Objective: Our purpose was to study the natural course of bone bruises in posttraumatic knees and to describe possible determinants of this course.
Subjects and methods: Prospective MRI follow-up data were gathered for patients with bone bruises after sustained knee trauma. Follow-up ceased when the bone bruise could no longer be discerned or after 1 year of follow-up. For each patient we studied the relationships between time to healing of all bone bruises and the explanatory variables age, sex, obesity, workload, sports load, number of bone bruises, osteoarthritis, and concomitant knee lesions using survival analyses. We also investigated the relationships between resolution of individual bone bruises and lesion type, size and location, and the explanatory variables at 6 months and at 12 months separately, using logistic regression analyses for repeated measurements and generalized estimating equations.
Results: In 80 patients, 157 bone bruises were found. The estimated median healing time was 42.1 weeks. Healing was prolonged in patients having a higher number of bone bruises and in the presence of osteoarthritis. Resolution of individual bone bruises was prolonged in the presence of osteoarthritis and greater age. Reticular lesions were less likely to be present after 6 months than other bone bruise types. None of the remaining tested variables had prognostic value.
Conclusion: Median healing time of bone bruises is 42.1 weeks. Prognosis is particularly influenced by the presence of osteoarthritis. Age, type of bone bruise, and number of bruises also have prognostic value.