PHOTOGRAPHIC COMPARISON OF ARTICULATED JOINT MODELS REPRODUCING THE MOVEMENT OF THE KNEE

We wanted to assess the possible difference between the movement of the knee and the movement of the various brace joints normally used while dealing with knee traumas.
We based our remarks on the well known fact that the knee has a rotatory-translatory movement, as described by Smidt (1973), Fumagalli et al. (1977), Marinozzi and Pappalardo (1977), Kapandji (1977), Tittel (1979), Fleischmann and Line (1981), Nissel (1985), Insall (1986), Draganich et al. (1987), Yamaguchi and Zajac (1989), Melegatti (1997) and Steinbrück (1997).
The thigh is considered the starting point and the extended leg the 0° angle (Fig. 1). According to articular mechanics, during the first 25-30° flexion the knee has a pure rotatory movement (Fig. 2). From 25° on (Fig. 3, 4 and 5), the rotation is combined with a gliding (forward) movement of the femoral condyles on the tibial flat bone that becomes more and more progressive and prevailing.

We considered also opinions opposite to the above, e.g. Loudon et al (1998), Putz (1995), Townsend Ind. Inc., patent no. EP 0361405A, (04.04.1990), Townsend, Jeffrey H., Williams Robert J., US patent no. WO 9215264° (17.09.92). They are based on the hypothesis that during the flexion-extension the knee has a translatory-rotatory movement, i.e. the femur glides forward on the tibia for 8-9 mm (0-25°); the rotation phase follows from 25° on.

MATERIALS AND METHODS
In our research we reconstructed flat plastic models of the knee reproducing the outlines of femur and tibia with the average dimensions of adult bones. We chose four different kind of knee support joints and fixed them on the flat models.