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Updated: Jun 9, 2026
Early Weight-Bearing Rehabilitation Protocol After Anterior Cruciate Ligament Reconstruction
Published on: March 1, 2024
Changes in Muscle Volume Asymmetries Among Lower Extremity Muscles From Baseline Through 12 Months After Anterior
Keith A Knurr1,2,3, Mikalyn T DeFoor4, Matthew Blomquist1,2
1Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Background:
Recovery of quadriceps muscle volume and function is a primary rehabilitation focus after anterior cruciate ligament reconstruction (ACLR). However, limited evidence exists on the recovery of other lower extremity muscles. Early activity limitations and persistent postoperative biomechanical alterations may contribute to volume changes in lower extremity muscles.
Purpose/Hypothesis:
The purpose of this study was to characterize lower extremity muscle volume changes from preoperative baseline to 12 months post-ACLR. It was hypothesized that the quadriceps would show the largest, most persistent atrophy. It was further hypothesized that other muscles would show atrophy early post-ACLR but that most would recover to preoperative levels by 12 months except for the gastrocnemii, which have previously demonstrated long-term atrophy.
Study Design:
Case series; Level of evidence, 4.
Methods:
A total of 25 patients (mean age, 26.8 ± 9.0; 52% female) undergoing ACLR with quadriceps tendon autograft had bilateral lower extremity magnetic resonance imaging scans within 9 days prior to ACLR as well as 3 and 12 months post-ACLR. Muscle volumes for 34 bilateral muscles were determined using an automated segmentation algorithm. Volume was normalized to height-mass product. Standardized mean differences (SMDs) and paired t tests assessed between-limb asymmetries. Linear mixed-effects models with a fixed effect of time and random effect for patient assessed longitudinal changes.
Results:
Significant operative limb deficits were present in 6 of 34 (17.6%) muscles preoperatively, 16 of 34 (47.1%) at 3 months, and 10 of 34 (29.4%) at 12 months. Vasti deficits were the most pronounced and persistent (SMD: preoperative, 0.4-0.6; 3 months, 1.1-1.2; 12 months, 0.9; all P < .03). Significant deficits also persisted in the gastrocnemii (SMD: 0.4-0.5 at 12 months; P < .03). The gluteus maximus of the operative limb was significantly larger at 12 months (SMD: 0.18; P = .045).
Conclusion:
Operative limb muscle volume deficits were greatest at 3 months post-ACLR. Significant deficits of the quadriceps and gastrocnemii persisted at 12 months post-ACLR, while the operative limb gluteus maximus was larger than the nonoperative limb at 12 months.