What laboratory tests should be obtained for a patient with hip pain that improves with movement but worsens at night?

Laboratory Findings in Hip Pain Relieved by Activity and Worsening at Night

In a patient with hip pain that improves with movement but worsens at night, you should obtain inflammatory markers (ESR and CRP), as this pain pattern strongly suggests inflammatory arthropathy, particularly axial spondyloarthropathy or inflammatory joint disease, rather than mechanical osteoarthritis. 1

Key Clinical Context

The specific pain pattern described—relief with activity and worsening at night—is a red flag for inflammatory conditions rather than degenerative disease. 1 This is the opposite pattern of typical osteoarthritis, where pain worsens with activity and improves with rest. 2

Pain Pattern Significance

• Night pain in hip disease correlates strongly with joint effusion and active inflammation 3
• In rheumatoid arthritis, nocturnal pain specifically correlates with swollen joints (p < 0.001) and elevated CRP (p < 0.005), indicating active inflammatory disease 4
• Pain improved by exercise and not relieved by rest, especially when worse in the latter part of the night, should trigger investigation for axial spondyloarthropathy 1

Recommended Laboratory Tests

Essential Inflammatory Markers

• ESR (Erythrocyte Sedimentation Rate): Elevated ESR suggests inflammatory arthropathy; ESR <20 mm/hour helps distinguish osteoarthritis from inflammatory conditions 2
• CRP (C-Reactive Protein): Correlates with active joint inflammation and nocturnal pain in inflammatory arthritis 4

Additional Testing Based on Clinical Suspicion

For patients under 45 years with this pain pattern lasting >3 months:

• HLA-B27 testing should be considered for axial spondyloarthropathy, though it is less often positive in IBD-associated axial arthropathy 1
• Complete blood count to assess for anemia and systemic inflammation 1
• Vitamin D and B12 levels in patients with inflammatory bowel disease 1

When to Suspect Inflammatory Arthropathy

The British Society of Gastroenterology specifically identifies this constellation as concerning for axial spondyloarthropathy when present in young people (under 45 years): 1

• Low back/hip pain for >3 months
• Improved with exercise
• Not relieved by rest
• Worse in the latter part of the night
• Morning stiffness lasting >30 minutes

Critical Diagnostic Pitfalls

Do not rely on laboratory tests alone—imaging must be combined with symptoms and clinical signs. 1 However, the laboratory findings help distinguish inflammatory from mechanical causes:

• ESR <45 mm/hour combined with limited hip internal rotation (<15°) suggests osteoarthritis rather than inflammatory disease 2
• Elevated inflammatory markers with this specific pain pattern mandate rheumatology referral and MRI evaluation 1

Urgent Considerations

• If septic arthritis is suspected, urgent joint aspiration is required before any other workup 5
• Check coagulation studies before invasive procedures if hemarthrosis is suspected 5

Imaging Correlation

While the question asks about laboratory findings, note that plain radiographs of the spine and sacroiliac joints will miss most early inflammatory disease in this clinical scenario. 1 MRI scanning (sagittal images of cervicothoracic and thoracolumbar regions with T1 and STIR sequences, and coronal/oblique sacroiliac joints) should be obtained alongside laboratory testing. 1

The combination of elevated inflammatory markers (ESR/CRP) with this characteristic pain pattern should prompt immediate rheumatology referral and advanced imaging, as early diagnosis and treatment with physiotherapy and anti-TNF agents can prevent long-term disability. 1