A knee injury expert has warned amateur footballers not to pile on the festive pounds before they return to action in the new year.

Professor David Barrett, a knee and sports injury specialist at Southampton General Hospital, said he expected to see an ''avalanche'' of injuries in January as overweight and unfit players put on their pads and boots after an over-indulgent Christmas.

He said the problems mostly affect men in their mid-30s and mainly those in veteran leagues who ''have the mindset of a teenager but the fitness of Father Christmas''.

''We see an extra 10 to 12% of knee and ankle injuries in the first two or three weeks after the New Year celebrations as middle-aged men take to the pitch without any prior preparation,'' he said.

''This period is a real challenge for those who have no residual fitness but dive straight into action at full pace on icy or wet surfaces after solid days of eating unhealthily, festive drinking and staying indoors, inactive.

''They really struggle and, as a result, make late tackles, twist or turn awkwardly, or tire themselves so much their minds and bodies don't work in tune, often resulting in cartilage, ligament or bone damage.''

Prof Barrett also urged caution among players drafted in as a result of team shortages because of colds and flu throughout the winter.

He said: ''We also find this a difficult time for those men who play sporadically.

''They are often really unfit but get the chance to play due to illness. When they do, they are simply out of their league.''

However, these problems could be avoided with light but regular exercise, he continued.

''I think it's fantastic that middle-aged to older men want to keep up their sport and it's important that they do.

''But they won't be able to do that if they inflict a serious but avoidable injury on themselves,'' he said.

''I would advise them to be sensible about their fitness and ensure they participate in some light training or exercise regularly over Christmas and New Year so they can take to the field at less risk of unnecessary injury.''