ACL Reconstruction, Leg Extensions Safe but Timing is Everything

Early versus late start of open kinetic chain quadriceps exercises after ACL reconstruction with patellar tendon or hamstring grafts: a prospective randomized outcome study. Knee Surg Sports Traumatol Arthrosc. 2007 Apr;15(4):402-14. Epub 2007 Jan 12. Heijne A, Werner S.

From the study:

The purpose of the present investigation was to evaluate physical outcome after anterior cruciate ligament (ACL) reconstruction with early versus late initiation of open kinetic chain (OKC) exercises for the quadriceps in patients operated on either patellar tendon or hamstring grafts. Sixty-eight patients, 36 males and 32 females, with either patellar tendon graft (34 patients) or hamstring graft (34 patients) were enrolled in this study. All patients were randomly allocated to either early (the 4th postoperative week) or late (the 12th postoperative week) start of OKC exercises for the quadriceps, resulting in four subgroups: patellar tendon reconstruction, early start (P4) or late start (P12) of OKC quadriceps exercises, hamstring tendon reconstruction, early start (H4) or late start (H12) of quadriceps OKC exercises. Prior to surgery and 3, 5 and 7 months later, assessments of range of motion (goniometer), anterior knee laxity (KT-1000), postural sway (KAT 2000), thigh muscle torques (Kin-Com dynamometer) and anterior knee pain (anterior knee pain score) were evaluated. No significant group differences were found in terms of range of motion 3, 5 and 7 months postoperatively. The H4 group showed a significantly higher mean difference of laxity over time of 1.0 mm (CI: 0.18-1.86) than the P4 group (P=0.04). Within the same type of surgery, the H4 against the H12, the mean difference over time was 1.2 mm (0.37-2.1) higher in the H4 group than in the H12 group (P=0.01). There were no significant group differences in terms of postural sway or anterior knee pain at the different test occasions. Significant differences in trends (changes over time) were found when comparing the four groups, for both quadriceps muscle torques (P<0.001) and hamstring muscle torques (P<0.001). All groups, except the P4 group, reached preoperative values of quadriceps muscle torques at the 7 months follow-up. In the H4 and the H12 groups, significantly lower hamstring muscle torques at the 7 months follow-up compared with preoperative values were found. In conclusion, early start of OKC quadriceps exercises after hamstring ACL reconstruction resulted in significantly increased anterior knee laxity in comparison with both late start and with early and late start after bone-patellar tendon-bone ACL reconstruction. Furthermore, the early introduction of OKC exercises for quadriceps did not influence quadriceps muscle torques neither in patients operated on patellar tendon nor hamstring tendon grafts. On the contrary, it appears as if the choice of graft affected the strength of the specific muscle more than the type of exercises performed. Our results could not determine the appropriate time for starting OKC quadriceps exercises for patients who have undergoneACL reconstruction with hamstring tendon graft. Future studies of long-term results of anterior knee laxity and functional outcome are needed.

Chad’s comments:

This is another great ACL/exercise study that did change how I treat my ACL patients. As noted in another blog, open kinetic chain exercises like resistive leg extensions do help isolate quadriceps and thus strengthen them. That strength does allow better return to sports when added to a program consisting of closed kinetic chain exercises like squats, lunges, etc.

What this study found was that patellar tendon graft ACL repairs benefit from leg extensions as early as 4 weeks post-op without overstretching the graft. Hamstring tendon graft ACL repairs had increased laxity when leg extensions were started at 4 weeks, but remained tight if the leg extensions were started 12 weeks out. The study also found that delaying the start of OKC exercises to 12 weeks did not significantly impair quadriceps strength when measured 7 months post-op. The 4 week groups started knee extensions with range of motion limited 90-40 degrees, not progressing to 0 degrees extension until 6 weeks post-op. The 12 week group started 90-0 degrees knee extensions immediately at 12 weeks. So, 12 weeks seems safe enough to start resistive leg extensions 90-0 degrees with hamstring graft ACL reconstructions.  Starting any earlier than that, you are risking a lax knee joint, reinjury and perhaps early arthritic changes. The 4 week start knee extensions are apparently safe with the patellar graft, with the caveat of early limited range of motion.

Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember SpineFit Yoga for you or someone you know in the future.

Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.


2 responses to “ACL Reconstruction, Leg Extensions Safe but Timing is Everything”

  1. Johann Y.


    Will the laxity of the knee decrease or be back to normal at a certain period of time even if leg extensions streatched the graft on the early stages of acl reconstriction? Thank you.

    1. Chad Reilly

      Hi Johann,

      Good question and unfortunately I don’t have a good answer. I’m not aware of any research looking at it one way or another. Thus if it were me I’d play it safe and avoid leg extension until safe, rather then plan on things tightening up later. If I had already overstretched the ligament I would probably avoid future ACL stretching activities (like leg extensions) and hope things shrink up. Unfortunately I don’t know of a good way to accurately measure if that happened or not.

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