The purpose of the study is to use different x-ray and magnetic resonance (MR) imaging techniques to take pictures of the knee. There are two specific purposes to the study:

1. whether the different x-ray and MRI techniques will give the same or different information about the knee joint and
2. which part of the knee joint will show the biggest change using the different x-ray and MRI techniques. The study is not designed to test a hypothesis.

Inclusion Criteria:

• Female
• 40 years and older
• Subjects who are willing and able to comply with x-ray and MRI procedures
• Evidence of a personally signed and dated consent document

Additional inclusion for normal controls:

• Infrequent knee pain, aching, or stiffness during the past year or infrequent use of medication for treatment of knee pain during the past year
• No evidence of OA on either knee (i.e. K-L grade = 0 diagnosed by knee radiography)

Additional inclusion for OA patients:

• Pain, aching, or stiffness on most days of a month during the past year; or use of medication for treatment of knee pain on most days of a month during the past year
• Kellgren-Lawrence Grade 2 or 3 of the study knee obtained on a Standard knee radiograph (with either the same or less severe OA, or no OA in the contralateral knee)

Exclusion Criteria:

• Subject is unable to undergo MRI because of contraindication
• Women at risk of pregnancy
• Weight greater than 250 lbs
• History of surgery in the study knee
• History of other diseases involving the study knee joint including inflammatory joint diseases, crystalline disease, and infection of the study knee

Female, 40 years and older, community sample