March 31, 2014
2 min read

Bone shape in ACL injured knee joint changes rapidly after injury

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

The shape of the bones in an ACL-injured knee joint undergo rapid change measured as an increase of bone area during the first 2 years after an ACL tear, according to study results presented at the Orthopaedic Research Society Annual Meeting.

“In order to develop interventions, we need to identify those with osteoarthritis (OA) as early as possible,” Richard Frobell, PhD, of Lund University in Sweden, stated in a press release.

Researchers randomly assigned 121 young active adults with an acute ACL tear in a previously un-injured knee to either rehabilitation plus early ACL reconstruction or rehabilitation plus the option of having a delayed ACLR if needed. MRIs were available for 111 participants at the 3-year follow-up and for 108 patients at the 2-year and 5-year follow-ups.

Using active appearance models, researchers automatically segmented femur, tibia and patella bone surfaces from the MRIs. Bone area regions were calculated from the segmentations for the medial and lateral femur, tibia and patella. Researchers used the Osteoarthritis Initiative to identify 167 MRIs from the right knee with no signs of radiographic OA at baseline and 2 years. Change was a percent difference over time with positive values indicating increased bone area.

Researchers found significant changes of bone shape for all regions of the knee for both investigated time intervals with increased areas found over time. The change mainly occurred during the first 2 years after injury with the smallest increase in the lateral trochlea femur and the largest increase in medial femur. Smaller significant changes occurred during the subsequent 3-year period with the smallest increase occurring in the lateral trochlea femur with the largest increase in the medial and lateral patella. During the overall 5-year period, researchers found the largest increase in bone area in the medial and lateral patella. Study results showed small or no significant change in patients without radiographic OA at 2 years.

“Our research aims to identify early changes of the shape of the bones in the knee joint. The next step is to use our cohorts on knee injury to identify risk factors of osteoarthritis and to test different methods as proxies for early disease,” Frobell said.


Frobell RB. Significant change of bone shape occur in knees of acutely ACL injured individuals over the first five years after injury. Presented at: Orthopaedic Research Society Annual Meeting. March 15-18, 2014; New Orleans.

Disclosure: Frobell has no relevant financial disclosures.