Posttraumatic Bone Marrow Lesion Volume and Knee Pain Within 4 Weeks After Anterior Cruciate Ligament Injury.

CONTEXT:   After an anterior cruciate ligament (ACL) injury, a majority of patients have a traumatic bone marrow lesion (BML, or bone bruise). The clinical relevance of posttraumatic lesions remains unclear.

OBJECTIVE:   To explore the cross-sectional associations between traumatic BML volume and self-reported knee pain and symptoms among individuals within 4 weeks of ACL injury.

DESIGN:   Cross-sectional exploratory analysis of a randomized clinical trial.

SETTING:   Orthopaedic departments at 2 hospitals in Sweden.

PATIENTS OR OTHER PARTICIPANTS:   As part of a randomized trial (knee anterior cruciate ligament nonoperative versus operative treatment [KANON] study), 121 young active adults (74% men, age = 26 ± 5 years, height = 1.8 ± 0.1 m, weight = 76 ± 13 kg) with an ACL tear were studied.

MAIN OUTCOME MEASURE(S):   The BML volume in the proximal tibia and distal femur was segmented using magnetic resonance images obtained within 4 weeks of injury. A radiologist evaluated the presence of depression fractures on the images. Pain and symptoms of the injured knee (Knee Injury and Osteoarthritis Outcome Score [KOOS] pain and symptoms subscales) were obtained the same day as imaging. We used linear regression models to assess the associations.

RESULTS:   Most knees had at least 1 BML (96%), and the majority (57%) had a depression fracture. Whole-knee BML volume was not related to knee pain for the entire cohort (β = -0.09, P = .25). Among those without a depression fracture, larger whole-knee BML volume was associated with increased knee pain (β = -0.46, P = .02), whereas no association was found for those with a depression fracture (β = 0.0, P = .96). Larger medial (β = -0.48, P = .02) but not lateral (β = -0.03, P = .77) tibiofemoral BML volume was associated with greater pain. We found no association between BML volume and knee symptoms.

CONCLUSIONS:   We confirmed the absence of relationships between whole-knee BML volume and pain and symptoms within 4 weeks of ACL injury. Our findings extend previous reports in identifying weak associations between larger BML volume in the medial compartment and greater pain and between BML volume and greater pain among those without a depression fracture.