Most descriptions of the extensor mechanism of the knee do not take into account its complexity and variability. The quadriceps femoris insertion into the patella is said to be through a common tendon with a threelayered arrangement: rectus femoris (RF) most superficially, vastus medialis (VM) and lateralis (VL) in the intermediate layer, and vastus intermedius (VI) most deeply. We dissected 20 limbs from 17 cadavers to provide a more detailed description of the anterior components of the knee: the tendon, the patellar retinacula, and the patellofemoral ligaments. Only three of the 20 specimens exhibited the typically described quadriceps pattern. The remainder had bilaminar and even more complex trilaminar and tetralaminar fiber arrangements. We found an oblique head of the vastus lateralis (VLO), separated from the longitudinal head by a layer of fat or fascia, in 60% of the specimens. However, we found no distinct oblique head of the vastus medialis (VMO) in any specimen. The medial patellofemoral ligament (MPFL) was more common than the lateral (LPFL), supporting its suggested role as the principal passive medial stabilizer of the patella. Because the quadriceps muscle group plays a direct role in patellofemoral joint function, investigation into the clinical applications of its highly variable anatomy may be worthwhile with respect to joint dysfunction and failures of TKAs.

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BackgroundTo assess the relationship between rapidly destructive osteoarthritis (RDOA) of the hip and intra-articular steroid injections.MethodsCoding records from 2000 to 2013 were used to identify all subjects who had a fluoroscopy-guided intra-articular hip injection to treat pain associated with primary osteoarthritis. Radiographic measurements from preinjection and postinjection imaging were evaluated with Luquesne's classification of RDOA to determine diagnosis (greater than 50% joint space narrowing or greater than 2 mm of cartilage loss in 1 year with no other forms of destructive arthropathy). Demographic information, health characteristics, and number of injections were collected and analyzed as other potential explanatory variables. Patient outcome assessed by need for total hip arthroplasty (THA) after injection was also recorded.ResultsOne hundred twenty-nine injection events met the inclusion criteria in a total of 109 patients. From this sample, 23 cases of RDOA were confirmed representing a 21% incidence of RDOA. Twenty-one of the patients (91%) with RDOA had a THA at a median time of 10.2 months (interquartile range: 6.5-11.2) compared with 27 (31%) of those without RDOA at a median time of 24.9 months (interquartile range: 15.3-65.3). Older patients, patients with more severe osteoarthritis, and patients who identified themselves as white were more likely to have a diagnosis of RDOA (P = .008; P = .040; P = .009, respectively).ConclusionsThe potential for RDOA and faster progression to THA raises questions about the use of intra-articular steroid injections for hip osteoarthritis and should be discussed with patients. Additional studies are needed to define a true relationship.

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