FORT LAUDERDALE, FLA. – Symmetrical bilateral progression of knee osteoarthritis was a surprising result of a genetic study of people with hand osteoarthritis and their relatives.
“[This finding] indicates to me that there is probably a strong genetic factor for progression,” Dr. Virginia Byers Kraus said in an interview during a poster session at the World Congress on Osteoarthritis.
Dr. Byers Kraus and her associates studied 1,333 patients with hand osteoarthritis for a median of 3.8 years. Participants whose osteoarthritis progressed in either the medial or lateral compartment of one knee were significantly more likely to show progression in the same compartments of the other knee.
There are clinical implications to the findings. For example, “if you see these individuals [with hand osteoarthritis], if they have an affected knee, the other is likely to be affected with osteoarthritis and they are likely to progress in parallel,” said Dr. Byers Kraus, an internist in the division of rheumatology, Duke University Medical Center, Durham, N.C. “It's a probable prognostic factor for patients.”
What makes the conclusions “particularly intriguing” is that the knee progression symmetry was observed in this study of people with hand osteoarthritis, Dr. Byers Kraus said at the meeting, which was sponsored by the Osteoarthritis Research Society International.
The cohort came from the Genetics of Generalized Osteoarthritis (GOGO) study. In all, 79% were women and the mean age was 69 years. Researchers scored baseline and follow-up radiographs for changes in Kellgren-Lawrence grade, minimal joint space, presence of osteophytes, and joint space narrowing of the medial and lateral knee compartments. They also assessed at least two affected siblings with three-joint bilateral bony enlargements in their hands to assess any genetic correlations.
“In a cohort with hand osteoarthritis, they were more likely to have osteoarthritis [in other joints] if family members have hand osteoarthritis,” Dr. Byers Kraus said. And “when you have a patient with hand osteoarthritis and relatives with hand osteoarthritis, there is an increased likelihood of bilateral knee osteoarthritis.”
These findings support a strong genetic or constitutional risk for progression in knee osteoarthritis, Dr. Byers Kraus said.
The results also could have research implications, especially in studying people with osteoarthritis but in whom there is no progression, Dr. Byers Kraus said. This makes it difficult to assess the efficacy of a particular treatment compared with a control group. “This was responsible for the failure of a major trial on Actonel. Age, female gender, obesity–outside of these, we are not good at identifying definite progressors.”