I injured my right thumb and I feel pain in the dorsal region of the metacarpophalangeal joint. what could be the reason for the pain and when should I see a doctor? (photo)

Thank you for your inquiry.

From the photographs, there appears to be some swelling and redness over the dorsal aspect of the metacarpophalangeal joint (MCPJ) of the right thumb. in the second photograph, it seems that the extension of the thumb is possible. In fact, the thumb is hyperextended at the MCPJ of the thumb which may indicate a normal variant of MCPJ laxity, commonly seen in young persons.

The structures which may have been injured over the dorsal aspect of the MCPJ and corresponding to the area of interest may be one or more of the following:

1. Subcutaneous tissue
2. Extensor Pollicis Brevis tendon
3. Dorsal MCPJ capsule
4. Dorsoradial ligament (DRL) of the MCPJ
5. The base of the proximal phalanx or head of the 1st metacarpal bone
6. The injury may be anything from a simple contusion or sprain to more serious conditions such as ligament tears or chondral (cartilaginous) damage.

A detailed clinical assessment and imaging of the thumb may be necessary to make an accurate diagnosis of the injured structures. Definitive treatment may then be instituted. I suggest that you see a Hand Surgeon as soon as you are able to.