Patellar Tilt Test: Reliability and Interpretation Limitations
The patellar tilt test has poor to fair reliability with intrarater kappa coefficients of 0.44-0.50 and even worse interrater reliability with kappa coefficients of 0.20-0.35, meaning clinicians should exercise caution when using this test alone to make clinical decisions about patellofemoral malalignment. 1
Reliability Evidence
The fundamental limitation of the patellar tilt test is its inconsistency:
Intrarater reliability is only fair, with kappa values ranging from 0.44 to 0.50, meaning the same examiner testing the same patient on different occasions will get inconsistent results approximately 50% of the time 1
Interrater reliability is poor, with kappa values of 0.20-0.35, indicating different examiners frequently disagree on whether the test is positive or negative in the same patient 1
The study examining these reliability metrics included both symptomatic and asymptomatic knees (26 symptomatic, 73 asymptomatic), demonstrating that the test's unreliability persists regardless of symptom presence 1
Clinical Interpretation Challenges
Subjective Nature of the Test
The patellar tilt test relies on the examiner's tactile assessment of whether the lateral patellar edge can be elevated to neutral or beyond, which introduces significant subjectivity 1. This subjective endpoint contributes directly to the poor interrater reliability.
Lack of Standardized Training
Inter-rater reliability for radiographic measurements of patellar tilt may improve with specific formal training to calibrate observers, as demonstrated in studies showing that inexperienced assessors had particularly poor precision 2. The same principle likely applies to physical examination techniques, though the original reliability study provided only a summary document without formal hands-on training 1.
Recommended Diagnostic Approach
Given these limitations, do not rely on the patellar tilt test as a standalone diagnostic tool:
Primary Imaging Assessment
Weight-bearing axial radiographs are the gold standard for demonstrating the degree of patellar tilt or subluxation and provide superior assessment of patellofemoral kinematics compared to clinical examination 3, 4
Radiographic tilt angle measurement (angle between a line joining medial and lateral patellar edges and the horizontal) shows mean values of 12° ± 6° in patients with malalignment versus 2° ± 2° in controls, with tilt ≥5° considered abnormal 5
This radiographic measurement demonstrates 85% sensitivity and 92% specificity for detecting patellar malalignment, far superior to clinical examination 5
Advanced Imaging When Needed
MRI tilt angle ≥10° correlates strongly with significant clinical tilt, while angles <10° indicate absence of significant tilt, providing an objective measure when clinical examination is unreliable or impossible (e.g., in obese patients) 6
CT is the most commonly used modality for measuring axial malrotation when detailed assessment is required, particularly in post-arthroplasty patients 3, 7
Common Pitfalls to Avoid
Do not make treatment decisions based solely on a positive patellar tilt test given its poor reliability 1
Do not assume consistency between examiners—if multiple clinicians are involved in care, imaging confirmation is essential 1
Do not skip weight-bearing views—non-weight-bearing radiographs underestimate functional malalignment 3, 4
Be aware that quadriceps contraction can change both the type and severity of malalignment in 52% of cases, so assessment under both relaxed and contracted conditions may be necessary in difficult cases 8