Atlantic Orthopaedic Associates, LLC
The Hip Joint
The hip joint (fig. 1) is one of the
body’s “ball and socket” type joints. It
is comprised of the femoral head (“the
ball”) and the acetabulum (“the
socket”). Each side of the joint is lined
with cartilage. When healthy, cartilage
acts as a smooth nearly frictionless
surface which provides painless motion
between two bones at a joint.
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Arthritis (fig. 2) is a term that describes conditions where
there is disease of the cartilage resulting in cartilage
degeneration and loss, inflammation and pain. It can be a
result of life-long “wear and tear” (the most common type,
osteoarthritis). It can be a result of a previous trauma or
fracture involving the joint. Some types of arthritis can be
acquired through genetic factors or irregular anatomy (e.g.
Rheumatoid, Hip dysplasia, etc.). This lack of healthy
cartilage prevents smooth gliding of the joint and manifests
as: pain, the sense of grinding, and stiffness.
The xray in fig. 3 shows a hip joint with severe arthritis.
One can see that the ball is no longer perfectly round as it
normally is. It is, instead, oval and flattened. Also the space
between the ball and socket is obliterated which means the
cartilage is almost completely gone and this patient has
“bone on bone” arthritis. This grinding of bone on bone leads
to severe pain and the bone becoming inflammed and
sclerotic (or “chalky”). One can see on this xray how white
the bone becomes from the grinding that occurs from the
lack of cartilage.