Chondromalacia patella should not be confused with simple patellar
arthralgia ("achy kneecap syndrome", for lack of
a better common name), which causes a dull, achy pain within the
kneecap bone itself. This pain makes it difficult to keep one's
knee flexed (bent) for prolonged periods, such as in movie theaters
or airplanes. While this syndrome can co-exist with patellar chondromalacia,
it can cause symptoms even when the articular cartilage behind
the kneecap is perfectly firm and healthy. Patellar arthralgia,
by itself, is usually recognizable as such by knee specialists.
It is usually best treated with therapeutic exercise alone, emphasizing
quadriceps muscle strengthening and stretching. Surgery rarely
offers any benefit.
When knee pain is caused by structural softening and degeneration
of the articular cartilage behind the kneecap (true chondromalacia),
the patient's orthopedic surgeon should search for underlying
mechanical causes such as natural patellar malalignment, a history
of recurrent injury caused by unstable (loose) kneecaps and/or
a history of prior, severe impact injury to the patella.
Surgeons should assess their patients with patellar pain by
performing a careful physical examination, looking for patellar
articular surface tenderness, crepitation, or problems such as
patellar arthralgia, infrapatellar tendinitis, patellar instability,
or malalignment caused by an excessively tight lateral retinaculum.
The lateral retinaculum is a sheet of tough, ligament-like tissue
connecting the lateral (outer) aspect of the patella to the lateral
femur. It is usually thicker and better developed than its matched
counterpart on the medial (inner) side of the knee, the medial
patellar retinaculum. An excessively tight lateral retinaculum
pulls the kneecap over toward the outside of the knee, creating
excessive pressure between the lateral aspect of the patella and
the lateral femur. This in turn may cause premature breakdown
of the articular (joint surface) cartilage there. This type of
malalignment syndrome is known as "ELPS" or excessive
lateral pressure syndrome, and can usually be confirmed by
special x-ray studies.