Acute non-contact anterior cruciate ligament tears are associated with relatively increased vastus medialis to semimembranosus cross-sectional area ratio: a case-control retrospective MR study

Skeletal Radiol. 2017 Nov;46(11):1469-1475. doi: 10.1007/s00256-017-2709-3. Epub 2017 Jul 15.


Objective: Hamstring muscle deficiency is increasingly recognized as a risk factor for anterior cruciate ligament (ACL) tears. The purpose of this study is to evaluate the vastus medialis to semimembranosus cross-sectional area (VM:SM CSA) ratio on magnetic resonance imaging (MRI) in patients with ACL tears compared to controls.

Materials and methods: One hundred knee MRIs of acute ACL tear patients and 100 age-, sex-, and side-matched controls were included. Mechanism of injury, contact versus non-contact, was determined for each ACL tear subject. The VM:SM CSA was measured on individual axial slices with a novel method using image-processing software. One reader measured all 200 knees and the second reader measured 50 knees at random to assess inter-reader variability. The intraclass correlation coefficient (ICC) was calculated to evaluate for correlation between readers. T-tests were performed to evaluate for differences in VM:SM CSA ratios between the ACL tear group and control group.

Results: The ICC for agreement between the two readers was 0.991 (95% confidence interval 0.984-0.995). Acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.44 vs. 1.28; p = 0.005). Non-contact acute ACL tear patients have an increased VM:SM CSA ratio compared to controls (1.48 vs. 1.20; p = 0.003), whereas contact acute ACL tear patients do not (1.23 vs. 1.26; p = 0.762).

Conclusion: Acute non-contact ACL tears are associated with increased VM:SM CSA ratios, which may imply a relative deficiency in hamstring strength. This study also demonstrates a novel method of measuring the relative CSA of muscles on MRI.

Keywords: ACL; ACL tear; Anterior cruciate ligament; Anterior cruciate ligament tear; Hamstring; Quadriceps; Semimembranosus; Vastus medialis.

MeSH terms

  • Acute Disease
  • Adult
  • Anterior Cruciate Ligament Injuries / diagnostic imaging*
  • Case-Control Studies
  • Female
  • Hamstring Muscles / diagnostic imaging*
  • Hamstring Muscles / injuries
  • Hamstring Muscles / pathology*
  • Humans
  • Image Interpretation, Computer-Assisted
  • Magnetic Resonance Imaging / methods*
  • Male