THE LEX SOCIETATIS IN CHILEAN PRIVATE INTERNATIONAL LAW M aría i gnacia V ial u ndurraga 1*
III. EL RECONOCIMIENTO DE LAS SOCIEDADES EXTRANJERAS Y LA DETERMINACIÓN DE SU LEX SOCIETATIS EN EL DERECHO
Three joints make up the knee complex – the tibiofemoral, the superior tibiofibular, and the patellofemoral joints. Our principal concern is with the tibiofemoral and patellofemoral joints, but the superior tibiofibular joint will be addressed during PR-ROM.
Following are some anatomical observations that have clinical implications. Understanding the functional relationships (physiology) between structures and tissues (anatomy) will help explain how structures of the knee can be injured, and help us understand how orthopaedic tests work to provide the information that they do. Please review the anatomy of the joints and muscles involved in the function of the knee. And, it is suggested that the reader have an anatomy book at hand in order to more easily understand the information given below. The information that has been summarized here has been chosen because of its direct relevance to orthopaedic testing and understanding of mechanical pathologies of the knee.
Tibiofemoral Joint
The tibiofemoral joint is the largest joint in the body. Its synovium is extensive, communicating with many bursa and pouches around the knee. The two bones, the condyles of the femur and the tibial condyles (or plateau), are not congruent and, thus, have meniscal pads between them. There are several movements available to the tibiofemoral joint, depending on the position of the two bones, which are guided by ligaments and muscles. The more the knee is in extension, the less is rotation possible between the tibia and femur. In full extension, the collateral ligaments prevent lateral rotation and the cruciate ligaments prevent medial rotation. Hence, when weight-bearing and straight the knee is quite stable, relying on both muscle and ligaments for this stability. However, as the knee is flexed more and more it will lose some of its muscular and ligamentous support, and rotation of the tibia on the femur becomes available.
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Cruciate Ligaments
The anterior cruciate ligament (attached on the anterior portion of the tibia and the posterior portion of the femur) pulls and guides the femur forward during flexion of the knee, and prevents excessive posterior motion of the femur on the tibia. The posterior cruciate ligament (attached on the posterior tibia and anterior femur) pulls and guides the femur posteriorly during extension of the knee, and prevents excessive anterior movement of the femur on the tibia. Hence, the two work in tandem to move the femur forward and backward on the tibia during flexion and extension of the knee.
It is not so much that this guiding actually pulls the femur anteriorly or posteriorly, but rather that the ligaments hold the femur from moving anteriorly or posteriorly off the tibial plateau. This keeps the articulation of the knee joint occurring within only a small range of excursion on the tibia (i.e., keeping the meniscal pads from shifting too far anteriorly or posteriorly), while at the same time allowing the large and lengthy articulating surface of the femur to glide and move within the meniscal pad and on the surface of the tibial plateau. Therefore, the femur can roll while, for all intents and purposes, its contact on the tibia remains almost stationary.
Further, because the anterior attachments of both cruciates are slightly more medial than their posterior attachments, they will also tend to direct the femur to rotate medially very slightly on hyperextension of the knee (i.e., when the knee is locked when standing). Hyperextending the knee increases the tension on these ligaments as they begin to hook around each other where they cross.
This pulls the joint surfaces tightly together. The knee is unlocked by the popliteus muscle moving the femur in lateral rotation, back to neutral, so that flexion can occur. However, during lateral rotation of the tibia during flexion, the cruciates will move apart from each other and provide the laxity within the knee required for such rotation.
Collateral Ligaments
• The medial collateral ligament of the knee is also known as the tibiofemoral ligament, as it runs from the medial side of the medial epicondyle of the femur onto the medial side of the tibia. It is continuous with the fibrous joint capsule, and through that linked to the medial meniscus. Running up and down, the superior attachment is slightly posterior relative to the inferior attachment on the tibia. It becomes taut on knee extension and slack on knee flexion.
• The lateral collateral ligament of the knee runs from the lateral epicondyle to the head of the fibula.
Its superior attachment is slightly posterior to the inferior attachment on the head of the fibula.
