After anterior cruciate ligament (ACL) reconstruction, weak quadriceps are common. “There are many different theories about why patients can’t get their strength back after ACL reconstruction. I wanted to look at the effect of knee range of motion (ROM) on return to quadriceps strength,” says Sarah Eaton, PT, DPT, ATC, LAT, a physical therapist/athletic trainer at Shelbourne Knee Center.
Eaton studied 978 patients who underwent primary ACL reconstruction using a contralateral patellar tendon graft at Shelbourne Knee Center from 1988–2012. She was especially interested in knee extension, lack of which has been linked to quadriceps weakness.
Study Methods
All patients who participated in the study had completed Shelbourne Knee Center’s accelerated ACL post-op rehab protocol and post-op testing at one year. The accelerated ACL post-op rehab protocol focuses on improving ROM before strengthening.
Using the International Knee Documentation Committee (IKDC) scoring system, Eaton categorized patients into two groups based on their ROM measurements:
- Normal group: Knee extension within 2° and knee flexion within 5° of the non-involved knee
- Abnormal group: Lack of normal extension or flexion.
She evaluated quadriceps strength using Cybex isokinetic dynamometer testing at 180°/sec and 60°/sec.
Normal ROM Enables Quadriceps Strength
Of the 978 patients who participated in the study, 891 patients had normal ROM and 87 patients had abnormal ROM at one year post-op.
Patients with normal ROM in the ACL leg at one year post-op had stronger quadriceps and were more likely to have quadriceps strength within 10% of the non-involved leg than those with abnormal ROM (1). Many ACL rehabilitation programs require a difference of 10% or less between the two legs before return to sport. Specific findings are:
- Symmetrical strength within 10% between the knees:
- 60% of patients with normal ROM
- 47 % of patients with abnormal ROM
- Mean quadriceps strength at 60°/seconds:
- 106% in the normal ROM group
- 101% in the abnormal ROM group
- Mean quadriceps strength at 180°/seconds:
- 101% in the normal ROM group
- 97% in the abnormal ROM group.
Implications for Clinical Practice
“We’re almost overthinking what we need to look at and do from a rehab standpoint. If you get the patient’s ROM back, strengthening the quadriceps is much simpler,” says Eaton.
Physical therapists can easily change how patients do rehab after ACL reconstruction surgery to focus on restoring normal ROM as soon as possible. This, says Eaton, provides the best chance of regaining quadriceps strength.
Eaton shared results of her study at the American Physical Therapy Association Combined Sections Meeting in January 2019 and at Community Health Network’s 4th Annual Multidisciplinary Symposium at the University of Indianapolis in May 2019. “We don’t keep what we do secret. We want everyone to have education and be empowered to help their patients get the best knee care,” she says.
Along with conducting her own research, Eaton also participates in the Shelbourne Knee Center research program, which tracks patient outcomes and studies factors related to those outcomes. Data covering 38 years of patient care are used in continually improving treatment for knee problems.
For more information about physical therapy and research at Shelbourne Knee Center, call 888-FIX-KNEE.
Reference
- Eaton S. Effect of Knee Range of Motion on Return to Full Quadriceps strength at 1 year Post-op Following Anterior Cruciate Ligament Reconstruction with Contralateral Patellar Tendon Graft. Presented at American Physical Therapy Association Combined Sections Meeting, January 2019 and Community Health Network 4th Annual Multidisciplinary Symposium, University of Indianapolis, May 2019.