The challenge of treating complex knee instability

It is important to recognize that the workup of revi-sion complex knee cases requires more than the physi-cal examination to help decipher the cause of the original failed reconstruction and to ultimately provide the best out-come for the patient. The patient’s alignment, sagittal plane slope, status of the menisci and articular cartilage surfaces and associated concurrent ligament injuries must all be assessed for every patient and for every case.Take for example the recently described “hidden menis-cus lesion” [7]. To quote Jack Hughston from almost 50 years ago, you may not have seen it in the past, but how many times has it seen you? In some cases, this lesion is not only a tear of the meniscus periphery but also deficiency of the entire posteromedial corner. If missed, high stresses will be exerted on the ACL graft during pivoting manoeu-vres, eventually leading to failure of ACL reconstruction. Similarly, meniscal root tears are often missed and the effects of missing these tears can affect the outcomes of associated ligament reconstructions and the development of osteoarthritis. Prospective studies have noted that these tears are often associated with ACL tears and other com-plex knee injuries [4]. Thus, it is our obligation to assess for these issues pre-operatively on MRI scans and to probe the meniscal root attachments and posteromedial and pos-terolateral meniscocapsular attachments in every case.While optimal surgical timing of repairs and reconstruc-tion is poorly defined, this special theme issue will also focus on knee anatomy and anatomical reconstructions. Repair of avulsed ligaments and tendons, whether soft tis-sue or bony avulsions, can successfully be performed in the acute phase; with the understanding that acute surgery for complex knee ligament injuries is associated with an increased risk of arthrofibrosis [6]. However, tendon avul-sions may be irreparable in the chronic setting necessitating allograft reconstruction with less desirable outcomes. There As clinicians it is humbling to accept the challenge of treat-ing patients with complex knee instability. Not only is our pre-operative evaluation sometimes limited and complex surgical techniques less standardized, there are also a mul-titude of surgical and post-surgical complications that are waiting for us and many revision operations to be done. In this special theme issue we chose a strategy of deconstruct-ing the topic of “complex knee instability” into multiple smaller, and easier to digest, subtopics: anteromedial, ante-rolateral, posteromedial and posterolateral corner ligament pathology and associated bony alignment and meniscal issues which are a necessary part of the workup of complex knee injuries. In the absence of Level I evidence for treat-ment of multiple ligament injuries, as clinicians we must be aware of knee instability patterns and their combinations, all while not forgetting the neurovasculature, whose evalua -tion and treatment comes first and often necessitates benign neglect of the multiple ligament injury.As we reflect on our own clinical practices, we often make the mistake of assuming that a case is an “isolated injury”, when in fact an isolated knee ligament injury is extremely rare, if not inexistent. Taking the anterior cruci-ate ligament (ACL) for example, when was the last time you treated an ACL tear without bone bruises, without MRI evidence of “oedema” or “high signal intensity” in the cap-sular structures and absolutely no injury to the articular cartilage or menisci? It depends on your point of view, but “looking for” concomitant injury sometimes affords addi-tional pre-operative workup, portals or approaches.