238 Dance Anatomy and Kinesiology
T
his chapter will consider the knee joint and the
closely related patellofemoral joint. The knee is
the largest articulation in the body, and it is exposed
to tremendous stresses due to its location between
the very long upright bones of the lower extremity.
The knee must accept, transfer, and dissipate large
forces from above, due to body weight and the effects
of gravity, and below, from the impact associated with
weight-bearing movements. Whenever the knee is
bent while standing, gravity will tend to make it bend
further, and the photo on page 237 exemplifies the
skilled contraction of antigravity muscles required
to prevent the body from collapsing and achieve the
desired positioning of the knee. Although the associ-
ated patellofemoral joint, located just above the front
of the knee joint proper, contributes additional sta-
bility to the tibiofemoral joint, it also must withstand
very large forces. Both of these joints are vulnerable
to twisting motions, making good alignment and
technique during dance particularly important.
This chapter will present basic anatomy and
mechanics of the knee and patellofemoral joints that
influence optimal performance and the vulnerability
of this joint to injury. Topics covered will include
the following:- Bones and bony landmarks of the knee region
- Joint structure and movements of the knee
- Description and functions of individual knee
muscles - Knee alignment and common deviations
- Knee mechanics
- Structure and movements of the patellofemoral joint
- Patellofemoral alignment and the Q angle
- Patellofemoral mechanics
- Muscular analysis of fundamental knee movements
- Key considerations for the knee in whole body
movement - Special considerations for the knee in dance
- Conditioning exercises for the knee
- Knee injuries in dancers
Bones and Bony Landmarks of the Knee Region
The femur, tibia, and patella are all bones that take
part in the knee joints and patellofemoral joints.
Recall from chapter 1 that the upper leg, or thigh
bone, is termed the femur; the primary weight-
bearing bone of the lower leg is termed the tibia; and
the kneecap is termed the patella. The distal end ofthe femur is expanded with two enlargements termed
the medial and lateral condyles as shown in figure
5.1. These condyles contain the smooth articular
surfaces that rest on the upper tibia to form the knee
joint proper. You can palpate a portion of the femoral
condyles by bending your knee to 90° and then press-
ing your fingertips on the sides of the lower portion
of the patella. To help locate these articular surfaces,
repetitively slightly bend and straighten your knee
from this 90° position and feel the condyles move
under your fingertips. These condyles also bear
prominent projections to the sides that are termed
the medial and lateral epicondyles. You can locate
the epicondyles by sliding your hand down your thigh
toward the knee and finding the widest point of the
knee, at the distal portion of the femur. On the front
of the femur, between the condyles, sits a smooth,
shallow, concave surface that cannot be palpated.
It is termed the femoral groove, and it articulates
with the patella. Posteriorly, a deeper indentation
separates the medial and lateral condyles and is
termed the intercondylar fossa (L. inter, between +
condylar, condyles + fossa, trench), or intercondylar
notch (figure 5.1B).
The proximal end of the tibia is also expanded
and contains two condyles, again termed the medial
and lateral condyles. In contrast to what occurs
with the femur, the superior surfaces of these con-
dyles are relatively flat or slightly concave versus
rounded, and hence this upper surface is called
the tibial plateau. On this superior surface of the
tibia in between the flattened tibial condyles is a
roughened area termed the anterior and posterior
intercondylar areas that contains two small peaks or
projections termed the intercondylar eminence (L.
prominence). The intercondylar eminence serves
as an attachment site for ligaments and helps sta-
bilize the tibia and femur during weight bearing.
On the anterior tibia, approximately 1/2 inch (1.3
centimeters) from its proximal end are a roughened
area and projection called the tibial tuberosity (L.
tuberosus, lump), or tibial tubercle. You can easily
palpate this tuberosity by running your finger down
the middle of the kneecap and along the patellar
tendon until you feel a bump on the tibia: This is
the tibial tuberosity.
The patella is approximately triangular in shape
with its narrow apex projecting downward and
termed the inferior pole of the patella. The upper,
flatter edge of the patella is called the superior
border, and the side edges are called the medial and
lateral borders. The undersurface of the patella bears
angled surfaces termed facets, which articulate with
the underlying femur.