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U N I T 1 2
Musculoskeletal Function
and the anterior cruciate ligament (ACL) and posterior
cruciate ligament (PCL).
Ligamentous Injuries.
Ligamentous injuries of the knee
are among the most serious of all knee injuries. The mech-
anism is usually one of forceful stress against the knee
when the extremity is bearing weight. A “pop” or tear-
ing sensation along with sudden pain is often described,
especially with ACL ruptures. After injury, the ability to
bear weight on the extremity is often lost, and the knee
becomes swollen because of hemorrhaging into the joint.
Initial treatment includes rest, ice, and use of crutches
until the person is able to ambulate without a limp. A knee
immobilizer or range-of-motion brace may be used for
comfort until the acute pain subsides. Range-of-motion
exercises are important. Definitive treatment depends on
the ligaments that are involved, the person’s age and activ-
ity level, and any associated injuries. Most isolated lateral
ligament injuries and isolated ACL and PCL ruptures are
treated nonsurgically, at least initially. Surgical reconstruc-
tion may be required in young, active persons. Older and
less active individuals may be treated with physical ther-
apy aimed at controlling the instability. A well-constructed
brace may provide an option in some persons.
Meniscus Injuries.
The menisci are C-shaped plates of
fibrocartilage that are superimposed between the con-
dyles of the femur and tibia. There are two menisci in
each knee, a lateral and medial meniscus
5,8,12,13
(see Fig.
43-3). The menisci are thicker at their external mar-
gins and taper to thin, unattached edges at their inte-
rior margin. They are firmly attached at their ends to
the intercondylar area of the tibia and are supported
by the coronary and transverse ligaments of the knee.
The menisci play a major role in load bearing and shock
absorption. They also help to stabilize the knee by deep-
ening the tibial socket and maintaining the femur and
tibia in proper position. In addition, the meniscus assists
in joint lubrication and serves as a source of nutrition
for articular cartilage in the knee.
Meniscus injury commonly occurs as the result of
a rotational injury from a sudden or sharp pivot or a
direct blow to the knee, as in hockey, basketball, or foot-
ball. It is often associated with other injuries, such as a
torn ACL. The type and location of the meniscal tear
are determined by the magnitude and direction of the
force that acts on the knee and the position of the knee
at the time of injury. Meniscus tears can be described by
their appearance (e.g., parrot-beak, bucket handle) or
their location (e.g., posterior horn, anterior horn). The
injured knee is edematous and painful, especially with
hyperflexion and hyperextension. A loose fragment may
cause knee instability and locking.
Diagnosis is made by examination and confirmed by
MRI. A regular radiograph may be needed to rule out
osteoarthritis. Initial treatment of meniscal injuries may
be conservative. The knee may be placed in a removable
knee immobilizer. Isometric quadriceps exercises may be
prescribed. Activity usually is restricted until complete
motion is recovered. Arthroscopic meniscectomy may
be performed when there is recurrent or persistent lock-
ing, recurrent effusion, or disabling pain.
There is evidence that loss of meniscal function is
associated with progressive deterioration of knee func-
tion and osteoarthritic changes.
13
Damaged articular
cartilage has a limited capacity to heal because of its
avascular nature and inadequate mobilization of regen-
erative cells. Meniscal reconstruction procedures have
been developed to preserve these functions before sig-
nificant degenerative changes develop, thus preventing
the need for a total joint replacement later in life.
14
Patellar Subluxation and Dislocations.
Recurrent
subluxation and dislocation of the patella are common
in young adults.
5,8
Sports such as skiing or tennis involve
external rotation of the foot and leg with knee flexion,
a position that exerts rotational stresses on the knee.
Congenital knee variations are also a predisposing fac-
tor. There is often a sensation of the patella “popping
out” when the dislocation occurs. Other complaints
include the knee giving out, swelling, crepitus, stiff-
ness, and loss of range of motion. Treatment measures
include immobilization with the knee extended, brac-
ing, administration of anti-inflammatory agents, and
isometric quadriceps-strengthening exercises. Surgical
intervention often is necessary.
Patellofemoral Pain Syndrome.
Patellofemoral pain
syndrome is the most common cause of anterior knee
pain.
5,10,15
It is caused by imbalances in the forces con-
trolling movement of the patella during knee flexion and
extension, particularly with overloading of the joint.
The patellofemoral joint is composed of the patella
and the central groove in the proximal femur, which is
referred to as the patellar groove or femoral trochlea
(see Fig. 43-3). Stability of the joint involves dynamic and
Femur
Femoral condyles
Anterior cruciate ligament
Lateral
meniscus
Medial
meniscus
Tibia
Lateral
collateral
ligament
Femoral
trochlea
Patella
Meniscus tear
Patella
(removed for
clarity)
Lateral meniscus
Medial
meniscus
Front View
FIGURE 43-3.
The knee, showing the lateral and medial
condyles and menisci.The lateral and medial femotibial
condyles are located between the lateral and medial femoral
condyles and the tibial condyles (not shown). Inset (lower left)
shows meniscus tear.
