Patella

Patella structure

The patella is the largest sesamoid of a skeleton of the person. It is located in the thickness of a kvadritsepsabedr, is well palpated through skin, easily displaced at the unbent knee. The upper edge of a patella has rounded shape, is called the patella basis. The patella top (its bottom edge) has slightly extended form. The front surface of this bone is rough, in it there are openings for blood vessels, and also the place of an attachment of a sinew of a direct muscle of a hip is located. On the back (joint) surface of a patella allocate two unequal parts limited to vertically located comb: smaller – a medial part, big – lateral. These areas are covered with a joint cartilage. The lateral joint surface is jointed with an outside condyle of a hip, medial – with an entocondyle. Some more medialny the area at full extension of a knee adjoining to a femur entocondyle is located. The thick layer of a joint cartilage considerably improves congruence of the adjoining surfaces, and also reduces compression loads of a knee joint. At newborns the patella has cartilaginous structure. The center of ossification of a patella appears approximately in 2-4 years.

The patella is a rotation center. It provides overall performance with the four-head of a muscle of a hip by transfer of load of area of a knee joint. Load of a patella is distributed very difficult and consists both in stretching, and in compression with the minimum friction. The structure of this bone reflects a ratio of forces which are constantly influencing it.

Patella ligament

The ligament of a patella originates from a patella top, is attached to tuberosity of a tibial bone. It provides distribution of the stretching loadings influencing a knee joint. Fibers of this sheaf begin enough far apart in the field of the back and lower surface of a patella. Near the place of an attachment also a tenofibris of a direct muscle of a hip joins them. 85% of dry matter of a ligament of patella are made by collagen.

Patella shift

The patella ties muscles of a shin and the front surface of a hip. Normal it densely keeps on the place. At disturbances of a structure of a patellar surface (flattening, a roughness) this bone can slide off it, at the same time there is a patella shift: incomplete dislocation or dislocation.

Patella dislocation

Dislocation of a patella is option of its instability. Dislocation of a patella can be caused by many factors, but at a pathogeny there is always stretching of the outside sheaf supporting a patella and also an atrophy of muscles and an abnormal shape of legs (A x-shaped curvature, overextension). The main signs of such shift of a patella are pain and feeling of instability in the field of a knee joint in front, in the anamnesis the injury (damage of a knee joint) or an operative measure on a knee joint with mobilization of the outer edge of a patella takes place. On the roentgenogram at this pathology characteristic symptoms of dislocation of a patella are found. Treatment more often conservative, consisting in stabilization of a patella. Orthoses or bandages are for this purpose used. At preservation of symptoms which break function of an extremity an operative measure is necessary.

Patella fracture

The fracture of a patella is quite frequent injury. It arises usually when falling on the bent knee. Less often the fracture of a patella occurs at direct stroke to this bone, is extremely rare – at strong draft of a sinew. Symptoms of such injury are the pain amplifying at the movement by the lower extremity, hypostasis, impossibility to unbend, and also to raise the straightened leg, deformation. Treatment of a fracture of patella depends on the nature of the fracture, and also existence of shift of fragments. Conservative treatment is possible at stable changes without shift. In other cases an operative measure is required.