Yoga Anatomy

skeletal sYstem 47

E5267/Kaminoff/fig3.2/417610/alw/pulled-r3

Articulating

surface of

bone

Hyaline

cartilage

Synovial fluid

Synovial

membrane

Joint

capsule

Hyaline

cartilage

Synovial fluid

Synovial

membrane

Movement in the skeletal system happens on many levels. On a cellular level, individual
cells are constantly breaking down and building up the matrix of the bone and the fi bers of
ligaments. On a tissue level, each bone and ligament has some degree of ability to change
shape in response to the forces travelling through it. On a system level, movement happens
where a relationship exists between two or more bones: the joints.

JointS

In the skeletal system the term joint describes the space where the surfaces of two or more
bones come into relationship and articulate with each other. A joint is more of an event
than a place in the sense that it depends on movement and change for its existence. If any
movement is happening, however miniscule, then there is a joint.
Conventionally, joints are classifi ed structurally by the tissue that connects the two
bones. This could be cartilage, fi brous tissue, synovial fl uid, or some combination of the
three. Joints can also be classifi ed functionally by the degree of movement possible and
biomechanically by the number of bones involved and the complexity of the joint.
In the analysis of asana, we observe movement in synovial joints, the most mobile joints
in the body. (Several of these synovial joints are also at least partly cartilaginous or fi brous.)

Synovial Joints

Starting from the center and moving outward, a synovial joint is composed of the bones
that articulate with each other, the synovial fl uid between them, the membrane that creates
that synovial fl uid, and the connective tissue that surrounds and protects
the whole structure (fi gure 3.2).
To be more specifi c, the articulating surfaces at the ends of the bones
are covered with a layer of hyaline cartilage that cushions and protects.
These layers of hyaline cartilage are slippery and allow the ends of the
bones to slide along each other with little friction.
Between these layers of hyaline cartilage, synovial fl uid acts as
a lubricant and facilitates the sliding of the articulating surfaces.
Synovial fl uid also distributes force in the joint to a slight degree,
and it acts as a fl uid seal between the two surfaces, as
oil does between two panes of glass, holding them
together. Synovial fl uid is secreted by a synovial
membrane (or synovium) that is connected to both
bones. The presence of this synovial membrane
defi nes the boundaries of the joint space: Every-
thing outside the synovial membrane is outside
the joint space.

Figure 3.2 All synovial joints have the following: articulating surfaces of bones,
hyaline cartilage, synovial fl uid, a synovial membrane (synovium), and a joint
capsule (not pictured but present in an actual knee joint is the meniscus).