Bone bruise in the acutely injured knee.

We used MRI to study the lesions in a consecutive group of 64 patients with an acute trauma of the knee and normal plain radiography during the winter season. Bone bruise was present in 35 of the patients, and these were referred to subsequent MRI 4 and 12 months later. After 4 months bone bruise was still present in 69% of the patients and after 12 months in 12%. Soft tissue lesions, for example, lesion in the meniscus, ACL rupture, or MCL lesion was present in 94% of the patients with bone bruise. Interobserver agreement varied from good to excellent. Soft tissue lesions are found in almost all patients with bone bruise, and these generally resolve 4-12 months after the injury. In the patients with no bone bruise the number of ligament injuries was lower.