Bias in the Methodology: Sleep Quality Is Related to Worsening Knee Pain in Those With Widespread Pain.

We read with great interest the article in The Journal entitled, "Sleep Quality Is Related to Worsening Knee Pain in Those with Widespread Pain: The Multicenter Osteoarthritis Study" by Dai, et al 1 The authors reported the association between sleep quality and odds of developing knee pain, and how widespread pain modified this relationship.