MCP Joint Squeeze Test and Osteoarthritis
A positive MCP joint squeeze test is NOT typically indicative of osteoarthritis and should instead raise suspicion for inflammatory arthritis, particularly rheumatoid arthritis. 1, 2
Why MCP Involvement is Atypical for Osteoarthritis
Hand osteoarthritis characteristically targets the DIP joints, PIP joints, and thumb base (CMC joint), NOT the MCP joints. 1, 2 The EULAR guidelines specifically identify only IPJ OA (interphalangeal joints) and thumb base OA as the recognized subsets of hand osteoarthritis. 2
While the guidelines acknowledge that index and middle MCP joints can occasionally be affected in hand OA, this is distinctly uncommon and represents an exception rather than the rule. 1 The prevalence of symptomatic hand OA is highest at DIP joints, followed by thumb base, then PIP joints, with MCP joints being the least commonly affected. 1
What a Positive MCP Squeeze Test Actually Indicates
The MCP squeeze test is primarily a screening tool for inflammatory arthritis, not osteoarthritis. 3, 4 Research demonstrates that:
- A positive squeeze test at the MCP joints has 53% sensitivity and 82% specificity for detecting joint swelling, with a positive likelihood ratio of 3.0 for identifying arthritis. 3
- The test correlates most strongly with joint tenderness in MCP and MTP joints and signifies moderate to high disease activity in rheumatoid arthritis patients. 4
- Tender MCP joints are primarily responsible for a positive squeeze test, and this finding is characteristic of inflammatory arthropathies. 4
Differential Diagnosis When MCP Squeeze Test is Positive
When evaluating a positive MCP squeeze test, consider these conditions in order of likelihood:
- Rheumatoid arthritis: MCP + PIP involvement with DIP sparing is the classic RA pattern, and RA mainly targets MCPs, PIPs, and wrists. 1, 2
- Psoriatic arthritis: Can affect any joint including MCPs, often asymmetrically with possible dactylitis. 1, 2
- Gout: May superimpose on pre-existing hand OA and primarily affects MCPs and wrists. 1, 5
- Hemochromatosis: Mainly targets MCPs and wrists, similar to gout. 1, 5
Key Clinical Distinctions
Look for these features to distinguish OA from inflammatory arthritis:
- Bony enlargement (Heberden's/Bouchard's nodes) suggests osteoarthritis, while soft tissue swelling indicates inflammatory arthritis. 2
- Morning stiffness <30 minutes** is typical of OA, whereas **stiffness >30 minutes characterizes inflammatory arthritis. 2
- Pain on usage that worsens with movement and improves with rest is characteristic of OA. 2
Common Pitfall to Avoid
Do not assume MCP tenderness or swelling represents osteoarthritis simply because the patient is older or has OA elsewhere. The squeeze test has insufficient sensitivity when used alone (only 53%), meaning many patients with true joint inflammation will have a negative test. 3 However, when the test is positive at the MCP joints, it strongly suggests inflammatory rather than degenerative pathology and warrants further workup including RF, anti-CCP antibodies, inflammatory markers, and consideration of plain radiographs. 1, 5