Knee Joint: The knee joint is one of the hardest and most crucial joints in the human body. It provides the lower leg to move relative to the thigh while holding the body’s weight. Activities at the knee joint are required for numerous everyday activities, including walking, running, sitting and standing.
The knee is a bicondylar type synovial joint, which principally allows for flexion and extension (and a little degree of medial and lateral rotation). It is composed by the articulations within the patella, femur, and tibia.
Articulating Surfaces of the Knee Joint
• Tibiofemoral – The medial and lateral condyles of the femur joining with the tibia.
• Patellofemoral – The anterior and distal part of the femur joining with the patella.
The tibiofemoral joint is the weight-bearing joints of the knee joint.
The patellofemoral joint provides the tendon of the quadriceps femoris (extensor of the knee) to be inserted directly over the knee, increasing the performance of the muscle. Both joint surfaces are padded with hyaline cartilage and enclosed inside a single joint cavity.
The patella is molded inside the tendon of the quadriceps femoris; its presence reduces wear and tear on the tendon.
Neurovasculature of the Knee Joint
The blood supply to the knee joint is by the genicular anastomoses throughout the knee, which is provided by the genicular branches of the femoral and popliteal arteries.
The nerve supply by the nerves which supply the muscles and which cross the joint. Those are the femoral, tibial and common fibular nerves.
Bursae of the Knee Joint
A bursa is a synovial fluid-filled sac, found within moving structures in a joint – with the aim of decreasing wear and tear on those structures. There are four bursae seen in the knee joint.
Prepatellar bursa – Found within the apex of the patella and the skin.
Suprapatellar bursa – This is an extension of the synovial cavity of the knee, located among the quadriceps femoris and the femur.
Semimembranosus bursa – Found posteriorly in the knee joint, within the semimembranosus muscle and the medial head of the gastrocnemius.
Infrapatellar bursa – Split into deep and superficial. The deep bursa lies among the tibia and the patella ligament. The superficial lies between the patella ligament and the skin.
Ligaments of the Knee Joint
The major ligaments of the knee joint are:
- Cruciate Ligaments – These two ligaments attach the femur and the tibia. In performing so, they crisscross each other, therefore the term ‘cruciate’ (Latin for like a cross)
• Anterior cruciate ligament – connects at the anterior intercondylar region of the tibia and ascends posteriorly to connect the femur, in the intercondylar fossa. It restricts anterior dislocation of the tibia onto the femur.
• Posterior cruciate ligament – connects at the posterior intercondylar region of the tibia, and ascends anteriorly to join to the femur in the intercondylar fossa. It restricts posterior dislocation of the tibia onto the femur. - Collateral ligaments – Those are two strap-like ligaments. They serve to stabilize the hinge motion of the knee, limiting any medial or lateral movement
• Tibial (medial) collateral ligament – A wide and flat ligament, located on the medial side of the joint. Proximally, it connects to the medial epicondyle of the femur, distally it joins to the medial surface of the tibia.
• Fibular (lateral) collateral ligament – Thinner and rounder than the tibial collateral, this connects proximally to the lateral epicondyle of the femur, distally it joins to a depression on the lateral surface of the fibular head. - Patellar ligament – An extension of the quadriceps femoris tendon distal to the patella. It joins to the tibial tuberosity.
Menisci of the Knee Joint
The medial and lateral menisci are fibrocartilage formations in the knee that serve two functions:
• To deepen the articular surface of the tibia, therefore increasing the stability of the joint.
• To perform as shock absorbers.
They are C formed and connected at both ends to the intercondylar area of the tibia.
In addition to the intercondylar attachment, the medial meniscus is attached to the tibial collateral ligament and the joint capsule. Any injury to the tibial collateral ligament results in tearing of the medial meniscus.
The lateral meniscus is shorter and does not have any extra attachments, rendering it fairly mobile.)
Movements of the Knee Joint
There are four principal movements at the knee joint:
Flexion: Provided by the hamstrings, gracilis, sartorius, and popliteus.Extension: Provided by the quadriceps femoris, which inserts into the tibial tuberosity.
Extension: Provided by the quadriceps femoris, which inserts into the tibial tuberosity.
Lateral rotation: Exhibited by the biceps femoris.
Medial rotation: Exhibited by five muscles; semimembranosus, semitendinosus, gracilis, sartorius and popliteus.
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