Letter to the Editor on “Risk Factors, Outcomes, and Timing of Manipulation Under Anesthesia After Total Knee Arthroplasty”

To the Editor:
We read with great interest the study by Newman et al regarding risk factors and different timing of manipulation under anesthesia (MUA) in patients with stiffness after total knee arthroplasty (TKA) [1]. We would like to congratulate authors for such an interesting publication considering the appropriate design to answer the questions; however, there are some comments we would like to add in order to contribute to a better understanding of its clinical application.

First, we would like to highlight the methodology of this study which is consistent with the objective of determining the risk factors for early MUA after TKA. Although we consider it would have been useful to mention a measure of association such as odds ratio and its confidence interval, that could provide the magnitude of association of the variables of interest.

Secondly, authors conclude that an early intervention (before 6 weeks) significantly improves outcomes when compared to late MUA [1], [2], [3]. Despite the weaknesses acknowledged by authors, this conclusion is consistent with previous reports and the natural history of arthrofibrosis [4]. However, the most important limitation not only of this study but also in the whole scientific knowledge is the lack of criteria that defines the indication for an early intervention [5]. This limitation arises from the fact that the normal progression of range of motion after TKA has not been properly described.

In summary, the main purpose of this letter is to highlight that it is crucial to identify which of these patients require this early intervention, because range of motion thresholds for stiffness remain unclear [6]. Future research efforts in this field should be done.