Introduction. This study investigated the importance of the “oblique popliteal ligament” (OPL), and challenges its alleged ligament status. The currently named OPL is indigenous to the distal semimembranosus (SMT); therefore, by definition is not a ligament inserting from bone to bone. Clinically, a muscle-tendon unit is different then a ligament regarding proprioception and surgery. Methods. Literature search was conducted on texts, journals and websites regarding the formation of the OPL. Dissection of 70 knees included macro analysis, harvesting OPL, distal SMT and LCL samples and performing immunohistochemistry to 16 knees with antibody staining to the OPL, distal SMT and LCL. Results. All but one text claimed the OPL receives fibers from SMT. Macro dissection of 70 knees revealed the OPL forming from the distal SMT (100%). Microanalysis of OPL, distal SMT and LCL samples from 16 knees demonstrated expression of nervous tissue within selected samples. Discussion. No journals or texts have hypothesized that the OPL is a tendon. Clinically it is important we know the type of tissue for purposes of maximizing rehabilitation and surgical techniques. Conclusion. This study suggests the OPL be considered the oblique popliteal tendon as a result of the macro and micro evidence revealed. 1. Introduction The posterior aspect of the knee has been increasingly studied because of its clinical relevance. Surgeons, biomechanists, physical therapists, all health care providers dealing with the musculoskeletal system, and anatomists need to have a definitive and precise understanding of the structures of the posteromedial knee. A previous study conducted by the authors identified the clinical importance, morphology, and accurate terminology of the distal semimembranosus muscle tendon unit (SMTU) [1]. This study also revealed that the currently named oblique popliteal ligament (OPL) was indigenous to the SMTU and, therefore, by definition is not a ligament inserting from bone to bone. This is clinically important because of the proprioception of a tendon versus a ligament, which may suggest a greater role by the distal semimembranosus tendon in posterior knee stability. With regard to the literature regarding the oblique popliteal ligament, Woodburne’s Essentials of Human Anatomy states that it is formed from the fibers of the distal semimembranosus tendon [2]. All other anatomical texts and atlases that consider or depict the OPL state that the distal semimembranosus tendon contributes fibers to the OPL [2–20]. Though the majority of the texts and journal papers
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