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120436143 knee joint anatomy

120436143 knee joint anatomy

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THE KNEE JOINT

The knee joint is a compound, condylar synovial joint, in which more than two

bones are involved in its formation. Three bones make up the knee joint, namely

(i) patella (ii) distal end of femur and (iii) proximal end of tibia. The fibula does

not contribute to the knee joint. The knee joint is the largest and most elaborate in

the body. It is primarily a hinge joint, allowing only flexion and extension. [It can

allow some degree of rotation when flexed, but not when fully extended].

Articular surfaces

These are formed by the femoral condyles, the patella and the tibial condyles. All

articular surfaces are covered by articular cartilage. The patella articulates only

with the femur. The femoral condyles articulate with the tibial condyles. However,

these surfaces are not congruent. Thus the presence of two menisci renders these

surfaces congruent.

Two major components can be recognized within the knee joint. These are:

(A) The femoropatellar joint

(B) The femorotibial joint

However, these two joints are continuous with each other.

(A) Femoropatellar joint

This is formed between the femoral trochlear and the patella. The latter is the

largest sesamoid bone in the body. The patella’s anterior surface is roughened for

the attachment of the quadriceps femoris tendon and patella ligament inferiorly.

The posterior surface is smooth, being covered by hyaline cartilage, and exhibits a

vertical midline ridge. The patella runs along the trochlear groove during flexion

and extension of the knee joint. Hence the patella acts as a pulley, increasing the

mechanical advantage of the quadriceps femoris muscle during extension of the

knee joint. The patella ligament is considered to be the tendon of insertion of the

quadriceps femoris muscle. This ligament attaches to the tibial tuberosity of the

tibia.

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(B) The femorotibial joint

This is constituted by the condyles of the femur and the condyles of the tibia.

Interposed between the condyles are two fibrocartilage discs, called the medial and

lateral menisci. Each meniscus is C-shaped, having a thick convex peripheral

border, and a thin concave central border. [The outer curved border of each

meniscus is attached to the joint capsule by the loose coronary ligament]. The

lateral meniscus is a more sharply curved “C” than the medial meniscus. The thin

tips of each meniscus are attached to the intercondylar area of the tibia. The

anterior convex margins of both menisci are attached to each other by a transverse

ligament. [In addition, the outer margin of the medial meniscus is firmly attached

to the deep surface of the tibial collateral ligament]. The menisci may contribute

to weight-bearing, but their main function is to increase congruity of the apposing

articular surfaces. [The inner concave margins and both the upper and lower

surfaces of the menisci project freely into the joint cavity]. A narrow posterior

meniscofemoral ligament connects the posterior convex surface of the lateral

meniscus to the medial femoral condyle. It runs just posterolateral to the posterior

cruciate ligament.

The Joint cavity and joint capsule

The joint capsule is attached along the articular margins of the femoral condyles

medially and laterally. It also attaches just above the intercondylar notch

posteriorly. Anteriorly, the joint cavity communicates with the suprapatellar

bursa. The latter lies between the distal end of the femur and the quadriceps

femoris muscle and tendon. The suprapatellar bursa is a good site for obtaining

synovial fluid samples or relieving severe swelling of the joint (say, when

inflamed). This archieved by inserting a needle along either the lateral or medial

margin of the patella.

Two other bursae may exist. These are the prepatellar and infrapatellar bursae.

The prepatellar bursa is subcutaneous, lying just anterior to the patella. When this

bursa is inflamed, there is pain and reduced mobility of the joint. The condition is

known as the “housemaid’s knee”. The infrapatellar bursa lies between the

patellar ligament and the proximal end of tibia. Both the prepatellar and

infrapatellar bursae do not communicate with the joint cavity. Also, distal to the

patella, the fibrous and synovial layers of the capsule are separated by the

intracapsular fat body.

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1 THE KNEE JOINT The knee joint is a compound, condylar synovial joint, in which more than two bones are involved in its formation. Three bones make up the knee joint, namely (i) patella (ii) distal end of femur and (iii) proximal end of tibia. The fibula does not contribute to the knee joint. The knee joint is the largest and most elaborate in the body. It is primarily a hinge joint, allowing only flexion and extension. [It can allow some degree of rotation when flexed, but not when fully extended]. Articular surfaces These are formed by the femoral condyles, the patella and the tibial condyles. All articular surfaces are covered by articular cartilage. The patella articulates only with the femur. The femoral condyles articulate with the tibial condyles. However, these surfaces are not congruent. Thus the presence of two menisci renders these surfaces congruent. Two major components can be recognized within the knee joint. These are: (A) The femoropatellar joint (B) The femorotibial joint However, these two joints are continuous with each other. (A) Femoropatellar joint This is formed between the femoral trochlear and the patella. The latter is the largest sesamoid bone in the body. The patella’s anterior surface is roughened for the attachment of the quadriceps femoris tendon and patella ligament inferiorly. The posterior surface is smooth, being covered by hyaline cartilage, and exhibits a vertical midline ridge. The patella runs along the trochlear groove during flexio ...
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