Knee Joint
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- Is the largest and most complicated joint. Although structurally it resembles a hinge joint, it is a condylar type of synovial joint between two condyles of the femur and tibia. In addition, it includes a saddle joint between the femur and the patella.
- Is encompassed by a fibrous capsule that is rather thin, weak, and incomplete, but it is attached to the margins of the femoral and tibial condyles and to the patella and patellar ligament and surrounds the lateral and posterior aspects of the joint.
- Permits flexion, extension, and some gliding and rotation in the flexed position of the knee; full extension is accompanied by medial rotation of the femur on the tibia, pulling all ligaments taut.
- Is stabilized laterally by the biceps and gastrocnemius (lateral head) tendons, the iliotibial tract , and the fibular collateral ligaments.
- Is stabilized medially by the sartorius, gracilis, gastrocnemius (medial head), semitendinosus, and semimembranosus muscles and the tibial collateral ligament.
- Receives blood from the genicular branches (superior medial and lateral, inferior medial and lateral, and middle) of the popliteal artery, a descending branch of the lateral femoral circumflex artery, an articular branch of the descending genicular artery, and the anterior tibial recurrent artery.
- Is innervated by branches of the sciatic, femoral, and obturator nerves.
- Is supported by various ligaments and menisci.
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Knee Ligaments (Intracapsular)
| Knee
Intracapsular ligaments
1. Anterior cruciate ligament
- Lies inside the knee joint capsule but outside the synovial cavity of the joint.
- Arises from the anterior intercondylar area of the tibia and passes upward, backward, and laterally to insert into the medial surface of the lateral femoral condyle.
- Is slightly longer than the posterior cruciate ligament.
- Prevents forward sliding of the tibia on the femur (or posterior displacement of the femur on the tibia) and prevents hyperextension of the knee joint.
- Is taut during extension of the knee and is lax during flexion. (The small, more anterior band is taut during flexion.)
- May be torn when the knee is hyperextended.
2. Posterior cruciate ligament
- Lies outside the synovial cavity but within the fibrous joint capsule.
- Arises from the posterior intercondylar area of the tibia and passes upward, forward, and medially to insert into the lateral surface of the medial femoral condyle.
- Is shorter , straighter, and stronger than the anterior cruciate ligament.
- Prevents backward sliding of the tibia on the femur (or anterior displacement ofthe femur on the tibia) and limits hyperflexion of the knee.
- Is taut during flexion of the knee and is lax during extension. (The small posterior band is lax during flexion and taut during extension.)
3. Medial meniscus
- Lies outside the synovial cavity but within the joint capsule.
- Is C-shaped (i.e., forms a semicircle) and is attached to the medial collateral ligament and interarticular area of the tibia.
- Acts as a cushion or shock absorber and lubricates the articular surfaces by distributing synovial fluid in windshield-wiper fashion.
4. Lateral meniscus
- Lies outside the synovial cavity but within the joint capsule.
- Is nearly circular , acts as a cushion, and facilitates lubrication.
- Is separated laterally from the fibular (or lateral) collateral ligament by the tendon of the popliteal muscle and aids in forming a more stable base for the articulation of the femoral condyle.
5. Transverse ligament
- Binds the anterior horns (ends) of the lateral and medial semilunar cartilages (menisci).
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| Knee Ligaments (Extracapsular) | Knee
Extracapsular ligaments
1. Medial (tibial) collateral ligament
- Is a broad band that extends from the medial femoral epicondyle to the medial tibial condyle.
- Is firmly attached to the medial meniscus , and its attachment is of clinical significance because injury to the ligament results in concomitant damage to the medial meniscus.
- Prevents medial displacement of the two long bones and thus abduction of the leg at the knee.
- Becomes taut on extension and thus limits extension and abduction of the leg.
2. Lateral (fibular) collateral ligament
- Is a rounded cord that is separated from the lateral meniscus by the tendon of the popliteus muscle and also from the capsule of the joint.
- Extends between the lateral femoral epicondyle and the head of the fibula.
- Becomes taut on extension and limits extension and adduction of the leg.
3. Patellar ligament (tendon)
- Is a strong flattened fibrous band that is the continuation of the quadriceps femoris tendon. Its portion may be used for repair of the anterior cruciate ligament.
- Extends from the apex of the patella to the tuberosity of the tibia.
4. Arcuate popliteal ligament
- Arises from the head of the fibula, arches superiorly and medially over the tendon of the popliteus muscle on the back of the knee joint, and fuses with the articular capsule.
5. Oblique popliteal ligament
- Is an oblique expansion of the semimembranosus tendon and passes upward obliquely across the posterior surface of the knee joint from the medial condyle of the tibia.
- Resists hyperextension of the leg and lateral rotation during the final phase of extension.
6. Popliteus tendon
- Arises as a strong cord-like tendon from the lateral aspect of the lateral femoral condyle and runs between the lateral meniscus and the capsule of the knee joint deep to the fibular collateral ligament.
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Knee - Bursae
| Knee
Bursae
1. Suprapatellar bursa
- Lies deep to the quadriceps femoris muscle and is the major bursa communicating with
- the knee joint cavity (the semimembranosus bursa also may communicate with it).
2. Prepatellar bursa
- Lies over the superficial surface of the patella.
3. Infrapatellar bursa
- Consists of a subcutaneous infrapatellar bursa over the patellar ligament and a deep infrapatellar bursa deep to the patellar ligament.
4. Anserine bursa (known as the pes anserine)
- Lies between the tibial collateral ligament and the tendons of the sartorius, gracilis, and semitendinosus muscles.
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Tibiofibular Joints
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Proximal tibiofibular joint
- Is a plane-type synovial joint between the head of the fibula and the tibia that allows a little gliding movement.
Distal tibiofibular joint
- Is a fibrous joint between the tibia and the fibula.
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