Acute dislocation of knee-joint is a serious injury. The condition is rare in comparison with dislocations of other joints.
MECHANISM OF INJURY
Severe violence is required to produce the lesion. This is more common following an automobile accident.
NATURE OF LESION
The lesion can be of varying severity. The dislocation may be posterior, anterior, medial, lateral or of rotatory type. There is associated rupture of the capsule, medial, lateral and cruciate ligaments. The popliteal artery may be severely damaged producing gangrene of the affected leg and foot. Traction lesion may affect both the divisions of the static nerve. Peroneal nerve lesion is more commonly present. The patella may be fractured, and associated disruption of the extensor apparatus may co-exist.
Clinical examination: The diagnosis of dislocation becomes apparent by clinical examination. The nature of deformity gives the idea of the type of lesion produced. Blood supply of the lower limb is tested by observing the color, temperature, and arterial pulsation. Sensory and motor functions of both the divisions of the sciatic nerve are tested.
X-ray: X-ray shows the nature of displacement. There may be an associated fracture of the tibial spine or styloid process of the fibula.
The immediate emergency measure is undertaken to save the limb. The procedure may be a lengthy one where exploration of the popliteal artery and peroneal nerve is required.
- Reduction of dislocation: Under general anaesthesia closed reduction is attempted. In most cases this procedure is successful. Two assistants apply traction by holding the leg and thigh. The displacement is then corrected by the orthopedic surgeon holding the upper end of the femur by the other.
- Aspiration: The blood from the knee-joint is aspirated.
- Dorsal splint: A dorsal plaster slab is then applied with the knee flexed at 160⁰ position.
- Limb in elevation: While in bed, the leg is kept elevated on a pillow. The circulatory efficiency is observed carefully by checking the condition of the limb at intervals.
- Application of plaster cylinder: Once the swelling of the knee has settled, the dorsal plaster slab is replaced by plaster cast extending from the groin to foot. Immobilization is maintained for a period of 10-12 weeks.
Exercise: Quadriceps exercises are started from the beginning. The patient can walk around once he can lift the leg up.
Operative treatment: Operation may be required in cases of failure to reduce the dislocation by the conservative method. This may be due to the capsule or other soft tissues being interposed between the ends of the bones. Popliteal vessel and nerve may require exploration when their functions are threatened. Reconstruction of the ligaments can be done as an immediate procedure during the time of operative reduction using different orthopedic implants. The procedure can be delayed when closed reduction has been performed.
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