Arthrofibrosis is a serious condition that can afflict
knee joints that have either been recently injured, operated upon,
or both. The process begins when the traumatic stimulus of an
injury and/or surgery leads the knee to form extensive, internal
scar tissue. This is followed by shrinkage and tightening of the
knee's joint capsule (surrounding envelope ligament). Sometimes
even nearby tendons outside of the joint stiffen up. This internal
and external tightening process may continue to the point where
motion between the femur (thigh bone) and tibia (shin bone) is
severely restricted. Afflicted patients may permanently lose the
ability to fully straighten and/or bend their knee.
In general, the likelihood of developing arthrofibrosis increases
with the severity of a knee joint injury, the extensiveness of
related surgery, and the length of time that the knee is subsequently
immobilized. However, not everyone who sustains a major knee
injury or who undergoes major surgery will develop arthrofibrosis.
Some people are more prone to developing this problem than others.
Genetic factors apparently predispose some patients to develop
arthrofibrosis by way of an inherited tendency to form hypertrophic
(excessive) internal joint scar tissue in response to injury and/or
surgery. Such individuals often heal surgical ligament repairs
and grafts quite solidly, but go on to heal "excessively",
forming an overabundance of unwanted fibrous scar in their knee.
This essentially makes their knee too stable, to the point
of being stiff and lacking proper joint motion. Such "heavy
scar-formers" can literally fill up their entire knee joint
cavity with thick, tough scar tissue. This obliterates all of
the normal open spaces within the joint, adhering everything together
and effectively "freezing" the joint (hence the traditional
term "frozen joint").
Patients with "sensitive" knees or low pain thresholds
are also more likely to develop this problem, as they find it
more difficult than most to use and move their knee after injury
or surgery. Lack of joint motion and use leads the knee to form
more abundant and less compliant scar tissue than it otherwise
would, and allows the relatively unused (and thus unstretched)
surrounding knee capsule to contract down and tighten up, almost
like "shrink-wrap" does. A stiff, arthrofibrotic
knee is a very difficult problem for the orthopedic surgeon and
physical therapist to handle. It usually requires a specially
planned, intensive protocol of surgical treatment and post-operative
management.
The traditional treatment approach for arthrofibrotic knees that
did not loosen up with aggressive stretching and exercise in physical
therapy has been to place the patient under anesthesia and then
literally break up and tear the restrictive, internal scar tissue
within the joint by forcing the knee to fully bend and
straighten. The surgeon accomplishes this by way of strenuous,
manual joint manipulation. The procedure therefore came to be
known as a manipulation under anesthesia, or "M.U.A.",
and is still in common use. In cases of severely frozen knees,
extremely stressful manipulation forces may be required
to break up the scar tissue and get the joint moving again. This
poses a risk to a patient who has not been able to bear much weight
on their leg for quite some time, because the femur and tibia
may have lost a considerable amount of bone mineral (calcium phosphate),
thus weakening them. This increases the chance of an inadvertent
femoral or tibial fracture occurring at the time of the
joint manipulation. My preference over the years has been to perform
an arthroscopic, internal surgical scar resection to remove
as much restrictive scar tissue as possible, prior to manipulating
the knee. This approach not only leaves very little scar within
the joint to re-organize and solidify once again, but it also
reduces the manipulation force required to get the knee moving,
thus reducing (but not eliminating) the chance of femoral or tibial
fracture.
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