High pain sensitization levels associated with greater knee pain progression

Subjects with low knee pressure pain thresholds had a 1.6-times higher risk of developing constant pain over 2 years.

Individuals with knee osteoarthritis who had higher levels of peripheral and central sensitization had a greater risk of pain progression from no or intermittent pain to chronic and persistent pain over time, according to results presented at a meeting.

“There are probably nervous system alterations which help explain why some people transition from having intermittent or acute pain to chronic, persistent pain. It is not necessarily solely what is going on in the arthritic joint,” Tuhina Neogi, MD, PhD, professor of medicine and epidemiology at Boston University School of Medicine and School of Public Health, told Orthopedics Today. “The severity and duration of what is going on in terms of pathology of the arthritic joint certainly contributes to pain, but the pain experience is being influenced by factors beyond just what is going on in the arthritic joint and these nervous system alterations likely play an important role in this transition.”

Measuring pressure pain threshold

Neogi and her colleagues measured pain sensitization by evaluating mechanical pressure pain thresholds at the wrist and patella in 1,951 subjects with knee osteoarthritis (OA) in the Multicenter Osteoarthritis Study (MOST) who did not have constant pain at baseline.

Lower pressure pain threshold (PPT) reflects higher pain sensitization, according to Neogi.

The subjects completed pain questionnaires at baseline and 2-year follow-up. Researchers used the knee-specific Intermittent and Constant OA Pain instrument to define pain patterns as no intermittent or constant pain, intermittent pain only, and constant pain with or without intermittent pain.

“We found being more sensitized at baseline was associated with greater risk of developing constant pain over 2 years,” Neogi said at the meeting.

Specifically, Neogi noted individuals with a low PPT at the knee had a 1.6 times higher risk of developing constant pain over 2 years compared with patients with a high PPT. Individuals with a low PPT at the wrist, which indicates more central sensitization, had two-times the odds of developing constant pain over 2 years, she added

Pre-existing sensitization drives pain

Similarly, in a poster presentation at the Osteoarthritis Research Society International World Congress, Neogi and her colleagues found that although factors such as depressive symptoms and pain catastrophizing were associated with developing knee pain, individuals with pre-existing sensitization had a higher risk of developing pain.

“We are starting to appreciate now that sensitization is not just coming on after [patients] develop osteoarthritis, but certainly, for some people, it is likely being influenced by developing osteoarthritis or pathology in the joint,” Neogi said.

She continued, “What this is showing is that even before [subjects] develop pain, [they] can have pre-existing sensitization and this can strongly drive development of pain. This understanding may provide a new avenue for pursuing a novel treatment target to lower the risk of developing chronic, persistent pain.”

The MOST longitudinal cohort study was conducted at centers in Boston, Birmingham, Ala., San Francisco and Iowa City, Iowa. – by Casey Tingle

References:

Carlesso LC, et al. Poster #602. Presented at: Osteoarthritis Research Society International World Congress. April 27-30, 2017; Las Vegas.

Neogi T, et al. Paper #30. Presented at: Osteoarthritis Research Society International World Congress. April 27-30, 2017; Las Vegas.

For more information:

Tuhina Neogi, MD, PhD, can be reached at Boston University School of Medicine, 72 East Concord St., Boston, MA 02118; email: tneogi@bu.edu.

Disclosure: Neogi reports no relevant financial disclosures. The study was funded by th