Abstract: Objective To evaluate prospectively clinical significance and consequence of type Ⅰ bone bruise in acutely sprained knee. Methods 23 outpatients were selected, meeting our criteria from 2005 to 2008. All the injured knees were immobilized with gypsum for 4 to 6 weeks, and the knee complaints and MRI were followed up regularly.Results 18 patients were followed up, averaged 24 months, the bone bruise showed notable resolution in average 3 months and vanished in 6.7 months averagely; the knee pain alleviated obviously in about 4.8 months; 5 out of 9 cases, who were more than 45 years old, still complained knee pain and uncomfortable after 2 years.Conclusion Grade Ⅰ knee sprain can lead to bone bruise in condyles of femur or tibia, and knee immobilization should be given to avoid the further damage; the bone bruise may be a precursor of knee osteoarthritis for people older than 45 years.

Key words: knee sprain, bone bruise, clinical consequence