Bursitis is a painful condition that affects the small, fluid-filled sacs – called bursae – that cushion the bones, tendons, and muscles near your joints. Bursitis occurs when bursae become inflamed. The most common locations for bursitis are in the shoulder, elbow, and hip. But you can also have bursitis by your knee, heel, and the base of your big toe. Bursitis often occurs near joints that perform frequent repetitive motion.
If you have bursitis, the affected joint might feel achy or stiff, hurt more when you move it or press it, or look swollen and red.
Bursitis, Mayo Clinic (Aug. 12, 2017), https://www.mayoclinic.org/diseases-conditions/bursitis/symptoms-causes/syc-20353242