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. 2025 Jul;35(7):e70109.
doi: 10.1111/sms.70109.

Quadriceps Morphology 6- to 60-Months After Anterior Cruciate Ligament Tear

Justin M Losciale  1   2   3   4   5 , Bruce Lin  6 , Marine Theret  6 , Allyson M Schweitzer  7 , Matthew D Fliss  7 , Thomas Scarr  8 , Xian He Yan  1   2   9 , Navin Prasad  10 , Michael A Hunt  1   9 , Michael S Koehle  7   10 , Fabio M V Rossi  6 , Cameron J Mitchell  7 , Jackie L Whittaker  1   2   9
Affiliations

Quadriceps Morphology 6- to 60-Months After Anterior Cruciate Ligament Tear

Justin M Losciale et al. Scand J Med Sci Sports. 2025 Jul.

Abstract

The purpose of this study was to compare quadriceps morphology between legs and individuals with a first-time anterior cruciate ligament (ACL) tear and uninjured controls. This was an exploratory cross-sectional study. We enrolled participants who were aged 19-35 years, and 6-60 months after a first-time ACL tear as well as uninjured controls. Participants attended two sessions separated by a minimum of 7 days. Bilateral knee extensor concentric and eccentric strength and rate of torque development (RTD) were assessed at the first session, and bilateral vastus lateralis muscle biopsies were obtained at the second. Muscle fiber-type specific cross-sectional area (fCSA), fiber-type proportions, and extracellular matrix area were calculated. Between-limb and between-group differences were estimated using mixed-effects regression. 41 of 47 (87%) participants completed the study (n = 21 ACL, n = 20 control). ACL group participants were a median (range) of 23 months from injury, and 78% had undergone an ACL reconstruction. Uninjured group participants had greater knee extensor concentric strength (-39.3 Nm; 95% CI: -54.2, -20.5), eccentric strength (-30.2 Nm; 95% CI: -53.4, -11.6), and RTD (-0.16 Nm/ms; 95% CI: -0.33, -0.04). No between-group or between-limb differences in muscle fiber-type specific fCSA, fiber-type proportions, or extracellular matrix area were observed. Despite deficits in knee extensor muscle performance, no difference in vastus lateralis fiber-type specific CSA, fiber-type proportion, or extracellular matrix area was detected between individuals 6-60 months after an ACL tear and uninjured controls.

Keywords: atrophy; fiber types; fibrosis; muscle performance; quadriceps.

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Conflict of interest statement

Patient and Public Involvement: A physical therapist with 4 years' of clinical experience was involved in the design, conduct, reporting, and dissemination of this current study.

The authors declare no conflicts of interest. J.M.L. is an Associate Editor with the Journal of Orthopedic & Sports Physical Therapy Methods. M.S.K. is an editor with the Scandinavian Journal of Medicine & Science in Sports. J.L.W. is a Senior Editor with the Journal of Orthopedic and Sport Physical Therapy, Senior Associate Editor of the British Journal of Sports Medicine, Arthritis Society (Canada) Integrated Scientific and Medical Advisory Committee member, and Data Safety and Monitoring Committee member for the PIKASO trial. M.A.H. is a Data Safety and Monitoring Board Committee member for the Surgical Timing and Rehabilitation (STaR) for Multiple Ligament Knee Injuries (MLKI): A Multicenter Integrated Clinical Trial.

Figures

FIGURE 1
FIGURE 1
Representative muscle biopsy image. Image from an uninjured control, scale bar is 100 μm. Panel A: wheat germ agglutinin stain for ECM area, Panel B: type I fibers, Panel C: type IIa fibers, Panel D: type IIx fibers, Panel E: composite image (Type I = red, Type IIa = blue, Type IIa/x = Gray, ECM = Green). ECM, extracellular matrix.
See this image and copyright information in PMC

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