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Knee Pain
What is in common?
Observe what?
One of the Most Running Injuries
Patellofemoral Pain Syndrome
("Runner's Knee")
Anatomy
Patellofemoral Pain
• A common misconception is that the patella only moves in
an up-and-down direction. In fact, it also tilts and rotates, so
there are various points of contact between the
undersurface of the patella and the femur.2,3
• Repetitive contact at any of these areas, sometimes
combined with maltracking of the patella that is often not
detectable by the naked eye, is the likely mechanism of
patellofemoral pain syndrome.
• The result is the classic presentation of retropatellar and
peripatellar pain.
Causes
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patellofemoral pain syndrome (PFPS), or simply "runner's knee," is the most
common overuse injury among runners.
It occurs when a mistracking kneecap (patella) irritates the femoral groove in
which it rests on the thighbone.
It could be a biomechanical problem—the patella may be larger on the outside
than it is on the inside,
it may sit too high in the femoral groove, or it may dislocate easily. Also, worn
cartilage in the knee joint reduces shock absorption,
high-arched feet provide less cushioning, and flat feet or knees that turn in or out
excessively can pull the patella sideways.
There are also muscular causes. Tight hamstring and calf muscles put pressure on
the knee, and weak quadriceps muscles can cause the patella to track out of
alignment.
Just the repetitive force of a normal running stride alone can be enough to
provoke an attack.
Causes
• Several anatomic and congenital factors may lead to a
predisposition towards patellofemoral pain and/or instability.
• Tightness of the quadriceps muscles, hamstrings and iliotibial
band, and relative weakness of the quadriceps muscle are
probably the most common causes.
• Other factors that can contribute to this problem include femoral
anteversion (excessive rotation of the hips), tibial torsion
(excessive rotation of the shin bone), genu valgum (knock knees),
genu recurvatum (hyperextended knee) and excessive pronation
(flat feet).
Etiology
• Weakness of the quadriceps
• Weakness of the medial quadiceps, specifically VMO dysplasia
• Tight iliotibial bands
• Tight hamstring muscles
• Weakness or tightness of the hip muscles (adductors, abductors,
external rotators)
• Tight calf muscles
scular Etiologies of Patellofemoral Pain
Syndrome and Their Pathophysiology
Etiology
Pathophysiology
Weakness of the quadriceps
The "quads" include the vastus medialis, vastus medialis obliquus (VMO), vastus intermedius, vastus lateralis
and rectus femoris. Weakness may adversely affect the patellofemoral mechanism. Quad-muscle strengthening
is often recommended.3,4,7,9,10,14-17
Weakness of the medial quadiceps,
specifically VMO dysplasia
Weakness of the VMO allows the patella to track too far laterally. Although the role of the VMO is
controversial,18-20 VMO strengthening is often recommended.6,7,11,15,16 However, the VMO is a difficult muscle to
isolate,21 and most patients find general quadriceps strengthening easier to accomplish.
Tight iliotibial bands
A tight iliotibial band places excessive lateral force on the patella and can also externally rotate the tibia,
upsetting the balance of the patellofemoral mechanism.22,23 This problem can lead to excessive lateral tracking
of the patella.
Tight hamstring muscles
The hamstring muscles flex the knee. Tight hamstrings place more posterior force on the knee, causing pressure
between the patella and femur to increase.7,15,16
Weakness or tightness of the hip muscles
(adductors, abductors, external rotators)
The VMO originates on the adductor magnus tendon. This is the anatomic basis for recommending adductor
strengthening.11,14,16Abductor (gluteus medius) strengthening helps to stabilize the pelvis. Dysfunction of the hip
external rotators results in compensatory foot pronation; a simple stretch can improve muscular efficiency. 4
Tight calf muscles
Tight calves can lead to compensatory foot pronation and, like tight hamstrings, can increase the posterior force
on the knee.11,15,16
NOTE: Exercises to treat the various
muscular causes are illustrated in thepatient
information handout that follows this article.
Information from references 3, 4, 6, 7, 9
through 11, and 14 through 23.
Malalignment
Q angle
• Angle. Although some investigators believe that a "large" Q angle
(Figure 3) is a predisposing factor for patellofemoral pain, others
question this claim.
• One study12 found similar Q angles in symptomatic and
nonsymptomatic patients.
•
• Another study6 compared the symptomatic and asymptomatic
legs in 40 patients with unilateral symptoms and found similar Q
angles in each leg.
•
Furthermore, "normal" Q angles vary from 10 to 22
degrees,3depending on the study, and measurements of the Q
angle in the same patient vary from physician to physician.13
Foot Overpronation
chondromalacia patella
Normally, the hyaline cartilage
on the back surface of the
patella is thicker than anywhere
else in the body.
Problems with the cartilage on
the back of the patella include
softening, blistering, fissuring,
erosion, and thinning.
These problems are collectively
called chondromalacia patella.
• The top view is called
a "Merchant's view" and
is obtained with the knee
bent 45-degrees, with the
beam of the X-ray
photograph directed
through the knee from
head to toe. It shows
how well the patella is
aligned within the groove
on the femur, called
the trochlear groove
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A high-riding patella is
called patella alta, and
can be associated with
instability of the patella,
as it is not well-engaged
in the trochlear sulcus
with the knee near full
extension (straight). A
• low-riding patella is
called patella baja.
Treatment
• Many cases of mild to moderate chondromalacia patella can be treated with
just oral anti-inflammatory medication, weight loss and the proper type of
therapeutic exercise.
•
While nutritional supplements such as glucosamine and chondroitin have
been shown to ease arthritic joint discomfort and slow down articular
cartilage breakdown in some patients, there is no convincing proof yet that
they totally halt or reverse chondromalacia.
• Viscosupplementation(Synvisc, Hyalgan, etc.) injection treatment does not
seem to work as well on patellar arthritis pain as it does on symptoms
caused by arthritic joint surfaces elsewhere in the knee.
Core Strengthening
•
An 8-week rehabilitation
program focusing on
strengthening and
improving neuromuscular
control of the hip and core
musculature produces
positive patient outcomes,
improves hip and core
muscle strength, and
reduces the knee abduction
moment, which is
associated with developing
PFPS.
Knee Flexion
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Previous research has been
done to indicate that in a
closed chain setting, knee
flexion beyond 60 degrees
leads to increased
patellofemoral joint
compression and this may be
contraindicated for those with
PFJ pain or chondromalacia.
• Also keep in mind that most
people with PFJ complain of
more pain descending stairs
than ascending stairs.
Knee Flexion
VMO
• The VM has an important role as
a medial stabilizer of the patella
and aids in the normal
functioning of the PFJ.
• The VM is phylogenetically the
weakest of the quadriceps group
and appears to be the first
muscle to atrophy and the last to
rehabilitate
• Quadriceps strengthening
exercises, emphasizing the VM,
have been suggested as the
primary initial management of
patellofemoral disorders
VMO Exercises
Rehabilitation
• Rest
• Ice
• Stretching (quads, hamstrings, IT band and hip musculature)
• Straight leg raises
• Short arc quads (mini-knee extensions from 30-0 degrees if you will on a
bolster) although I am not a huge fan of these
• Mini-squats
• Calf raises
Surgery