Carol A. Courtney, PT, PhD

Study Design
Experimental laboratory study with repeated measures crossover design.

Background
Treatment effects of joint mobilization may occur in part by decreasing excitability of central nociceptive pathways. Impaired conditioned pain modulation (CPM) has been found experimentally in persons with knee and hip osteoarthritis (OA), indicating impaired inhibition of central nociceptive pathways. We hypothesized increased effectiveness of CPM following application of joint mobilization, determined via measures of deep tissue hyperalgesia.

Objectives
To examine the effect of joint mobilization on impaired CPM.

Methods
Examination of 40 individuals with moderate/severe knee OA identified 29 (73%) with impaired CPM. Subjects were randomized to receive 6 minutes of knee joint mobilization (intervention) or light manual cutaneous input only, one week apart. Deep tissue hyperalgesia was examined via pressure pain thresholds (PPT) bilaterally at knee medial joint line and the hand, at baseline, post-intervention and post-CPM testing. Further, vibration perception threshold (VPT) was measured at medial knee epicondyle at baseline and post-CPM testing.

Results
Joint mobilization, but not cutaneous input intervention, resulted in a global increase in PPT, indicated by diminished hyperalgesic responses to pressure stimulus. Further, CPM was significantly enhanced following joint mobilization. Diminished baseline VPT acuity was enhanced following joint mobilization at the knee that received intervention, but not the contralateral knee. Resting pain was also significantly lower following the joint intervention.

Conclusion
CPM was enhanced following joint mobilization, demonstrated by global decrease in deep tissue pressure sensitivity. Joint mobilization may act via enhancement of descending pain mechanisms, in patients with painful knee OA.

Level of Evidence
2B. J Orthop Sports Phys Ther, Epub 1 Jan 2016. doi:10.2519/jospt.2016.6259