Measuring rotator cuff thickness is not easy; using the ultrasound probe (linear) on a circular surface (humeral head), may create lots of artifacts. What in Mri is called “magic angle”, with ultrasound imaging is the “anisotropy” and can be a source of interpretation error for inexperienced practitioners. Normal thickness of a rotator cuff goes from 2.5-3 mm to 6.5-7 mm, depending on anthropometric characteristics of each subject. Before every examination try to think at these important variabilities: how old is the patient? Male or female? Any kind of professional or sport activity? Recent trauma? Hyperactivity and no-activity make damages both. I always remind you to perform a comparative evaluation with the contralateral shoulder. A common mistake is to start the measurement directly from the cortical bone. Pay attention… before the tendon attachment you’ll find two important layers: cartilage and joint capsule. Take always in mind and count every time all the layers. Starting from the bone we have:

1 – cortical surface –
2 – cartilage
3 – joint capsule
4 – rotator cuff
5 – bursa (a hyperechoic line if synovial fluid is absent)
6 – deltoid muscle deep aponeurosis
7 – deltoid muscle
8 – deltoid muscle superficial aponeurosis 
9 – subcutaneous tissue
10 – cutis

Incorrect scan (left) – Correct scan (right)

To find the right postion, take the acromion as a landmark and put the probe just below as seen in the video at the bottom of the page.