During NHANES III, conducted from 1988 to 1994, x-rays of hands and knees were collected on survey participants aged 60 years and older at the mobile examination center (MEC). There were no medical, safety, or other exclusions in the protocol for this component. All participants who were able to self-transfer to the x-ray table, or who could be assisted in transferring by someone who accompanied them, were eligible. There was a 93% completion rate for the hands and knees x-rays. More details can be found in the X-ray Procedures Manual: X-Ray Procedures Manual (cdc.gov).
When possible, both hands and wrists were included on a straight posterior-anterior (PA) view on one film. Similarly, both knees were included on the same film using a straight AP non-weight bearing view. The Centrix X-ray unit was used for all films. Films were processed and checked for quality by the MEC physician prior to the participant leaving the MEC.
For the original data release of NHANES III, public use data files were limited to readings by radiologists of knee osteoarthritis x-rays from phase 2 of NHANES (1991-1994) for 2,589 participants. These data include scoring for osteophyte, sclerosis and chondrocalcinosis of the knee joint. More information can be found on the NHANES III Core Data release: 11A. Knee Osteoarthritis X-Ray (October 2001).
This release provides digitized images for both phase 1 (1988-1991) and phase 2 (1991-1994) for NHANES III hand and knee x-rays. The Microtex medical grade digitizer Medi-6000 Plus was chosen for digitization of the films because it met the quality standards published by the American College of Radiology and the National Archives and supports the Digital Imaging and Communications in Medicine (DICOM) 3.0 standard.
There are 9,677 files (each contains a digitized image of a hand or knee x-ray for one participant) for 5,020 participants.
| Hand X-ray Images | Knee X-ray Images | Total X-ray Images | |
|---|---|---|---|
| Total | 4,769 | 4,908 | 9,677 |
Each eligible participant can have up to 2 hand images (depending on if hands were captured together or on separate films) and 1 knee image. Among the 5,020 participants with any x-ray images, there are:
All participants aged 60 years and older who participated in the MEC exam.
A radiologist reviewed 10% of the digitized images to ascertain that the original film quality was captured and was of sufficient diagnostic quality. Additionally, a review was performed for 10% of phase 2 knee film digitized images. Data from the original NHANES III data release on osteoarthritis grades for the phase 2 knee films were used to confirm that the same diagnostic features that were originally assessed from reading the films could be seen in the 10% sample of the digitized images.
X-ray films were digitized with the following specifications:
Images were converted to Tagged Image File Format (TIFF) using a standard lossless compression algorithm to compress the original files without losing quality. The TIFF files are 16-bit images with unchanged dimensions (length and width in pixels) from the original DICOM images. The TIFF files do not require special software to view.
File names include the participant ID, followed by “H” for hand x-ray images or “K” for knee x-ray images, and a number indicating if it is the first or, in rare cases, the second image for the participant. For example, “999H1.tiff” indicates the first hand x-ray image for participant with SEQN=999. The SEQN can have up to 5 digits and can be used to access data from the main NHANES III public use datasets for the corresponding participants.
Digitized x-ray images do not contain directly analyzable data and should be interpreted using radiological expertise with the conditions being assessed. The results of radiologic readings can be merged with the NHANES III data and subsequent analyses should use the NHANES examined sample weights. Please refer to the NHANES III documentation for additional documentation.
The current release consists of 9,677 TIFF files. Due to the quantity of the data, these files are stored at the CDC File Transfer Protocol (FTP) Server. To access, go to “Augmented Data and Special Studies” on the NHANES III (1988-1994) webpage and scroll down to “48A. Hand and Knee X-Ray Images (August 2025).” This link will take users to the FTP folder containing all 9,677 TIFF files. Users can either click the individual hyperlinks to download selected files manually or write a script in the language of their choice to download all the files together.