The effect of insufficient quadriceps strength on gait after anterior cruciate ligament reconstruction. Clin Biomech (Bristol, Avon). 2002 Jan;17(1):56-63. Lewek M1, Rudolph K, Axe M, Snyder-Mackler L.
From the study:
Individuals following anterior cruciate ligament rupture often demonstrate reduced knee angles and moments during the early stance phase of gait. Alterations in gait can neither be ascribed to instability nor to quadriceps weakness alone when both are present.
Twenty-eight individuals with complete anterior cruciate ligament rupture (10 patients with acute rupture, 8 patients following reconstruction with quadriceps strength >90% of the uninvolved side [strong-anterior cruciate ligament reconstructed group], and 10 patients after reconstruction with quadriceps strength <80% of the uninvolved side [weak-anterior cruciate ligament reconstructed group]), and 10 uninjured subjects underwent an examination of their lower extremity to collect kinematics, kinetics, and electromyography during walking and jogging. Anterior cruciate ligament reconstruction was arthroscopically assisted and a double loop semitendinosis-gracilis autograft or allograft was used as a graft source. All reconstructed subjects had stable knees, full range of motion, and no effusion or pain at the time of testing (more than three months after surgery).
Knee angles and moments of the strong group were indistinguishable from the uninjured group during early stance of both walking and jogging. The weak subjects had reduced knee angles and moments during walking, and jogged similarly to the deficient subjects. Regression analysis revealed a significant effect between early stance phase knee angles and moments and quadriceps strength during both walking and jogging.
Inadequate quadriceps strength contributes to altered gait patterns following anterior cruciate ligament reconstruction.
Muscle inhibition was ruled out as a factor because percent of muscle recruitment was similar between groups. Pain was ruled out as a factor because all subjects were painless. Weaker subjects were a few weeks further out post-op (20.8 weeks vs 14.3 for the stronger group), so recovery time was not a factor. Weak subjects were considered anyone with the repaired side quadriceps <80% of their non-repaired side (averaging 67.6%) while strong subjects was anyone with quadriceps >90% of their non-surgical side (average 95.3%) which gives us good information with regards to what strength levels are necessary to normalize gait (how you walk). The entire paper was a fascinating read with much pertinent background information given in the introduction and discussion. The researchers found the abnormal gait of weaker ACL reconstruction patients to be very similar to ACL deficient patients (not repaired) and suspect this would likely lead to similar early joint degeneration/arthritis, and thus negate much of the the point of the reconstruction in the first place.
The take home message for physical therapists and patients alike after ACL reconstruction is that you really want to restore a normal walking pattern. To do so the best strategy is to restore quadriceps strength to >90% of the contralateral side, but this must be done safely, respecting the healing process of the graft so as to not damage the repair. It probably isn’t a bad idea to get hamstrings, calves, hip abductors and adductors >90% while you are at it. After surgery, strength is best increased with progressive resistance exercise, and when active muscle contractions are inhibited, electric muscle stimulation. As is usually the case, time in physical therapy is limited, so time spent on passive modalities de jour (soft tissue mobilizations, arthrokinematic joint mobilizations, ASTYM, Graston Technique, dry needling, magnets, psychic surgery, whatever) is likely time wasted.
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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.