X-ray of osteoarthritis of the knee

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Author: Mikael Häggström [notes 1]
X-ray of osteoarthritis of the knee:



Generally standing AP (Wikiradiography) and lateral images. Supine position is preferable in some pre-operative situations to better visualize the cartilage.


The main objective is to grade the severity of osteoarthritis. The International Knee Documentation Committee (IKDC) system is regarded to have the most favorable combination of interobserver precision and correlation to knee arthroscopy findings.[1] It was formed by a group of knee surgeons from Europe and America who met in 1987 to develop a standard form to measure results of knee ligament reconstructions.[2]

The Ahlbäck system has been found to have comparable interobserver precision and arthroscopy correlation to the IKDC system, but most of the span of the Ahlbäck system focused at various degrees of bone defect or loss, and it is therefore less useful in early osteoarthritis.[1] Systems that have been found to have lower interobserver precision and/or arthroscopy correlation are those developed by Kellgren-Lawrence, Fairbank, Brandt, and Jäger-Wirth.[1]

International Knee Documentation Committee (IKDC) system[1]
Grade Findings
A No joint space narrowing, defined in this system as at least 4 mm joint space
B At least 4 mm joint space, but small osteophytes, slight sclerosis, or femoral condyle flattening
C 2–4 mm joint space
D <2 mm joint space
Ahlbäck classification[3]
Grade Findings
I Joint space narrowing, with or without subchondral sclerosis. Joint space narrowing is defined by this system as a joint space less than 3 mm, or less than half of the space in the other compartment, or less than half of the space of the homologous compartment of the other knee.
II Obliteration of the joint space
III Bone defect/loss <5 mm
IV Bone defect/loss between 5 and 10 mm
V Bone defect/loss >10 mm, often with subluxation and arthritis of the other compartment

For the patellofemoral joint, a classification by Merchant 1974 uses a 45° "skyline" view of the patella:[4]

Merchant system
Stage Description
1 (mild) Patellofemoral joint space > 3mm
2 (moderate Joint space < 3 mm but no bony contact
3 (severe) Bony surfaces in contact over less than one quarter of the joint surface
4 (very severe) Bony contact throughout the entire joint surface


A subjective grading of osteoarthritis is generally warranted, such as mild, moderate or severe, which may correspond to grades B, C, D, respectively, of the IKDC system. In Swedish practice, such subjective grading is regarded as sufficient to report for osteoarthritis, since the management of the disease depends on symptoms rather than the exact grading of imaging findings.[5]

See also: General notes on reporting

See also


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Radlines:Authorship for details.


  1. 1.0 1.1 1.2 1.3 "Osteoarthritis Classification Scales: Interobserver Reliability and Arthroscopic Correlation ". The Journal of Bone and Joint Surgery. American Volume 96 (14): 1145–1151. 2014. doi:10.2106/JBJS.M.00929. ISSN 0021-9355. 
  2. Hefti F, Müller W, Jakob RP, Stäubli HU (1993). "Evaluation of knee ligament injuries with the IKDC form. ". Knee Surg Sports Traumatol Arthrosc 1 (3-4): 226–34. doi:10.1007/bf01560215. PMID 8536037. Archived from the original. . 
  3. Hernández-Vaquero, Daniel; Fernández-Carreira, José Manuel (2012). "Relationship between radiological grading and clinical status in knee osteoarthritis. a multicentric study ". BMC Musculoskeletal Disorders 13 (1). doi:10.1186/1471-2474-13-194. ISSN 1471-2474. 
  4. Kim, Young-Mo; Joo, Yong-Bum (2012). "Patellofemoral Osteoarthritis ". Knee Surgery & Related Research 24 (4): 193–200. doi:10.5792/ksrr.2012.24.4.193. ISSN 2234-0726. 
  5. . Total knee arthroplasty. UpToDate. This topic last updated: Apr 01, 2019.