As with the medial collateral it, too, is taut on extension of the knee and lax during flexion. Therefore, as flexion of the knee increases, the lateral-medial stability provided by these ligaments decreases.
Note: Lateral (external) rotation of the tibia is checked by both the lateral (fibular) and medial (tibial) ligaments. The cruciate ligaments resist medial/internal rotation of the tibia. One can remember which ligaments checks which tibial rotation by the phrase “lateral rotation stopped by collateral ligaments”
– hence, medial rotation is checked by the cruciate ligaments.
• Injuries to the collateral ligaments are more likely to happen when they are under strain, when the tibia is laterally/externally rotated (e.g., during valgus orientation of knee, which especially stresses the medial collateral). As valgus orientation of the knee occurs more often (even if it is only a momentary positioning) than a varus orientation, this is one reason that the medial collateral ligament is more often injured.
• Medial/internal motion of the tibia stresses the cruciates where they cross. Lateral/external rotation removes some tension off the ligaments. The ACL is usually injured when the leg is hit from the lateral side and the foot is planted on the ground (the classic occurrence is the football tackle).
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In such an injury, though the ensuing valgus orientation does produce lateral rotation of the tibia, nonetheless, the tibia is driven forward (but the foot cannot move), injuring the ACL while also stressing the medial collateral ligament. Because the medial collateral ligament is attached to the joint capsule, it will often tear the capsule (and its capillaries, etc.), which is how blood is able to enter the joint.
Further, the medial meniscus (see below) has attachments to the medial ligament and capsule, which hold it fixed, while the valgus movement of the knee has it pinched between the medial condyle of the femur and the tibia. Add the tibia moving anteriorly, and the meniscus will almost certainly be torn. Therefore, three tissues – the medial collateral ligament (and joint capsule), the medial meniscus and the ACL – can all be injured in the same trauma. This has been referred to as
“the terrible triad” since recovery from all three being injured at once can have a poor prognosis for anyone, especially professional athletes. Many a career has been ended by this triad, but surgery for any one of the three individually is often very successful.
• The posterior cruciate is often injured in soccer. If a running player’s foot strikes the ground rather than hitting the ball, the tibia is driven posteriorly, tearing the posterior cruciate. Or again, in football, a tackle from the front through the tibia will do the same. However, many people continue to function quite well without an intact PCL, as the muscular support often takes over its function.
Menisci Serve Several Functions:
• They act as shock absorbers, spreading the stresses over a larger area and protecting the condyles of the femur and tibia from wear;
• They aid in nutrition and lubrication of the joint by assisting in moving the synovial fluid within the joint capsule;
• They make the joint surfaces more congruent;
• They reduce friction during movement;
• They prevent pinching of the joint capsule (by not allowing the capsule to move between the tibia and the femur);
• They participate in the “screw home” mechanism by participating in guiding rotational motions in the knee.
The medial meniscus is crescent-shaped; the lateral meniscus is as well, but its ends almost meet.
The ends of the C-shapes are sometimes called the anterior and posterior horns of the meniscus.
At each of these ends or horns, the meniscal pad is thin. The pads are wedge-shaped (with a slightly concave surface that cups the condyle of the femur which it sits under), with the thickest portion of the medial meniscus at the medial side of the knee and the thickest portion at the lateral meniscus at the lateral side of the knee. The pads possess no nerves; pain felt is from the tearing of their supportive coronary ligaments. The two menisci are attached to each other by the transverse ligament of the knee.
The rounded shape of the articular surface of the femur fitting into the cup-shaped meniscal pad helps hold the menisci in place under the femoral condyles as the femur glides on the plateau of the tibia.
• During extension of the knee, the menisci are further assisted to move anteriorly, pulled partly by the fibres of the meniscopatellar ligament, and the lateral meniscus is further assisted by the meniscofemoral ligament fibres. As the femur rolls into extension, it pushes the patella anteriorly and superiorly, tightening the meniscopatellar ligament, which in turn pulls on the transverse ligament of the knee, pulling both menisci forward. Also, the posterior cruciate ligament tightens as the knee extends, pulling on the meniscofemoral ligament, which tugs the posterior horn of the lateral meniscus forward.
