The first thing is that when we are weight-bearing we define the kinetic chain as being a closed chain anchored by the floor or the surface upon which the foot is resting. In the closed kinetic chain the relationship of the foot to the ground is of paramount importance to the knee. This photo shows calcaneal or rear-foot valgus – sometimes called eversion – and the common accompanying condition of excessive pronation or pes planus. Valgus refers to the relationship of the calcaneus to the tibia. We will be referring to this relationship frequently in this presentation. I wanted you to see clearly what we were talking about. This slide and the next illustrate common patterns of lower extremity alignment and we present them here to reinforce the fact that the knee is acted upon, and may compensate for, conditions both up and down the kinetic chain. Genu valgum, for whatever the cause, is usually associated with a lateral position of the patella, hip adduction, excessive pronation at the foot and an increased Q angle. All of these are implicated consistently in knee pain and are amenable to change.
The second common pattern is genu varus, also accompanied in this case by medial tibial rotation, hip abduction and compensatory pronation at the foot. I’m sure we are all used to seeing both of these painful conditions resting in the middle of both of these arrangements.
Now to look at the knee itself. This illustration depicts the expected path of the patella during knee motion. It moves vertically between flexion and extension and we expect it to move in a smooth, sinusoidal path. We will be addressing patellar tracking in the upcoming vignettes, however it is important that we all recognize that cases and cases of diagnosed patellofemoral pain, patellar abnormalities actually appear in only about half of the cases, so it’s not a universal problem. Of course, the quadriceps. Books are written on the quadriceps. We only have one picture. A central focus in any knee discussion is the quadriceps and the forces formed by its muscular components. It’s important for its crucial role in knee extension and sometime forgotten in its importance as a shock absorber during weight-bearing activities. However, it is also important for its role as a dynamic stabilizer of the patella but virtue of its various force vectors. Although there is controversy still – and probably always will be – regarding the details of the vastus medialis obliquus and vastus lateralis activation timing and strength. It’s fairly well agreed now that something going on here does contribute in many instances to understanding and treating patellofemoral pain.
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