Lateral Gastrocnemius Tendon. The lateral gastrocnemius tendon originates at or near the supracondylar process of the distal femur. In this region, this tendon can be easily identified by blunt dissection medial and distal to the long head of the biceps femoris in the interval between the lateral gastrocnemius and the soleus muscle. On average, it attaches 13.8mm posterior to the FCL, 28.4mm posterior to the popliteus tendon insertion, and is nearly inseparable from the meniscofemoral portion of the posterior capsule. At the level of the fibular styloid, the lateral head of the gastrocnemius blends with the popliteofibular ligament, providing varying degrees of additional posterolateral stability.9
JOINT CAPSULE/MIDTHIRD LATERAL CAPSULAR LIGAMENT
The joint capsule can be divided into superficial and deep laminae. The 2 laminae become confluent anterior to the overlying iliotibial band. The inferior lateral geniculate artery, traveling through an anterior truncated space between the deep and superficial laminae, always separates these 2 capsular structures.10
The superficial lamina, which is the original capsule embryologically, encompasses the FCL and ends posteriorly at the fabellofibular ligament. The deep capsular lamina is phylogenetically younger and is a result of the fibula receding from the lateral femur. It extends posterolaterally and forms the coronary ligament and the hiatus for the popliteus tendon.
JOINT CAPSULE/MIDTHIRD LATERAL CAPSULAR LIGAMENT
The joint capsule can be divided into superficial and deep laminae. The 2 laminae become confluent anterior to the overlying iliotibial band. The inferior lateral geniculate artery, traveling through an anterior truncated space between the deep and superficial laminae, always separates these 2 capsular structures.10
The superficial lamina, which is the original capsule embryologically, encompasses the FCL and ends posteriorly at the fabellofibular ligament. The deep capsular lamina is phylogenetically younger and is a result of the fibula receding from the lateral femur. It extends posterolaterally and forms the coronary ligament and the hiatus for the popliteus tendon.
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| FIGURE 7. Attachment sites of the anterior (AD) and posterior (PD) (over surgical pickups) divisions of the popliteofibular ligament (PFL) at the popliteus musculotendinous junction (medially) and the medial aspect of the fibular head and the fibular styloid process (laterally) (posterior view of the right knee). FCL, fibular collateral ligament; PLT, popliteus tendon. Reprinted with permission.23 |
The deep lamina travels along the lateral meniscus and spans from the junction of the popliteus muscle and tendon to its termination at the popliteofibular ligament. In the cranial to caudal direction, it extends from the femur to the fibula. An in vivo anatomic and magnetic resonance imaging study demonstrated that the most inferior extent of the capsular reflection of the knee is along the posterior fibula. The most extensive capsular reflection was less than 14mm inferior to the subchondral bone of the proximal tibia. This anatomic finding has lent credence to the recommendation of placing fine wires for circular fixators no closer than 15mm inferior to the articular surface to minimize the incidence of iatrogenic knee sepsis secondary to pin tract infection.19
The joint capsule of the knee can be divided into 3 sections in the anterior to posterior direction: anterior, lateral, and posterior. The anterior section extends from the patella tendon to the anterior border of the popliteus tendon’s insertion on the femur. It is adherent to the patellar fat pad, intermeniscal ligament, and anterior horn of the lateral meniscus. The lateral capsule extends from the anterior border of the popliteus tendon’s insertion on the femur to the lateral gastrocnemius attachment. The posterior capsule is attached to the femur, proximal to the articular margin of the lateral femoral condyle.7,10,20
From medial to lateral, the posterior capsule is covered by the muscular origins of the plantaris and lateral gastrocnemius muscle and tendon. Distally, it blends with the musculotendinous junction of the popliteus and the posterior division of the popliteofibularligament. The midthird lateral capsular ligament is a thickening of the lateral capsule of the knee. It is divided into 2 components: the meniscofemoral and meniscotibial components. It is thought to be homologous to the deep medial collateral ligament on the medial aspect of the knee. The meniscofemoral component extends from the femur down to the meniscus and the mensicotibial component extends up from the tibia to the meniscus.