• During flexion of the knee, the medial meniscus has fibres from the semimembranosus tendon running to its posterior aspect, which help move the meniscus posteriorly, keeping it under the condyle. The popliteus has fibres to the posterior area of the lateral meniscus, and performs a similar function. The more firmly attached medial meniscus slides anteriorly and posteriorly during flexion only half as much (1/8 inch) as the more loosely attached lateral meniscus (1/4 inch).
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The medial meniscus is more often injured than the lateral. Some of the reasons for this are:
• The knee is more likely to undergo a valgus stress during injury (blows to the thigh and leg usually come from a lateral direction, severely compressing the meniscus);
• The medial meniscus is more securely fixed in place and, therefore, is more easily torn as it is unable to shift about under extreme pressure and at end-range motions of the knee;
• Combined with the fact that the medial meniscus has fibrous attachments both to the medial collateral ligament and the medial joint capsule, the following can occur: when tension is place on those structures, the medial meniscus can be pulled into positions that may cause the meniscus to be further pinched between the bones.
Patellofemoral Joint
The two principal purposes of the patella are: 1) to prevent friction between the quadriceps tendon and the femoral condyles; and 2) to act as an anatomic pulley that increases the efficiency of the quadriceps muscles. Both of these functions require the patella to move, and move along a track provided by the trough-like shape of the distal femur’s condyles.
• During flexion of the knee, the patella slides down (relative to the femur) into the intercondylar notch (onto the inferior surface of the condyles); while in extension, the patella will position itself between the (anterior surface) of the condyles.
• During rotation of the tibia on the femur, the patella will rotate; on medial rotation of the tibia (when the knee is flexed), the inferior apex of the patella rotates medially. On lateral rotation of the tibia, the apex rotates laterally.
Though the shape of a patella can differ between individuals, overall it usually is a basic oval shape:
broader at the superior portion and more pointed at the inferior end (the apex). The anterior surface is convex overall. The posterior surface is slightly V-shaped, which helps to keep the patella tracking between the condyles during the various movements between the femur and the tibia. There are several articular surfaces (facets) on the underside of the patella which, during proper tracking, articulate with the corresponding surfaces of the condyles.
If the orientation of the patella is altered by either too much tension (shortening) or too little tension (lengthening) of the quadriceps, then these patellar facets will not be aligned correctly and osteoarthritic changes will occur. This is commonly referred to a chondromalacia of the patella, a
“softening of the underside of the kneecap.” This results in a reflexive inhibition of the quadriceps muscles and the client will speak of the knee giving out occasionally.
It is estimated that during normal gait the patella is forced back upon the condyles by about two-thirds of one’s body weight. Going uphill or up stairs, this increases to two times one’s body weight, while going downhill or down stairs, this pressure increases to three-and-a-half times. Therefore, if the client, when asked when they feel that their knee will not hold them up replies, “it usually occurs coming down stairs,” we can assume that mild osteoarthritic changes (chondromalacia) are occurring. If they say that going up or down the stairs brings on their symptoms, then moderate damage has occurred.
Severe degenerative changes are occurring when walking on a flat surface brings on these symptoms.
The principal muscle, whose inhibition is seen as most crucial for the development of chondromalacia by improper tracking of the patella, is the vastus medialis, or even more specifically, a segment of that muscle referred to as the vastus medialis oblique (VMO). As the heads of the femur are wider apart than the knees during standing and walking, the bulk of the quadriceps muscles run down to the knee on an oblique angle. Therefore, there will be a pull to the lateral side of the knee. However, the patella has to run or track straight up and down (just as the femoral condyles are oriented). The vastus medialis (and VMO) is the only one of the four quadriceps muscles that is oriented in such a way as to pull the patella medially. Therefore, the patella is lifted by the muscles of the quadriceps pulling from both medial and lateral directions, which results in the patella lifting straight up.
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It is thought that the VMO needs to contract before the other three muscles in order for the patella to be able to track vertically. After all, the other three muscles are larger and outnumber the vastus medialis. If any injury or inhibition occurs that affects the VMO, then tracking problems begin and osteopathic changes result. To restore proper tracking, both the strength and the timing of the VMO need to be corrected.
