Delaying paediatric knee operations may lead to an increased risk of complications in later life.
A new report from scientists at the University of Texas Southwestern Medical Center in Dallas found that anterior cruciate ligament surgery needs to be conducted within 150 days of the injury if it is to be at its most effective.
Doctors explained the likelihood of medial meniscus or chondral injuries increased the longer the operation was postponed.
Other factors were also found to be important.
"Our data demonstrates patient weight over 143 lbs (65 kg) to be associated with an increased rate of medial and lateral meniscal tears at the time of surgery," said the report's senior author Philip Wilson.
The researchers hope the findings may help healthcare staff improve their counselling of patients and families in the future.
Another recent scientific study found that five per cent of Americans now have prosthetic knees.