[Relevance of different sequences in MRI-detected subchondral bone damage of the knee joint and possible therapeutic options].

With the advent of magnetic resonance imaging (MRI) after knee injuries interest has focussed on the clinical relevance of different concomitant osseous damage. Different MRI- sequences reveal varying characteristics of such lesions. Prospective data of 69 patients with MRI-detected sub-acute subchondral fractures or bone bruises according to the classification of Mink was recorded. Function, symptoms (Noyes) and activity (Tegner) were assessed at the time of first MRI and 7,4 months later including a follow-up MRI using T 2-weighted fat saturated (fs) fast-spin-echo-sequences (FSE), T 1-weighted spin echo (SE) sequences, Proton-density-weighted spin echo-sequences (SE) and T 2-weighted (fs) gradient-echo-sequences. The patients were divided in 4 groups: patients with subchondral fracture and patients with pure bone bruise subdivided in patients with and without intraarticular knee lesions. Bone bruises were diagnosed in 44 cases, subchondral fractures in 25 patients. Patients without intra-articular pathology had significantly poorer function at the time of MRI with subchondral fractures, but not in the sub-group with intra-articular damage. Symptoms were not significantly different in both groups at this time. At 7,4 months both sub-groups with fractures had a lower level of function compared to patients with bone bruises, activity score and symptoms showed poorer results in the group without intraarticular lesion (p = 0,01 for all scores). T 1- weighted spin echo (SE) sequences revealed to be the most important tool to differentiate the various lesions. Hints for a modification of rehabilitation avoiding axial forces in case of subchondral fractures might be the use of isokinetics using open kinetic chain instead of closed kinetic chain or orthosis with relief of the affected compartment.