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