Diurnal variation on balance control in patients with symptomatic knee osteoarthritis.
OBJECTIVE
Increasing evidence supports balance control impairment in older adult patients with knee osteoarthritis (OA). However, there is limited data on diurnal variation of balance control in these patients. This study aimed to investigate postural stability in older adult patients with symptomatic knee OA during different periods in a daytime.


METHODS
Two-hundred and forty-one patients with OA knee (median age=65 ± 12 years; 82 males) were enrolled in this study. Static posturography was performed under four standing conditions: eyes open and eyes closed, without and with foam support. To assess diurnal postural variations, testing sessions were defined as follows: 8-10 am, 10-12 am, 1 pm-3 pm, 3 pm-5 pm. Influence of sex, age, height, weight, and body mass index on postural stability was evaluated. Knee pain was also assessed in these four testing sessions.


RESULTS
Postural control was in particular less efficient in the late morning than in the early afternoon (p<0.05). Diurnal variation of balance control was more noticeable in older, heavier, and male patients (p<0.05). Patients' knee pain was more pronounced in the morning than in the afternoon (p<0.001).


CONCLUSION
Balance stability of patients with OA knee was different during a daytime. Altered postural performance in the morning could be explained by joint pain. This diurnal variation should be taken into account in the daily management of knee OA.