Joint Counts and Rheumatoid Arthritis

Joint counts are one of the assessments healthcare providers use to establish the status of rheumatoid arthritis (RA). There are several ways to perform joint counts, but all of them involve your healthcare provider physically examining joints for pain and swelling and totaling up the number of joints that show signs of either. This information gets factored into your Disease Activity Score (DAS), which helps determine whether your RA is active or in remission.

This is important because it can help guide the treatment decisions you and your healthcare provider make. It's a look at where you are so you can figure out where to go next. For example, it could be used to compare the effectiveness of different medications. Identifying remission is especially important when making decisions about going off of your RA medication(s).

No single test or assessment is considered the gold standard for evaluating and monitoring how severe your RA is, but joint counts are considered the most specific clinical measurement for these purposes.

Your healthcare provider will use joint counts along with laboratory tests, imaging studies, functional evaluations, global measures, and patient self-report questionnaires to fully establish your disease status. (The same factors are also used to select participants for RA research studies.)

You may be able to use joint checks on your own to track the progress of your disease, but that should never replace regular check-ins with your healthcare provider.

What Are Joint Counts?

The medical community considers joint counts an important part of monitoring disease activity in RA and other forms of inflammatory arthritis, and their use is backed by research.

To examine a joint, your healthcare provider will first look at it to see if there's visible enlargement, stretched skin, or discoloration around the joint. They'll then feel it for sponginess and other signs of swelling.

They'll also compare the joints on each side. While feeling the joint, they'll ask you if it's tender or painful. You may also be asked to move a joint in a certain way to see if it hurts.

Several joint-counting methods exist, and they vary in the number of joints that are counted and how specific joints are scored. Joint-count methods include:

• 28-Joint Count (most commonly used)
• 44-Swollen Joint Count
• Ritchie Articular Index
• 66/68 Joint Count
• Thompson-Kirwan Index

Which method your healthcare provider chooses often depends on what they've been trained in or are comfortable with.

28-Joint Count

The 28-Joint Count is part of the DAS28, which is short for Disease Activity Score 28. This joint-counting method is the most common one because it's the simplest to perform. Studies have also shown that examining more joints doesn't improve accuracy.

It excludes the joints of the feet because those can be harder to assess, even with training. Included joints are:

• Shoulders
• Elbows
• Wrists
• Metacarpophalangeal (MCP) joints
• Proximal interphalangeal (PIP) joints
• Knees

To arrive at your DAS, the healthcare provider takes the number of swollen joints, the number of tender joints, results of your erythrocyte sedimentation rate (ESR) or C-reactive protein blood tests, and your global assessment of your health and feeds them into a mathematical formula to arrive at a number.

44-Swollen Joint Count and the Ritchie Articular Index

The 44-swollen joint count and the Ritchie Articular Index (RAI) are used together to determine a final DAS44 score.

A 44-Swollen Joint Count was part of the original DAS but has been largely replaced by the 28-joint count. It includes assessment of the following joints, with one point assigned for each one that is swollen:

• Sternoclavicular
• Acromioclavicular
• Shoulder
• Elbow
• Wrist
• MCP joints
• PIP joints
• Knee
• Ankle
• Metatarsophalangeal (MTP) joints

The Ritchie Articular Index assesses 52 joints for tenderness. The joints are broken into groups that are evaluated differently.

Joints in which the left and right sides are evaluated individually are:

• Shoulder
• Elbow
• Wrist
• Hip
• Ankle
• Subtalar (also called talocalcaneal, a foot joint)
• Tarsus
• Cervical spine

Joints in which the two sides are evaluated together are:

• Temporomandibular
• Sternoclavicular
• Acromioclavicular
• The MCP and PIP joints of the fingers and toes are assessed in groups

Each joint, pair, or group receives a rating from 0 to 3 as follows. The total score can range from 0 to 78.

The RAI total is added to the 44-swollen joint count total, ESR, and a general health assessment score, and that total is fed into a formula to arrive at a final DAS44 score.

66/68 Joint Count

The 66/68 Joint Count evaluates 66 joints for swelling and 68 joints for tenderness and pain with movement. (Note that the hip joints can be evaluated for tenderness only—not for swelling.)

The total score is composed of points that are based on the presence of pain and/or swelling in a joint.

Your healthcare provider then takes that total, combines it with other measures of disease activity, and puts it through a formula to arrive at a score of 1 through 10, with higher numbers indicating more disease activity.

The Thompson-Kirwan Index

The Thompson-Kirwan Index (or Thompson Articular Index) evaluates tenderness and swelling in 38 joints, while the joints are weighted according to their surface area. That means the score for the knee, which is the largest joint, counts the most.

The total score can range from 0 to 534, with higher numbers indicating more disease activity. Joints included in this index are:

• PIP joints
• MCP joints
• MTP joints
• Elbows
• Wrists
• Ankles

Using Joint Counts at Home

The goal of treatment for rheumatoid arthritis is generally to achieve and then maintain a remission of symptoms.

Often, people who are in remission see their healthcare providers less frequently than those with active and worsening symptoms. That increased time between appointments could mean you miss early signs that your disease is coming out of remission.

Self-joint counts could be a solution to that, but only if they're accurate. Studies of self-count accuracy have had mixed results. However, 2012 research focusing on the accuracy of self-counts during different stages showed that they can be quite accurate in people experiencing remission or low disease activity, while self-counts performed by people with a more active case of RA are less accurate.

The researchers suggested that rheumatologists counsel their patients in remission to perform self-counts at home as a way to detect an early upswing in disease severity.

If you have low disease activity or are in remission, you may want to talk to your healthcare provider about how to do joint counts at home. That, however, should never fully replace recommended follow-up appointments.