Muscle Strength Loss and Its Effect on Knee Cap Motion in Volunteers With Anterior Knee Pain

Chronic idiopathic patellofemoral pain, a potential precursor to osteoarthritis, is one of
the most common problems of the knee. It is characterized by anterior knee pain that is
aggravated by deep knee flexion, prolonged sitting, and repetitive flexion/extension. The
most widely accepted theory in regards to the source of this pain is that a force imbalance
around the knee leads to static patellofemoral malalignment and dynamic patellofemoral
maltracking. In turn, this malalignment and maltracking leads to elevated joint contact
stresses, which ultimately leads to patellofemoral pain. Current understanding of
patellofemoral maltracking is typically focused on static 2D alignment (lateral tilt and
displacement). Yet, patellofemoral pain is most often exacerbated during dynamic events and
the patella has complete six degrees of freedom in its movement. More recent studies have
been able to quantify patellofemoral kinematics during volitional dynamic tasks and
demonstrate that patellofemoral pain, altered kinematics are not limited to excessive
patellar lateral translation and tilt, but include excessive patellar superior translation
along with excessive flexion and valgus rotations. Flexion and valgus are sagittal and
coronal plane rotations that cause the superior pole of the patella to shift anteriorly and
medially, respectively. Recent work has shown that altered force balance around the knee can
indeed lead to maltracking. However, the question remains whether correcting an existing
force imbalance around the knee can normalize patellar kinematics and/or reduce pain. The
purpose of this study is to determine how temporary iatrogenic loss of force in the vastus
lateralis muscle alters the aberrant patellar kinematics in subjects with chronic idiopathic
patellofemoral pain.

- INCLUSION CRITERIA:

1. Male and female volunteers between the ages of 18 and 55

EXCLUSION CRITERIA:

All Volunteers

1. Any relevant medical problems, including 933 those preventing ambulation

2. Any serious injury to the joint being studied, previous surgery on the joint being
studiedor extreme pain at the joint being studied or other condition that may explain
the presence of PF_pain (e.g., meniscal tear, arthritis)

3. Allergy/hypersensitivity to any local anesthetic agent (e.g., Novocain, lidocaine,
bupivacaine, ropivacaine)

4. Liver disease

5. Open angle glaucoma

6. Cardiac arrhythmias, congenital heart disease

7. Glucose-6-phosphate dehydrogenase deficiency

8. Any female who is pregnant

A volunteer will be excluded if they have a contraindication to MR imaging. Examples are:

1. Metal within their body, which might be expected to concentrate radiofrequency fields
or cause tissue damage from twisting in a magnetic field (e.g., aneurysm clip,
implanted neural stimulator, implanted cardiac pacemaker or autodefibrillator,
cochlear implant, other foreign body (e.g. metal shavings, insulin pump).

2. A condition, which would preclude them from participating in an MR imaging study
(e.g., paralyzed hemidiaphragm, morbid obesity, severe claustrophobia)

3. A condition that presents an unnecessary risk to them or their unborn child (e.g., 953
pregnancy, previous surgery of uncertain type, symptoms of pheochromocytoma or
insulinoma)

Subjects with Chronic Idiopathic Patellofemoral Pai:

1. Lack of PF_pain (either no active pain or current pain of < 6 months duration)

Control Volunteers:

1. Any clinical signs of a knee impairment in the joint being studied, including abnormal
range of motion, muscle weakness, malalignment, and ligament damage.

2. The presence of PF_pain (either active or past)