research instrumnet
Inspired by what was written by Insall (86) on the "Lack of significance of studies on the kinematics of the knee based on anatomical location of the instantaneous center of rotation" the knee motion was analyzed by a mathematical/experimental point of view in order to achieve a mechanical device that respects the physiological roto-translational movement.
Operationally, therefore, the purpose was to verify the variation of the distance between the center of rotation located on the femoral condyles to the various degrees of flexion (Kapandji 1977) and a point anthropometric (external malleolus) located on the leg itself. It should be noted that while the anthropometric point was perfectly traceable, the center of rotation had absolutely no chance to be traced visually or by touch.
For this purpose an instrument has been developed, similar to a leg extension, provided with a double-reading device, to be able to simultaneously carry out an angular reading (angular encoder) on the degree of flexion of the knee and a linear ( linear encoder) in order to determine the eventual "length variation" of the leg.
In particular, the machine has been designed with the possibility of making integral the thigh to the seat of the machine while the leg, was fixed through a clasp, free to move linearly along the movable arm of the leg extension, at the height of the malleolus which anthropometric reference. The movable arm at the height of the knee is activated by the extensor musculature of the lower limb, has been made free to rotate around its mechanical pivot (rotational motion) and at the same time allowed to the leg, through attaching the movable clasp to make a linear sliding towards the root of the limb itself (translational motion).
Both the measuring instruments were connected to a computer for simultaneous storage and processing of measurements taken.
The machine was then equipped with a movable seat driven by a motor connected to the computer capable of moving antero-posteriorly the session.
Particular care has been taken in the "support system" of the knee structured in two lateral semi- supports, inclined and converging downward, of which the lateral
one could transversely slide and approach to the medial.
Operationally, therefore, the purpose was to verify the variation of the distance between the center of rotation located on the femoral condyles to the various degrees of flexion (Kapandji 1977) and a point anthropometric (external malleolus) located on the leg itself. It should be noted that while the anthropometric point was perfectly traceable, the center of rotation had absolutely no chance to be traced visually or by touch.
For this purpose an instrument has been developed, similar to a leg extension, provided with a double-reading device, to be able to simultaneously carry out an angular reading (angular encoder) on the degree of flexion of the knee and a linear ( linear encoder) in order to determine the eventual "length variation" of the leg.
In particular, the machine has been designed with the possibility of making integral the thigh to the seat of the machine while the leg, was fixed through a clasp, free to move linearly along the movable arm of the leg extension, at the height of the malleolus which anthropometric reference. The movable arm at the height of the knee is activated by the extensor musculature of the lower limb, has been made free to rotate around its mechanical pivot (rotational motion) and at the same time allowed to the leg, through attaching the movable clasp to make a linear sliding towards the root of the limb itself (translational motion).
Both the measuring instruments were connected to a computer for simultaneous storage and processing of measurements taken.
The machine was then equipped with a movable seat driven by a motor connected to the computer capable of moving antero-posteriorly the session.
Particular care has been taken in the "support system" of the knee structured in two lateral semi- supports, inclined and converging downward, of which the lateral
one could transversely slide and approach to the medial.
This system has been structured in this way for a double reason:
the first to ensure that the contact between the popliteal area of the knee and the machine is carried out on "rigid" part of the femoral condyles and not on "soft" muscolar ones (which support of the rear part of the thigh on the seat of the machine), in order not to affect the linear measurement with the swelling of the musclolar ischio-crural mass due to the shortening of the rear compartment of the thigh during flexion;
the second to allow the possibility, approaching or moving away the two supports,to move vertically the horizontal intercondylar axis of the knee for greater precision in knee / machine alignment.
the first to ensure that the contact between the popliteal area of the knee and the machine is carried out on "rigid" part of the femoral condyles and not on "soft" muscolar ones (which support of the rear part of the thigh on the seat of the machine), in order not to affect the linear measurement with the swelling of the musclolar ischio-crural mass due to the shortening of the rear compartment of the thigh during flexion;
the second to allow the possibility, approaching or moving away the two supports,to move vertically the horizontal intercondylar axis of the knee for greater precision in knee / machine alignment.