SAN DIEGO – In the majority of patients with knee osteoarthritis, the baseline volumes of associated bone marrow lesions change substantially within 6 to 12 weeks of diagnosis, judging from the findings of an ongoing drug study.
The findings suggest that volume changes – either decreases or increases as determined by magnetic resonance imaging – may help assess short-term fluctuations in joint damage.
"I think this may allow trials to be done with relatively smaller numbers of patients and briefer follow-ups," said the study’s lead author Dr. David Felson, professor of medicine and epidemiology at both Boston University and the University of Manchester (England).
A rapid marker for disease progress would be welcome; osteoarthritis (OA) is generally considered a slowly evolving disease "with glacial changes in cartilage morphology necessitating trials of potential treatments lasting 1-2 years," Dr. Felson said at the World Congress on Osteoarthritis.
"To the extent that they could be regarded as treatment targets, trials testing [bone marrow lesion] effects could avoid the usual prolonged structure modification trials," he said.
Bone marrow lesions (BMLs) are ill-defined, hyperintense lesions in subcortical bone detected during water-sensitive, fat-suppressed MRIs. Their presence indicates local bone damage and microfractures.
Recently, larger BMLs have been correlated with worse knee pain. Lesions have also been related to malalignment, risk of overlying cartilage loss, OA progression, and poor outcomes, Dr. Felson said.
He and his colleagues used axial and sagittal MRIs to assess BML volumes in patients with painful patellofemoral at baseline, 6, and 12 weeks. The patients were 40-70 years old, with a mean body mass index of about 30 kg/m2. Baseline median BML volumes were a bit over 2,000 mm3.
During the study, 23 of 35 assessed knees had a greater than 50% change in volume. Eight had a greater than 50% change in volume at 6 weeks only, 4 at 12 weeks only, and 11 at both 6 and 12 weeks. BMLs increased or decreased in roughly equal numbers of knees during the study.
Volumes have been known to change at 1 year follow-up; the finding that they do so in as little as 6 weeks is new.
In short, "I think it’s a good marker," Dr. Felson said.
The patients were all participating in a larger treatment trial; the results are still blinded, so it’s not yet possible to correlate treatment outcomes with volume changes.
"Wait for next year," Dr. Felson said.
The congress was sponsored by Osteoarthritis Research Society International. Dr. Felson said he has no disclosures. The study was funded by Arthritis Research UK.