Anargyros T. Karatrantos, Aikaterini I. Sideri, Pagona G. Gouletsou, Christina G. Bektsi, Mariana S. Barbagianni
Background
Canine stifle disorders—particularly cranial cruciate ligament rupture—are major causes of hindlimb lameness, requiring accurate diagnostic imaging. Despite the availability of CT and MRI, clinical use may be limited by cost or accessibility, positioning ultrasonography as an important alternative. This review synthesizes literature on ultrasound applications for stifle evaluation, including B-mode, Doppler, contrast-enhanced ultrasound (CEUS), and elastography, to clarify each modality’s diagnostic value and limitations. The rationale is grounded in the need for dynamic, affordable imaging capable of characterizing soft tissue, blood flow, and mechanical changes within the stifle joint.
Methods
The authors conducted a narrative review with literature searches in July 2024 and an update in May 2025. Databases included PubMed (MEDLINE), Web of Science, and Google Scholar. Search terms focused on ultrasonography and canine stifle structures. Included studies described sonographic examinations or stifle-related anatomy, with no restrictions on publication year. Exclusion criteria encompassed articles not producing ultrasound images, reports on therapeutic ultrasound, referral-based ultrasound use, and non-English/German publications. Relevant anatomy textbooks were also incorporated. The review integrates data from human, canine, equine, bovine, and experimental animal studies to contextualize ultrasound methodologies.
Results
The review details normal and pathological sonographic features of muscles, tendons, ligaments, bone, menisci, peripheral nerves, and arteries in the canine stifle. B-mode ultrasound reliably identifies patellar ligament changes, joint effusion, synovitis, osteophytes, cartilage defects, meniscal swelling, and fractures. Doppler modalities detect joint neovascularization in inflammatory and degenerative conditions, with power Doppler and PW Doppler providing hemodynamic information. CEUS enhances sensitivity for early inflammatory vascular changes and soft-tissue perfusion, outperforming Doppler in early neovascularization. Elastography methods—strain and shear-wave—quantify tissue stiffness, distinguishing healthy from diseased patellar ligaments and offering insight into mechanical properties altered by CCL disease. Combined multimodal ultrasound provides dynamic assessment that can guide interventions and monitor healing.
Limitations
Limitations arise primarily from ultrasound's dependence on operator expertise, equipment quality, and anatomical accessibility. High-frequency probes have shallow penetration, limiting visualization of deep structures. Artifacts and anisotropy may reduce diagnostic sensitivity if not recognized. Comparative limitations in meniscal assessment occur in cases of fibrosis, advanced osteophytosis, or previous surgery. CEUS is invasive, costlier, time-consuming, and restricted to a single plane per acquisition. Elastography findings vary by technique, joint angle, and patient positioning, complicating cross-study comparison.
Conclusions
Ultrasound—particularly when incorporating Doppler, CEUS, and elastography—offers a versatile, accessible, and dynamic imaging platform for canine stifle evaluation. While not a replacement for CT or MRI, it provides valuable diagnostic insights into soft tissue integrity, neovascularization, biomechanics, and joint pathology. B-mode remains essential for structural assessment, Doppler and CEUS augment vascular evaluation, and elastography supports quantification of mechanical tissue properties. The authors emphasize adopting modality selection based on the structure of interest and the clinical question, noting that multimodal ultrasound can significantly improve diagnostic accuracy and clinical decision-making in veterinary orthopedics.
(A) Schematic illustration of the dog’s stifle joint, depicting the lateral aspect. (B) Ultrasonographic image of a normal stifle joint in a dog, captured from the lateral view. (C) Ultrasonographic image of the stifle joint in a dog with patellar luxation, with an arrow indicating the presence of anechoic fluid, which suggests effusion. The images were obtained using an Esaote MyLab™ Sigma ultrasound machine with a linear probe (L 4-15) (Esaote, Genoa, Italy) operating at a frequency of 12 MHz and a depth of 2 cm. (Ultrasound images: A. Karatrantos.)
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