeletally immature population – this may also limit early quadriceps activation and slow the rehab process

Interestingly enough, my patient also had limited weightbearing for the first 4 weeks in light of the meniscal repair.  However, she did not have any trouble meeting the functional hop testing parameters at 6 months post-op.  She is closer to the top end of this age group, but it may also highlight differences in the rehab plan. That was one big limitation in this paper given the rehab was not done by the same PT so it is unclear how much of the given protocol was adhered to.  Another limitation was the lack of standardized assessment of strength and functional testing among patients.  I believe standard testing time frames help standardize treatment planning and improve consistency in follow-up.

Moving forward, we need to gather more information on this younger subset of patients so we know how best to handle their rehab process, in addition to safely returning them back to sport when they are truly ready for such high level activity.

Click here to read the Sports Health abstract