The patella will dislocate, usually laterally, when it rises up and over one of the sides of the trough or valley created by the shape of the condyles. Possible reasons for this type of dislocation are a weakness in the VMO and/or a sudden contraction of the quadriceps while the tibia is externally/laterally rotated. The patella is driven right up and over the lateral condyle, and this is extremely painful.
The lateral condyle of the femur has a longer and steeper orientation that usually helps prevent this.
Superior Tibiofibular Joint
The junction between the superior tibia and fibula is a plane/gliding joint and is synovial. It has sometimes been found to be continuous with the popliteus bursa (and, hence, potentially with the synovium of the knee). It is re-inforced with anterior and superior ligaments that run from the head of the fibula in a superior and medial direction onto the tibia. It is further secured in place by the interosseus membrane running between the length of the shafts of the fibula and tibia.
The motion of the superior tibiofibular joint is linked to the movement of the ankle. As the foot is dorsiflexed, the fibula moves laterally away from the tibia at the ankle, and slides superiorly while it rotates internally. This occurs because:
1) the talus is wider at the front and as it moves up between the tibia and fibula, those bones are pushed slightly apart;
2) the inelastic fibres of the interosseous membrane between the tibia and fibula are on oblique angles, and as the two bones separate the fibres have to move more horizontal, and hence pull the fibula superiorly. (The fibula will move on the stable weight-bearing tibia);
3) as the fibres move horizontally, they must simultaneously pull their attachment on the anterior ridge of the fibula in a medial direction (internal rotation). Conversely, as the foot is plantar flexed, the fibula and tibia come closer at the ankle, the fibula will descend and rotate back out externally.
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Protocol
Case History (Specific Questions) Observations
Rule Outs
Active Free Range Of Motion (AF-ROM) Passive Relaxed Range Of Motion (PR-ROM) Active Resisted Range Of Motion (AR-ROM) Special Tests
Case History (Specific Questions)
1. Have you noticed any changes in function – an inability to perform daily activities? Sports?
2. Describe the nature of the pain. Note:
• Aching pain may indicate degenerative changes;
• Sharp, “catching” pain implies some mechanical problem;
• Pain at rest is often overuse – inflammatory in nature;
• Pain during activity is often structural or mechanical.
3. If swelling in the joint has occurred, you need to ask about the speed with which the joint swelled. If the joint began to swell immediately, it can mean that blood is a large component of the fluid present. If it took some time, several hours for example, for the swelling to slowly, gradually increase, then it is more likely due to just an increase in synovium. Nonetheless, ask the client if they have seen a physician. If you believe that blood is a possible component of the fluid, you need to refer the client out and have them seek immediate medical attention as they may need the knee aspirated (drained). (For the palpatory signs of blood in joint effusion, see Rule Outs: Joint Effusion).
Blood is corrosive to articular cartilage.
4. In the client’s own words, have them describe what is wrong with their knee.
Note if your client uses terms such as:
• Snapping – taut ligaments or tight tendons crossing the joint;
• Grinding (crepitus) – implies initial stages of osteoarthritic changes within the joint;
• Creaking (gross crepitus) – implies severe osteoarthritic degeneration;
• Catching or Locking – implies mechanical dysfunction of the ligaments and or meniscus;
• Giving way or becoming momentarily weak – implies patellar dysfunction.
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Specifically ask in this last case if the knee feels like it will give way when you go up stairs/uphill or when you go down stairs/downhill? Their answers will tell you: If it is felt going up/down hills or stairs it may mean retro patellar lesions. When someone walks up a set of stairs or uphill, the pressure exerted by the patella against the condyles of the femur is roughly 2.5 times their body weight, compared to .7 when walking on a level surface. When they go down stairs, the force is then 3.5 times their weight.
Hence, when osteoarthritis or chondromalacia begins in the retropatellar area it will usually first be
Hence, when osteoarthritis or chondromalacia begins in the retropatellar area it will usually first be