The knee anatomy
comprises of the knee joint and its components- the bones, ligaments muscles blood supply and innervation. The knee connects the upper body to the legs, supports body weight and responsible for act of walking and running.
The knee joint
It is the largest human joint and a major part of knee anatomy; it is a compound joint with two cavities. It consists of two condylar joints between the femur bone (superiorly) and tibia (inferiorly) and a sellar joint between the patella (anteriorly) and femur. The former are partly divided by menisci between corresponding articular surfaces.
Articular surfaces: femoral condyles and tibial condyles.
- Menisci (Meniscus).
- Cruciate ligament.
- Transvers ligament
Meniscus: These are fibro-cartilages between the condyles of the femur and tibia; they increase congruency of the articulation. They are divided into lateral and medial. They have sharp free ends and other ends are attached to articular capsule.
They are united by the transverse ligament and divide the articular cavity into upper and lower part. They function to absorb shock and stress placed on the knee.
Cruciate ligaments: They are two: anterior and posterior cruciate ligament.
The articular capsule: The synovial membrane liens the inferior of the capsule and cruciate ligaments, forming synovial folds, villi and synovial bursae.
Synovial folds: The two alar folds that meet below the apex of the patella and infrapatellar synovial fold. The folds contain enough adipose tissue that forms infrapatellar fat pad.
Synovial bursae: These are the fluid sacs and synovial pockets that surround and sometimes communicate with the joint cavity.
There are eight synovial bursae in the knee joint;
Suprapatellar: Lies between femur and tendon of quadriceps femoris.
Popliteus: Between tendon of popliteus and lateral condyle of tibia.
Anserine: It separates tendons of Sartorius, gracilis and semitendinous from tibia and tibial collateral ligament.
Gastrocnemius: Lies deep to proximal attachment of tendon of medial head of gastrocnemius.
Semimembranosus: Located between medial head of gastrocnemius and semimembranous tendon.
Subcutanous prepatellar: Lies between skin and anterior surface of patella.
Subcutanous infrapatellar: Located between skin and tibial tuberosity.
Deep infrapatellar: Lies between patellar ligament and anterior surface of tibia.
Tibial collateral ligament: from medial epicondyle fuses with articular capsule and medial meniscus to tibia.
Fibular collateral ligament: from lateral epicondyle to head of fibula.
Oblique popliteal ligament: reinforces the capsule in the back, it goes backwards and lateral; towards the lateral condyles of the femur.
Arcuate popliteal ligament: from posterior surface of fibula, arches over the popliteus muscle to the edge of the capsule.
Patellar ligament: from patellar to the tibal tuberosity.
Medial and lateral patellar ligament: these are lateral and medial extensions of tendon of quadriceps femoris, which runs either sides of the patellar.
Movements of the knee joint: Extension, flexion, medial and lateral rotation.
Articular muscle of the knee: This lies deep to the vastus intermedius muscle and consists of fibers arising from the anterior surface of the femur proximally and attaching into the synovial capsule of the knee joint distally.
The articular muscle of the knee pulls the synovial capsule of the supraclavicular bursa superiorly during extension.
This is the fossa formed by the posterior part of the knee and is the only part of the knee anatomy
where a pulse can be felt, it consists of the following: the small saphenous vein runs between above muscles. Deep to this vein is medial sural cutaneous nerve, which followed proximally, leads to the tibial nerve. The tibial nerve is superficial to the popliteal vein which in turn is superficial to the popliteal artery.
Nerves of popliteal fossa: all motor braches from this region originate from the tibial nerve, one branch from its medial side the other from its lateral side.
The cutaneous branch of the tibial nerve joins a cutaneous branch of the common fibular (peroneal) nerve to form the sural nerve.
Popliteal artery: It lies on the floor of the popliteal fossa. The floor is formed by the femur, capsule of the knee joint and popliteal fascia.
The popliteal artery gives off genicular braches that also lie on the floor of the fossa and end by bifurcating into anterior and posterior tibial arteries at the proximal border of the soleus muscle.
Venous drainage of the knee
It consists of deep and superficial veins, deep veins run side by side with the corresponding deep arteries while the great saphenous vein is the major superficial vein.
Lymphatic drainage of knee
The popliteal lymphatic nodes lie deep to the fascia near the termination of the small saphenous vein. They receive afferents from;
- The territory of small saphenous vein.
- The deep pars of the leg.
- The knee.
Their efferents run along the popliteal and femoral vessels and terminate in the deep inguinal nodes.
Generally the knee anatomy is so complex that any damage to this part of the body may lead to serious disability most probably because the knee plays a great roll in movement of the body.