Abstract
ObjectiveThe objective was to investigate how postural control in knee osteoarthritis (KOA) patients, with different structural severities and pain levels, is reorganized under different sensory conditions.MethodsForty-two obese patients (BMI range from 30.1 to 48.7 kg*m−2, age range from 50 to 74 years) with KOA were evaluated. One minute of quiet standing was assessed on a force platform during 4 different sensory conditions, applied 3 times at random: Eyes open (EO) and eyes closed (EC) standing on firm and soft (foam) surfaces (EO-soft and EC-soft). Centre of pressure (Cop) standard deviation, speed, range and Cop mean position in both directions (anterior-posterior and medial-lateral) were extracted from the force platform data. Structural disease severity was assessed from semiflexed standing radiographs and graded by the Kellgren and Lawrence (KL) score. Pain intensity immediately before the measurements was assessed by numeric rating scale (range: 0–10).ResultsThe patients were divided into “less severe” (KL 1 and 2, n = 24) and “severe” (KL>2, n = 18) group. The CoP range in the medial-lateral direction was larger in the severe group when compared with the less severe group during EC-soft condition (P<0.01). Positive correlation between pain intensity and postural sway (range in medial-lateral direction) was found during EC condition, indicating that the higher the pain intensity, the less effective is the postural control applied to restore an equilibrium position while standing without visual information.ConclusionThe results support that: (i) the postural reorganization under manipulation of the different sensory information is worse in obese KOA patients with severe degeneration and/or high pain intensity when compared with less impaired patients, and (ii) higher pain intensity is related to worse body balance in obese KOA patients.
Highlights
Knee osteoarthritis (KOA) is a progressive joint disease associated with pain in and around the knees [1,2], impaired knee proprioception [3], balance impairments [4,5], and increased risk of falling [6]
It seems that the mechanisms behind the impaired posture control in knee osteoarthritis (KOA) involve on a complex interaction between the sensory information and the motor system controlling the body’s center of mass [16,17]
Obesity impairs balance in healthy subjects [25,26,27,28] and it is associated with the development [29,30] and progression [31] of KOA
Summary
Knee osteoarthritis (KOA) is a progressive joint disease associated with pain in and around the knees [1,2], impaired knee proprioception [3], balance impairments [4,5], and increased risk of falling [6]. Anaesthetizing the knee joint of KOA patients does not improve balance or knee proprioception, it increases the maximum quadriceps strength one hour after a bupivacaine injection [12] supporting the notion that pain inhibits muscle activation [13] and torque [14,15] It seems that the mechanisms behind the impaired posture control in KOA involve on a complex interaction between the sensory information and the motor system controlling the body’s center of mass [16,17]. Previous studies showed that ageing [22] and loss of a particular sense, as observed in patients with vestibular loss [19] and blind subjects [34], does not prevent reweighting of sensory information while controlling balance Clinically it is still an open question if obese KOA patients are capable of reorganizing their sensory input, and how this capability is affected by the disease severity and pain intensity. A better understanding of these mechanisms underlying the complex impaired behavior in obese KOA patients may benefit future rehabilitation protocols focusing on balance training to increase postural stability and reduce risk of falls
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