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Imaging Characteristics of the Proximal Lateral Collateral Ligament of the Knee: Findings on Ultrasound and MRI With
Anna L Falkowski1,2, Jon A Jacobson1, Girish Gandikota1
1Department of Radiology, University of Michigan, Ann Arbor, Michigan.
Objectives:
Determine prevalence of increased signal intensity of the lateral collateral ligament (LCL) of the knee on MRI and decreased echogenicity on ultrasound, and compare with cadaveric histologic evaluation.
Methods:
After IRB approval of this prospective study with informed consent, patients having knee MRI were additionally evaluated with ultrasound. Signal intensities of LCL on MRI (low, intermediate, high), echogenicity at ultrasound (hyperechoic, hypoechoic, anechoic), and extent of findings were assessed. Descriptive statistics, Wilcoxon signed ranked test, and intraclass correlation coefficient (ICC) were calculated. Two cadaveric knees were imaged with MRI and ultrasound, including histologic LCL evaluation.
Results:
Seventy-three subjects were included (39 males, 34 females; mean age 48 ± 14 years) with 77 knee examinations. On MRI, low, intermediate, and high signals were present in 21% (16/77), 75% (58/77), and 4% (3/77), respectively. On ultrasound, echogenicity was assessed as hyperechoic, hypoechoic, and anechoic in 62% (48/77), 38% (29/77), and 0% (0/77), respectively. Mean length of increased signal was 8.6 mm (±4.9) on MRI, and 6.5 mm (±4.8) on ultrasound. The ICC showed a good to excellent intermodality reliability (0.735-0.899) without statistically significant difference for interreader measurements (P = .163-.795). Histology evaluation showed transition of ligament fibers to fibrocartilage at its insertion with increased connective tissue mucin corresponding to MRI and ultrasound findings.
Conclusions:
Increased signal intensity of the proximal LCL on ultrasound and MRI is common and corresponds to normal connective tissue mucin.
Insights
Increased signal intensity in the proximal lateral collateral ligament (LCL) on MRI and ultrasound is common. This finding often represents normal connective tissue, as confirmed by cadaveric evaluation.
Area of Science:
- Orthopedics
- Radiology
- Histopathology
Background:
- The lateral collateral ligament (LCL) is crucial for knee stability.
- Imaging findings of the LCL can be challenging to interpret.
- Understanding the imaging characteristics of normal LCL is essential for accurate diagnosis.
Purpose of the Study:
- To determine the prevalence of increased signal intensity of the LCL on MRI and decreased echogenicity on ultrasound.
- To compare these imaging findings with cadaveric histologic evaluation.
- To establish the correlation between imaging and histological findings of the LCL.
Main Methods:
- Prospective study involving knee MRI and ultrasound evaluations.
- Assessment of LCL signal intensity on MRI (low, intermediate, high) and echogenicity on ultrasound (hyperechoic, hypoechoic, anechoic).
- Comparison with histologic evaluation of LCL in cadaveric specimens.
Main Results:
- Seventy-seven knee examinations were analyzed.
- MRI showed low, intermediate, and high signals in 21%, 75%, and 4% of cases, respectively.
- Ultrasound revealed hyperechoic and hypoechoic findings in 62% and 38% of cases, respectively.
- Good to excellent intermodality reliability (ICC 0.735-0.899) was observed.
- Histology confirmed that increased signal/decreased echogenicity corresponds to normal connective tissue mucin.
Conclusions:
- Increased signal intensity of the proximal LCL on both MRI and ultrasound is a common finding.
- These imaging findings are frequently associated with normal connective tissue mucin.
- The study validates the correlation between imaging and histological characteristics of the LCL.
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