A "bony bump" or a squared-off appearance at the base of the thumb where it meets the wrist.
There are several biological reasons why "mature thumbs" are a predominantly female experience:
Sharp or dull pain at the base of the thumb when opening jars, turning doorknobs, or pulling zippers.
Finding yourself dropping items or feeling a "grinding" sensation (crepitus) during movement. Managing the Pain: From Home Remedies to Specialist Care
Women generally have more flexible ligaments. While great for overall mobility, it can lead to instability at the base of the thumb (the "saddle joint"), causing the cartilage to wear down faster.
The "Saddle" Struggle: Understanding Thumb Pain in Mature Women
Research suggests that declining estrogen levels during and after menopause can weaken collagen, making joints more vulnerable to wear and tear.