Anterior to the popliteal hiatus, the lateral meniscus is stabilized by the meniscotibial portion of the midthird lateral ligament. Biomechanically, this structure is thought to be an important secondary stabilizer to varus instability.4,5
CORONARY LIGAMENT OF THE LATERAL MENISCUS
The coronary ligament of the lateral meniscus lies posterior to the midthird lateral capsular ligament. It is the meniscotibial portion of the posterior joint capsule extending from the anterior margin of the popliteal hiatus to the lateral aspect of the posterioinferior popliteomeniscal fascicle. It secures the posterior horn of the lateral meniscus to the tibia. The coronary ligament is important clinically in providing resistance to hyperextension and posterolateral rotation of the tibia.5
OBLIQUE POPLITEAL LIGAMENT
The oblique popliteal ligament (or ligament of Winslow) is formed by the coalescence of the oblique popliteal expansion of the semimembranosus and the capsular arm of the posterior oblique ligament. These 2 structures originate from the medial side of the knee, merge anterior to the medial head of the gastrocnemius, and form the oblique popliteal ligament. This ligament crosses the midsagittal plane of the knee at the level of the tibial insertion of the PCL and attaches to the inferomedial edge of the fabella and the lateral capsule.5,10,20,21
FABELLOFIBULAR LIGAMENT
The fabellofibular ligament is the most distal edge of the capsular arm of the short head of the biceps femoris.4 It spans from the lateral edge of the fabella, distally and laterally, to attach to the fibular head just posterior to the attachment of the posterior division of the popliteofibular ligament. If no osseous fabella is present, the ligament’s fibers blend with the anterior fibers of the lateral gastrocnemius tendon, on the posterior aspect of the supracondylar process of the femur, becoming part of the superficial capsular layer. In a cadaveric study, LaPrade et al4 found an ossified fabella in 5 of 30 (20%) specimens. In the absence of a bony fabella, some authors have named the structure the short lateral ligament.10,20 The fabellofibular ligament is in the greatest tension when the knee is in full extension and is often difficult to identify as it relaxes with knee flexion.5,21 Therefore, the clinical significance seems to be important for providing stability of the knee close to full extension. However, biomechanical studies specifically on the fabellofibular ligament have not been performed.
The joint capsule of the knee can be divided into 3 sections in the anterior to posterior direction: anterior, lateral, and posterior. The anterior section extends from the patella tendon to the anterior border of the popliteus tendon’s insertion on the femur. It is adherent to the patellar fat pad, intermeniscal ligament, and anterior horn of the lateral meniscus. The lateral capsule extends from the anterior border of the popliteus tendon’s insertion on the femur to the lateral gastrocnemius attachment. The posterior capsule is attached to the femur, proximal to the articular margin of the lateral femoral condyle.7,10,20
From medial to lateral, the posterior capsule is covered by the muscular origins of the plantaris and lateral gastrocnemius muscle and tendon. Distally, it blends with the musculotendinous junction of the popliteus and the posterior division of the popliteofibularligament. The midthird lateral capsular ligament is a thickening of the lateral capsule of the knee. It is divided into 2 components: the meniscofemoral and meniscotibial components. It is thought to be homologous to the deep medial collateral ligament on the medial aspect of the knee. The meniscofemoral component extends from the femur down to the meniscus and the mensicotibial component extends up from the tibia to the meniscus.
Anterior to the popliteal hiatus, the lateral meniscus is stabilized by the meniscotibial portion of the midthird lateral ligament. Biomechanically, this structure is thought to be an important secondary stabilizer to varus instability.4,5
CORONARY LIGAMENT OF THE LATERAL MENISCUS
The coronary ligament of the lateral meniscus lies posterior to the midthird lateral capsular ligament. It is the meniscotibial portion of the posterior joint capsule extending from the anterior margin of the popliteal hiatus to the lateral aspect of the posterioinferior popliteomeniscal fascicle. It secures the posterior horn of the lateral meniscus to the tibia. The coronary ligament is important clinically in providing resistance to hyperextension and posterolateral rotation of the tibia.5
OBLIQUE POPLITEAL LIGAMENT
The oblique popliteal ligament (or ligament of Winslow) is formed by the coalescence of the oblique popliteal expansion of the semimembranosus and the capsular arm of the posterior oblique ligament. These 2 structures originate from the medial side of the knee, merge anterior to the medial head of the gastrocnemius, and form the oblique popliteal ligament. This ligament crosses the midsagittal plane of the knee at the level of the tibial insertion of the PCL and attaches to the inferomedial edge of the fabella and the lateral capsule.5,10,20,21
FABELLOFIBULAR LIGAMENT
The fabellofibular ligament is the most distal edge of the capsular arm of the short head of the biceps femoris.4 It spans from the lateral edge of the fabella, distally and laterally, to attach to the fibular head just posterior to the attachment of the posterior division of the popliteofibular ligament. If no osseous fabella is present, the ligament’s fibers blend with the anterior fibers of the lateral gastrocnemius tendon, on the posterior aspect of the supracondylar process of the femur, becoming part of the superficial capsular layer. In a cadaveric study, LaPrade et al4 found an ossified fabella in 5 of 30 (20%) specimens. In the absence of a bony fabella, some authors have named the structure the short lateral ligament.10,20 The fabellofibular ligament is in the greatest tension when the knee is in full extension and is often difficult to identify as it relaxes with knee flexion.5,21 Therefore, the clinical significance seems to be important for providing stability of the knee close to full extension. However, biomechanical studies specifically on the fabellofibular ligament have not been performed.
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