Reply to Chmielewski and Snyder-Mackler.

REPLY: In the letter of Chmielewski and Snyder-Mackler, the authors pointed out that the clinical classification scheme used in their studies is not comparable to ours to separate anterior cruciate ligament (ACL) patients without “giving-way symptoms” (copers) from ACL patients with giving-way symptoms (noncopers). In contrast to their comprehensive screening protocol that included issues of different movement tasks, we were exclusively focused on the patients statement if there was any episode of giving-way symptoms or not. This was evaluated with a questionnaire consisting of four different specific questions with regard to dynamic knee stability in daily life. The occurrence of one single giving-way episode was sufficient to classify our ACL patients as noncopers, whereas (Chmielewski et al. 2005) conceded one episode based on their screening protocol. In this special case, it may be argued that our classification regarding copers or noncopers was stricter than the screening protocol reported by Chmielewski and SnyderMackler. In detail, their screening protocol contains highdemand movement tasks that are associated with high loads acting on the knee joint. The occurrence of one episode was accepted to still classify this patient as coper. On the other hand, an evaluation of daily activities was performed (as well as we did it in our study), and also in this case, one episode was accepted to differentiate patients to copers, whereas in our protocol, these patients were signed as noncopers. In fact, Chmielewski and Snyder-Mackler annotated that the trauma of ACL failure in the patients of our study was 1 yr from injury; this displays a clear difference from the classification scheme of Chmielewski and Snyder-Mackler. We agree with their notion, but one has to consider that in our hospital, patients with ACL rupture will mostly undergo surgical treatment after 2–4 mo. In summary, it was not our intention to directly compare the clinical classification scheme of Chmielewski and SnyderMackler with our screening protocol. Moreover, we did not intend to challenge their scheme. To avoid misunderstanding for the readers, we would like to state that the classification scheme used in our study is clearly different from that of Chmielewski and Snyder-Mackler.