Experts have detailed a possible link between the Zika virus and a severe joint condition in babies.

Zika infection of pregnant women has been associated with the birth of babies with abnormally small heads and brain damage.

Zika is spread via mosquitoes and by sexual contact.

Researchers in Brazil have reported on the cases of seven children with a condition called arthrogryposis, which causes joint deformities at birth, particularly in the arms and legs.

The team based in Recife, the Brazilian city at the centre of the Zika epidemic, decided to investigate the possible causes of the joint deformities.

Experts detailed brain and joint images of seven children with arthrogryposis and a diagnosis of congenital infection, presumably caused by the Zika virus.

Their study, published in the BMJ, said the arthrogryposis seen in the babies was "likely to be of neurogenic origin".

The researchers suggest the condition might be related to the way motor neurons carry signals to the unborn baby's muscles, or to problems with the arteries and veins.

The current epidemic began in Brazil last year. The virus's link to microcephaly was deemed to be a public health emergency of international concern by the World Health Organization earlier this year.