People who have had a knee reconstruction following trauma may be susceptible to osteoarthritis sooner than currently thought, according to new MRI findings at 1 year after anterior cruciate ligament reconstruction.

Almost a third of people studied had some evidence of early osteoarthritis (OA) at that early time point, challenging “existing dogma that degenerative joint disease does not become apparent for years post-ACLR,” reported Dr. Kay Crossley of the University of Queensland in Brisbane, Australia ( Arthritis Rheumatol. 2015 Feb. 18 [doi:10.1002/art.39005] ).

However, as they did not have access to preoperative images, they could not rule out that some OA features may have been preexisting and not related to knee trauma, they said.

“This is a sample that was taken after the injury and after the reconstruction, so they truly don’t know that what they’re finding is as a result of even the injury, surgery, or the meniscal damage or meniscal resection they had done at the time,” Dr. David J. Hunter, a leading OA expert from Sydney (Australia) University, said when asked to comment on the study’s findings.

“It may well be that these were people that had some underlying structural damage,” he added.

The researchers noted that radiographic knee OA was thought to be as high as 50%-90% a decade after anterior cruciate ligament reconstruction (ACLR). The issue is particularly important because ACL injuries typically occur in younger adults who are then prone to developing knee OA before they reach 40 years, they said.

“Early detection of knee OA after ACLR may permit early intervention such as load management, which is likely to be more effective prior to the development of advanced disease,” they wrote.

Their study included 111 patients aged 18-50 years who had undergone single-bundle hamstring-tendon autograft ACLR 1 year earlier.

MRI scans of their knees were compared with 20 uninjured asymptomatic matched controls. The researchers used the MRI Osteoarthritis Knee Score (MOAKS) to score specific OA features because the more recent Anterior Cruciate Ligament Osteoarthritis Score (ACLOAS) had not been published at the time of their study.

Results showed that 34 (31%) patients had MRI-defined knee OA following an ACLR a year earlier.

MRI-OA features were most frequently found in the patellofemoral compartment, particularly the medial femoral trochlea, a potentially underrecognized site of knee pathology following reconstruction, the researchers said.

Pathology in the patellofemoral joint included not only “early” features of OA, such as bone marrow lesions and partial-thickness cartilage loss, but also frank osteophytes on MRI, they noted.

None of the uninjured control knees had MRI-defined patellofemoral or tibiofemoral OA.

The authors acknowledged that a lack of access to preoperative knee images limited the conclusions they could reach in their study, but they noted that MRI-OA features were rarely seen in the small sample of uninjured matched control knees.

“Combined with the observation that six times as many reconstructed knees had radiographic osteophytes than uninjured contralateral knees, these findings suggest that knee trauma and/or reconstruction was strongly implicated in the development of OA features,” they wrote.

Another limitation that the authors acknowledged was that the MRI definition of OA was relatively new and was likely to be refined as the understanding of OA pathology evolved.

Dr. Hunter, who was the lead investigator involved in developing the MOAKS, agreed that the definition needed more validity and testing.

“This is the third study that uses that definition, and I do think that long-term clinical implications of what MRI definition means is unknown,” he said. “The challenge that we have is that we do kick up a lot of abnormalities, and we don’t truly know what the long-term clinical implications of those abnormalities are at this point.”

“There are a lot of problems with the way this study has been done, but I do think it is really helpful that it highlights how important injury is with regards to predisposing to early OA.”

“It’s something that a lot of people don’t really highlight or pay attention to,” he said.

The study was partly funded by the Queensland Orthopaedic Physiotherapy Network, a University of Melbourne Research Collaboration grant, and University of British Columbia’s Centre for Hip Health and Mobility via the Society for Mobility and Health. One study author is president of Boston Imaging Core Lab, LLC, and is a consultant to Merck Serono, Sanofi-Aventis, Genzyme and TissueGene. No other authors declared conflicts of interest.