Flexor carpi ulnaris tendinopathy: ultrasound in the dog
4-year-old dog that competes in lure coursing, with intermittent right forelimb lameness after exercise and a painful soft tissue thickening just proximal to the accessory carpal bone. Longitudinal ultrasound of the flexor carpi ulnaris insertion (the accessory carpal bone, with its acoustic shadow, is on the left):
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How do you interpret the circled area?
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A. Hypoechoic area without fibrillar pattern: insertional tendinopathy
Correct. The tendon is thickened, its two heads cannot be told apart and there is a hypoechoic area at the insertion with complete loss of fibre alignment. This is flexor carpi ulnaris tendinopathy, typical of sporting dogs.
B. Anisotropy artefact: normal tendon with the probe tilted
Anisotropy causes hypoechogenicity when the beam is not perpendicular to the fibres, but it disappears when the angle is corrected. Here the tendon is also thickened and painful, which confirms a real lesion.
C. Tendon mineralisation with posterior acoustic shadowing
Mineralisation would appear as a hyperechoic focus with acoustic shadowing. The marked area is hypoechoic and casts no shadow; the only shadow is that of the accessory carpal bone.
D. Complete tendon rupture with retracted ends
A complete rupture would show a gap in the tendon with separated ends and a space filled with fluid or haematoma. Here the tendon is continuous, although thickened with disorganised fibres.
lightbulb Key takeaway
A healthy tendon is hyperechoic with a parallel fibrillar pattern on longitudinal scans. Thickening, hypoechogenicity and loss of fibre alignment indicate tendinopathy. Keep the probe perpendicular to avoid anisotropy and always compare with the contralateral limb.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.