Bone shape changes over two years following acute anterior cruciate ligament injury: Reconstructed vs non-reconstructed knees.

OBJECTIVE

To determine bone shape changes over two years after acute anterior cruciate ligament (ACL) injury and to compare knees treated with ACL reconstruction (ACLR) vs no ACLR.

DESIGN

We used prospective data involving 129 young adults (46 ​% female, mean age 25 years) with recent ACL injury from a subcohort within the prospective multicenter NACOX study. Patients were treated according to Swedish guidelines with supervised rehabilitation before considering ACLR. 3D MR images obtained at baseline, 3-, 6-, 12, and 24-months post-injury were assessed for changes in the femur and tibia bone surface area using active appearance models. We used a linear mixed-effects model adjusted for age, sex, body mass index, and pre-injury Tegner physical activity level.

RESULTS

We observed growth in bone areas over the first two years, particularly in the medial femur and medial tibia, with an average relative increase of 1.28 ​% (95 ​% CI 0.67 ​%, 1.88 ​%) and 1.04 ​% (0.44 ​%, 1.65 ​%), respectively. The lateral femur also showed growth, with an increase of 1.15 ​% (0.55 ​%, 1.75 ​%). We found little differences comparing ACLR patients to non-ACLR patients, adjusted relative percentage differences: medial femur, 0.01 ​% (95 ​% CI: 0.9 ​%, 1.1 ​%); medial tibia, -0.03 ​% (-1.2 ​%, 0.7 ​%); lateral femur, 0.04 ​% (-0.6 ​%, 1.4 ​%); and lateral tibia, -0.11 ​% (-2.1 ​%, -0.1 ​%).

CONCLUSION

After acute ACL injury, there is a growth primarily in the medial femoral and tibial condyles. The bone shape changes could hypothetically be a response to altered biomechanical conditions and may precede the development of knee OA.