Thumb osteoarthritis – also known as basal joint or CMC osteoarthritis – affects the carpometacarpal (CMC) joint at the base of the thumb. This joint enables the wide range of thumb movements that gripping, pinching and grasping depend on. Over time, the cartilage cushioning the ends of the bones in this joint can deteriorate. As the cartilage wears away, the bones may rub directly against each other, causing pain, swelling and reduced motion.

Thumb osteoarthritis is particularly prevalent among women over 40, although it can affect anyone. Factors such as joint overuse, previous injuries or a genetic predisposition can increase the risk of developing it. Because the thumb, wrist and forearm work together in every grip, the same repetitive loading can also irritate the tendons on the outside of the elbow, as seen in tennis elbow.

For anyone in sports or activities that demand a strong grip and fine motor control, thumb osteoarthritis can be particularly debilitating. The pain and stiffness can hinder performance in sports such as tennis, golf or climbing, where thumb strength and flexibility are crucial. Even routine tasks such as opening jars, turning doorknobs or writing can become challenging.

Early symptoms include discomfort during or after use of the thumb, a decrease in grip strength or noticeable swelling at the base of the thumb. As the condition progresses, a bony prominence may develop over the joint and the thumb may gradually shift out of its normal position, further limiting function.

Recognising these signs early and seeking appropriate treatment helps manage symptoms and maintain an active lifestyle. Alongside medical treatment, a thumb and wrist support can relieve the joint during everyday tasks and training.