Surgical Anatomy. — In some of the lower animals the knee is composed of three distinct articulations. One between the outer tuberosity and the outer femoral condyle, another between the inner tibial tuberosity and the inner condyle of the femur and the third between the patella and the femur. In the human knee we have the analogues of these three joints although they are all merged into one. The crucial ligament attached to the inner condyle corresponds to the external lateral ligament of the inner articulation, and the crucial ligament attached to the outer condyle is analogous to the internal lateral ligament of the outer articulation. <Callout type="important" title="Important">The knee-joint is the largest and one of the most complicated in the body.</Callout> The posterior ligament limits extension of the knee, while the anterior ligament serves as the insertion of the quadriceps muscle. The semilunar cartilages, and their ligaments (the coronary and transverse) are described under the heading of 'Fracture and Dislocations of the Semilunar Cartilages', page 587. The bones entering into the formation of the knee-joint are long, and hence the leverage exerted against the ligaments of the joint is considerable. <Callout type="risk" title="Risk">Dislocations of the knee are extremely rare.</Callout> It is more common for unusual strain to produce fracture than to tear the ligaments. Fracture produced in this way most often consists in the avulsion of a small scale of bone corresponding to the insertion of the ligaments onto the tuberosity of the femur or tibia, in some instances, however, an entire condyle may be broken off by the pull of the ligament.<br><br>The most common dislocation occurring at the knee is so slight as to scarcely deserve the term of subluxation. It consists in a tearing of the internal lateral ligament so that the leg may be deviated outward and the inner condyle and tibial tuberosity may be separated a slight distance. Dislocations of the knee are classified according to the direction taken by the tibia. Accordingly there are anterior, posterior, internal and external luxations of the knee. In addition there is another type of dislocation in which the tibia is rotated on the femur.<br><br>The relation of the popliteal artery directly behind the articulation is of importance as already described under 'Fractures of the Lower End of the Femur'. The popliteal nerve situated somewhat more superficially in the popliteal space, and the peroneal nerve passing from behind the knee to the outer side of the leg where it winds around the head of the fibula, are sometimes injured in dislocations of the knee as evidenced by sensory and motor disturbances throughout their areas of distribution.<br><br>The most important motion in the knee-joint is that of the hinge type. In addition to this there is a slight gliding action between the femoral condyles and the tibia, and when the knee is flexed there is a slight rotary motion between the two bones. The hinge action takes place between the femoral condyles and the semilunar cartilages, while the gliding and rotary motion is between these cartilages and the tibia.<br><br>The antero-posterior luxations are more often incomplete than complete. Complete lateral luxations of the knee are extremely rare. The most common luxation is forward, and then in order of frequency, backward, outward, inward and rotary. Great violence is necessary to produce luxation of the knee. Probably the most common injury to the knee-joint consists in rupture of the internal lateral ligament with temporary separation of the articular surfaces on the inner side of the articulation.<br><br>Symptoms. — The accident is almost invariably the result of severe trauma and if the history of the case is elicited an idea of the degree of violence applied to the lower extremity at the time of the accident can usually be had. Pain, shock and loss of function are usually pronounced. Any of the luxations occurring at the knee may be complete or incomplete, simple or compound and complicated or uncomplicated by injury to vessels and nerves. The symptoms will vary according to the details of the case. Abnormal mobility is present. In complete luxations the action at the knee is usually flail-like and the percentage of cases in which the condition is compound is high.<br><br>In a complete forward dislocation of the knee treated by the author amputation was necessitated by the complete severance of the popliteal artery, and following the operation the knee-joint was partially dissected for the purpose of ascertaining the condition of the injured structures. The two lateral ligaments, the posterior ligament and the crucials were completely ruptured. The inner head of the gastrocnemius and the popliteus were torn across. The femoral condyles projected through a large rent in the popliteal space and their lower surfaces were about two and a half to three inches below the level of the tibial articular surfaces. The popliteal artery was completely torn across and the ends separated shortly above the popliteal notch. The popliteal and peroneal nerves were also completely divided. The semilunar cartilages remained with the tibia. This type of case is extreme and demands immediate amputation above the knee.