burs

Burs is a term that can refer to different structures in medicine and botany. In anatomy, bursae are small, fluid-filled sacs surrounding joints and tendons that reduce friction. In botany, a burr, plural burs, is a seed or fruit with hooks or bristles that cling to fur or fabric to assist dispersal.

Anatomical bursae are lined by a synovial membrane and contain a small amount of synovial fluid. They act as cushions between bones and soft tissues to allow smooth movement. Common sites include the subacromial bursa in the shoulder, the olecranon bursa at the elbow, and the prepatellar and infrapatellar bursae around the knee. When a bursa becomes irritated or inflamed, the condition is called bursitis. Causes include repetitive motion, overuse, trauma, infection, and inflammatory diseases. Symptoms typically include localized pain, swelling, warmth, and reduced range of motion. Diagnosis is clinical and may be aided by ultrasound or MRI; treatment ranges from rest and NSAIDs to drainage or injections.

Botanical burs are dry seed cases with hooked or spiny projections that attach to fur, feathers, or clothing, aiding dispersal via animal carriers. They occur in many plant groups, including burdock and cocklebur, as well as various grasses. Besides spreading seeds, burs can irritate skin or fabrics and are often removed by brushing, washing, or careful detachment. Ecologically, their structure promotes epizoochory, the transport of seeds by external vectors, which helps plants colonize new areas. In agriculture and horticulture, burs can present cleaning challenges and may require mechanical or manual removal.