Hypoesthesia in Knee Osteoarthritis: Relationship of Pain, Vibration Perception and Proprioception

Purpose: Hypoesthesia, or partial loss of sensitivity to sensory stimuli has been reported in individuals with knee osteoarthritis (OA), with deficits reported in both proprioception (kinesthesia and repositioning) and vibration perception threshold (VPT) at the affected knee. The mechanisms underlying these deficits are unclear, however, previous evidence has indicated that diminished somatosensation, such as VPT may occur due to altered nociceptive processing. It has been postulated that similar mechanisms may explain deficits in kinesthesia, or the ability to detect passive joint movement in knee OA, however this premise has not been examined. It was hypothesized in this study that deficits in VPT and proprioception (kinesthesia) would be associated in subjects with knee OA. The purpose of this study was to explore the relationship between somatosensory measures of pain, vibration detection, proprioception and function in persons with knee OA. Methods: Fifteen individuals (mean age, 55.6±7.4y; 8 female; BMI 32.0±7) diagnosed with OA of the tibiofemoral joint by their physician (≥ grade II Kellgren and Lawrence radiographic changes) participated. Measurements included VPT at the knee using a biothesiometer, proprioception tested via threshold to detection of passive movement, resting and worst pain during the week prior to testing examined via Numeric Pain Rating Scale (NPRS), function using the Knee Outcome Survey Activities of Daily Living Scale (KOS) and isometric quadriceps strength. Results: Subjects reported resting pain (3.1±3.0) and worst pain (6.2±2.6) on the NPRS, and 56±16% on the KOS, indicating an average of 50% deficit in function. Quadriceps strength, vibration perception and proprioception were significantly different between limbs (p<0.05). These deficits were not correlated (r=.02) however a moderate correlation was found between proprioception deficits and resting and worst pain (r=.54, p<0.05), but not with vibration. No correlation was found between diminished function as measured by the KOS and both vibratory and proprioceptive deficits. Conclusions: Hypoesthesia, as measured by proprioception and vibration detection was significantly impaired on the painful OA limb compared to the contralateral limb and these findings were correlated to resting and worst pain. Functional deficits were only weakly correlated to somatosensory deficits, indicating that diminished function is likely multifactorial in nature.