A mucoid cyst is a small, fluid-filled sac that typically appears near the end joint of a toe, often near the base of a toenail. These cysts are benign but can cause discomfort or lead to changes in the nail, such as ridging or thinning, if they press against the nail matrix.
Mucoid cysts are usually associated with degenerative joint changes, particularly osteoarthritis. They form when joint fluid escapes through a weakened joint capsule and collects under the skin. Repeated pressure or trauma to the area can also contribute to their development.
These cysts present as smooth, round, often translucent bumps near the nail or toe joint. They may feel firm or jelly-like and can sometimes rupture or leak fluid. Diagnosis is typically made by physical examination. Your foot specialist may use light transillumination (shining a light through the cyst) to confirm it’s fluid-filled, and in some cases, imaging may be ordered to evaluate underlying joint health.
