Background/Purpose

Knee osteoarthritis (OA) pain is neither constant nor stable and exacerbations of pain are disabling. We examined whether knee injury and buckling (giving way) are triggers for exacerbation of pain, also defined as flare, in persons with symptomatic knee OA. 

Methods

We conducted a web-based case-crossover study with all data collected via the Internet. Participants with painful radiographic knee OA were recruited and followed at 10-day intervals for 3 months (control periods). Participants were instructed to additionally record knee pain exacerbations during the 3 months interval.  Pain exacerbation was defined as an increase of 20mm from baseline on VAS knee pain score (VAS 0-100). Information about triggers occurring during “control periods” (without pain exacerbation) and “hazard periods” (immediately preceding the pain exacerbation) was collected. We collected data on potential triggers by asking for acute knee injuries in the previous seven days. Similarly we asked about knee buckling events, defined as giving way in the previous two days (i.e., date of pain exacerbation for hazard period, and date of data assessment for control periods). The relationship of knee injury and buckling to the risk of pain exacerbation was examined using conditional logistic regression models.

Results

Of the 297 participants (women: 61%, mean age: 62 years, mean BMI: 29.3 kg/m²) recruited, 157 (53%) had both hazard and control periods and were included in the data analysis.  Sustaining a knee injury increased the likelihood of experiencing a pain flare (odds ratio (OR) 10.2; 95% CI 5.4, 19.3) compared to no injury (Table).  An event of knee buckling increased the likelihood of experiencing a pain exacerbation (OR 4.0; 95% CI 2.6, 6.2) compared to no buckling and the risk increased with a greater number of buckling events (for ≥ 6 buckling events, OR 20.1; 95%CI 3.7, 110).

Table

 Association of knee injury and risk of knee pain exacerbation

Association of knee buckling and risk of knee pain exacerbation

Conclusion

Knee injury and buckling are associated with knee pain exacerbation.  Reducing the likelihood of knee injury and buckling through avoidance of particular activities and/or appropriate rehabilitation programs may decrease the risk of pain exacerbation.