Webster's New World Medical Dictionary

knuckle
Klippel-Feil syndrome
A congenital disorder
involving the fusion of any two of the 7 neck (cervi-
cal) vertebrae. Affected individuals have a short
neck, low hairline at the nape of the neck, and lim-
ited movement of the head. Klippel-Feil syndrome is
due to a defect in the early development of the
spinal column in the neck and may be assocaited
with other birth defects. Also known as Klippel-Feil
sequence.
Klippel-Trenaunay-Weber syndrome
A rare
congenital malformation syndrome of the vascular
system characterized by enlargement of a single
limb (asymmetric limb hypertrophy), varicose
veins, abnormal connections in the vasular system
(arteriovenous malformations), and abnormal
nests of blood vessels that proliferate inappropri-
ately and excessively (hemangiomata, or port-wine
stains), and pigmented moles on the skin (nevi).
Abbreviated KTW syndrome. Some sources subclas-
sify those patients with arteriovenous malformations
as having Parkes-Weber syndrome and those with
the original findings of port-wine stain, varicose
veins, and bony and soft tissue hypertrophy involv-
ing an extremity as having Klippel-Trenaunay syn-
drome. The cause of KTW syndrome is unknown.
knee
A joint that permits flexibility in the middle
of the lower extremity. The thigh bone (femur)
meets the large shin bone (tibia) to form the main
knee joint. This joint has an inner (medial) and an
outer (lateral) compartment. The kneecap (patella)
joins the femur to form a third joint, called the
patellofemoral joint. The patella protects the front
of the knee joint. The knee joint is surrounded by a
joint capsule, with ligaments strapping the inside
and outside of the joint (collateral ligaments) as
well as crossing within the joint (cruciate liga-
ments). The collateral ligaments run along the sides
of the knee and limit its sideways motion. The ante-
rior cruciate ligament (ACL) connects the tibia to
the femur at the center of the knee and functions to
limit the tibia’s rotation and forward motion. The
posterior cruciate ligament (PCL), located just
behind the ACL, limits the backward motion of the
tibia. All these ligaments provide stability and
strength to the knee joint. A thickened cartilage pad
between the two joints (meniscus) is formed by the
femur and tibia. The meniscus acts as a smooth sur-
face for the joint to move on. It serves to evenly load
the surface during weight bearing, and it also aids in
disbursing joint fluid for joint lubrication. The knee
joint is surrounded by fluid-filled sacs called bur-
sae, which serve as gliding surfaces to reduce fric-
tion of the tendons. Below the kneecap is a large
tendon (patellar tendon) that attaches to the front of
the tibia bone. Large blood vessels pass through the
area behind the knee, which is called the popliteal
space. The large muscles of the thigh move the
knee. In the front of the thigh, the quadricep mus-
cles extend the knee joint. In the back of the thigh,
the hamstring muscles flex the knee. The knee also
rotates slightly under the guidance of specific mus-
cles of the thigh. The knee is critical to normal
walking and is a weight-bearing joint. Knee pain can
be caused by a number of factors, including injury,
inflammation of the bursa (bursitis), strain, and
problems with the sciatic nerve, which runs from
the lower back to the knee. See also 
bursitis;
patellofemoral syndrome; sciatica.