<br><br>It is more common to see an incomplete dislocation in which a portion of the femoral condyles remains in contact with the tibial articular surfaces. The loss of alignment in the axes of the femur and tibia is apparent. The forward displacement of the tibia is seen at a glance. The patella is less prominent than normal because of the forward displacement of the tibia. If the artery is compressed or divided, loss of pulse and lowering of temperature below the knee will be noted. If the artery is simply compressed, but not otherwise injured, the pulse will return with reduction of the luxation. Pain may be intense if the nerves are stretched or compressed; if divided, sensory and motor paralyses will be present. In compound cases with laceration of the artery, hemorrhage is usually not profuse, strange as it may seem.<br><br>In backward luxations the relations of the tibia and femur at the knee, are reversed. The lower end of the femur is prominent anteriorly while the posterior edge of the upper end of the tibia may be palpated posteriorly. If the luxation is complete the bones override in a manner similar to that described in the anterior form of luxation. The condition is much more likely to be compound when the luxation is complete. The femur may penetrate the skin anteriorly or the upper end of the tibia may be found projecting through a rent in the popliteal space.<br><br>The lateral luxations usually consist of either inward or outward incomplete displacement of the tibia. Complete lateral luxation of the knee is quite rare and the complications accompanying the condition are usually less important than those occurring in the antero-posterior types.<br><br>In the rotary form of luxation, which is extremely uncommon, the tibia is seen to have rotated on its axis so that the normal relations between the articular surfaces are disturbed. The rotation is seldom more than forty-five degrees and is more often outward than inward. The axis of rotation may pass through the outer or inner tuberosity or in the region of the tibial spine. The ligamentous structures ruptured will depend largely on the axis of rotation.<br><br>In the different luxations occurring at the knee any or all of the ligaments binding the tibia to the fibula may be ruptured or one of their attachments avulsed, according to the nature and degree of the dislocation. Avulsion of the tibial spine has occurred in lieu of rupture of the crucials.<br><br>Traumatic reaction is usually pronounced during the first week or ten days following the accident. Function is completely lost in all forms of complete luxations of the knee. Active motion of the leg is sometimes only partially lost when the luxation is incomplete.<br><br>Treatment. — Traction in the long axis of the lower extremity with coaptation pressure on the displaced articular ends will usually suffice to reduce the luxation. A fragment of bone such as that <Callout type="gear" title="Gear">may be used for traction</Callout> and a splint or bandage may be applied to immobilize the joint. If the dislocation is complex, surgical intervention may be necessary.<br><br>The treatment of knee dislocations requires careful assessment and management to prevent complications such as nerve damage, vascular injury, and infection. Immediate medical attention should always be sought for suspected knee dislocations.
Key Takeaways
- The knee is the largest and most complex joint in the body, with multiple ligaments providing stability.
- Dislocations are rare but can be severe; they often involve rupture of ligaments or avulsion of bone fragments.
- Treatment involves reducing the dislocation through traction and immobilization, possibly followed by surgery.
Practical Tips
- Always seek medical attention for suspected knee dislocations to avoid complications such as nerve damage or vascular injury.
- Use a splint or bandage to immobilize the joint after reducing the dislocation.
- Be aware of signs of severe trauma like loss of pulse, temperature changes, and sensory/motor disturbances.
Warnings & Risks
- Dislocations can lead to serious complications such as nerve damage or vascular injury if not treated properly.
- Do not attempt to reduce a knee dislocation yourself; seek professional medical help immediately.
- Avoid applying excessive force during reduction attempts, which could worsen the injury.
Modern Application
While the techniques for treating knee dislocations have advanced significantly since 1915, understanding the anatomy and recognizing severe trauma remains crucial. Modern first responders can still benefit from this historical knowledge to quickly identify when professional medical care is needed.
Frequently Asked Questions
Q: What are the most common types of knee dislocations mentioned in the chapter?
The most common type of knee dislocation described is a subluxation, which involves tearing of the internal lateral ligament. Other types include anterior, posterior, internal, and external luxations, as well as rotary luxations.
Q: What are the symptoms of a complete forward dislocation of the knee?
A complete forward dislocation of the knee can result in the femoral condyles projecting through a large rent in the popliteal space, with their lower surfaces about two and a half to three inches below the level of the tibial articular surfaces. The popliteal artery may be completely torn across, leading to loss of pulse and temperature below the knee.
Q: What is the importance of the posterior ligament in the knee joint?
The posterior ligament limits extension of the knee but does not limit flexion since it has no attachment on the femur. It serves as the insertion for the quadriceps muscle, which helps keep the articular surfaces opposed.