What does bursae mean?
Bursae are small, sac-like structures found throughout the human body, filled with a slippery fluid that allows tendons, muscles, and bones to glide smoothly over one another. The singular form is 'bursa', and the adjective describing them is 'bursal'. Humans have many of these cushions — particularly around major joints such as the shoulder, elbow, hip, and knee — where movement would otherwise create painful friction. Although healthy bursae go entirely unnoticed, they become medically significant when irritated or inflamed, a condition known as bursitis, which often results from repetitive motion, prolonged pressure, or injury. Because of this, the word appears chiefly in anatomy textbooks, medical reports, and sports-medicine contexts rather than everyday conversation. Etymologically it descends from Latin 'bursa', meaning purse or pouch, a fitting image for these little fluid-filled bags. Knowing the term helps patients understand diagnoses involving joint pain and swelling.
nounPlural of 'bursa': small fluid-filled sacs lined with synovial membrane that cushion friction between bones, tendons, and muscles around the joints of the body.
- Anatomical sense: fluid-filled sacs that reduce friction between moving structures at joints, such as the shoulder, hip, knee, and elbow.
"Inflammation of the bursae around the shoulder is a common cause of joint pain."
"The radiologist noted fluid in the bursae surrounding the patient's hip joint."
"Repetitive kneeling can irritate the bursae of the knee, leading to swelling and discomfort."
'Bursae' is itself the standard plural of 'bursa', following the Latin first-declension pattern; the anglicized plural 'bursas' occasionally appears but 'bursae' is strongly preferred in medical writing.
"Examination revealed swelling in two of the bursae around the knee."
Your body carries dozens of tiny built-in water balloons called bursae — and you only ever notice them when one gets angry.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of bursae
The word derives ultimately from Greek 'byrsa', meaning hide or leather, which passed into Latin as 'bursa' meaning a purse or pouch made of skin. Anatomists adopted the Latin word because a bursa resembles a small pouch of fluid. The same Latin root gave English several related words, including 'bursary' (a scholarship fund), 'disburse' (to pay out money), and 'reimburse' (to pay back), all built on the image of drawing from a purse.
Related word forms
How bursae is actually used
Strictly anatomical and medical register; used almost exclusively by clinicians, anatomists, and medical writers. Always treated as the plural of 'bursa'; the adjective form is 'bursal'.
Easily confused with bursae
A burse is a purse or pouch (historically for coins or ecclesiastical items), while bursae refers specifically to the anatomical fluid-filled sacs that cushion joints.