What Are Joint Counts?

Tracking the Number of Swollen and Tender Joints

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Rheumatoid arthritis is a chronic, systemic, inflammatory disease. Its presentation, as well as the course of the disease, is variable within an individual patient and between different patients. Swollen and tender joints are characteristics of active rheumatoid arthritis.

There is no single quantitative test or assessment that is considered the gold standard for evaluating and monitoring the clinical status of rheumatoid arthritis patients.

There are, instead, various assessments used to establish patient status in the clinical setting and for research purposes, including joint counts, laboratory tests, imaging studies, functional evaluations, global measures, and patient self-report questionnaires.

Joint counts are considered the most specific quantitative clinical measure used to assess the status of patients with inflammatory types of arthritis, especially rheumatoid arthritis. Joints counts are also a significant part of Disease Activity Scores (DAS), the American College of Rheumatology Core Data Set for rheumatoid arthritis clinical trials, and the American College of Rheumatology remission criteria.

Joint Count Methods

There are several joint counts. The methods vary in the number of joints that are counted and how a specific joint is scored. Joint count methods include the 66/68 Joint Count, The Ritchie Articular Index, The Thompson-Kirwan Index, 44-Swollen Joint Count, and the 28-Joint Count.

66/68 Joint Count

The 66/68 Joint Count evaluates 66 joints for swelling and 68 joints for tenderness and pain with movement. The temporomandibular, sternoclavicular, acromioclavicular, shoulder, elbow, wrist, metacarpophalangeal (MCP), proximal interphalangeal (PIP), distal interphalangeal (DIP), hip, knee, ankle, tarsus, metatarsophalangeal (MTP), and interphalangeal of the feet are included in this joint count.

Hip joints can be evaluated for tenderness only -- but not for swelling.

The Ritchie Articular Index

The Ritchie Articular Index assesses 52 joints. The shoulder, elbow, wrist, hip, ankle, talocalcaneal, tarsus, and cervical spine are evaluated for tenderness only. MCP and PIP joints are assessed in groups. Right and left joints are evaluated together in the temporomandibular, sternoclavicular, and acromioclavicular joints. This index involves grading: 0=nontender, 1=tender, 2=tender with wincing, 3=tender with wincing and withdrawal. The total score can range from 0 to 78.

The Thompson-Kirwan Index

The Thompson-Kirwan Index evaluates tenderness and swelling in 38 joints. The joints are weighted according to their surface area. The total score can range from 0-534. The knee is weighted more than other joints. The PIP, MCP, MTP joints, elbows, wrists, and ankles are included in this index.

44-Swollen Joint Count

A 44-Swollen Joint Count is part of the original DAS (Disease Activity Score). The sternoclavicular, acromioclavicular, shoulder, elbow, wrist, MCP, PIP, knee, ankle, and MTP joints are included in this joint count.

28-Joint Count

The 28-Joint Count is part of the DAS28. Shoulders, elbows, wrists, MCP, PIP, and knees are included in the 28-Joint Count. Joints of the feet are excluded.

The Bottom Line

While the Ritchie Articular Index utilizes a grading system for scoring and Thompson-Kirwan uses a weighted scoring system, the other three joint counts described above count the abnormal joints without grading the severity of swelling or tenderness.

While the usefulness of joint counts in clinical trials is not disputed, in routine clinical practice the significance of joint counts is questioned by some, largely due to the complexity and difficulty of performing the counts. The American College of Rheumatology (ACR) does include joint counts in their recommendations for clinical care, however.

The 28-Joint Count includes the most commonly affected joints, and its results correlate well with the 66/68 Joint Count. Due to its simplicity and reliability, the 28-Joint Count is considered the preferred joint count method.

Sources:

Joint Assessment in Rheumatoid Arthritis. D.L. Scott and D.A. Houssien. British Medical Journal 1996;35(supplement 2):14-18.
http://rheumatology.oxfordjournals.org/content/35/suppl_2/14.full.pdf

Joint Counts. Ozlem Pala, M.D. and L. Frank Cavaliere, M.D. Chapter 7.
http://www.rheumatology.org/assets/0/116/401/408/419/420/d49d771a-8035-469f-b7a4-65838f9fcfef.pdf

Joint Counts in Routine Practice. Oxford Journals. Rheumatology.  D.L. Scott et al. 2003;42(8).
http://rheumatology.oxfordjournals.org/content/42/8/919.full

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