Q-angle and J-sign: Indicative of Maltracking Subgroups in Patellofemoral Pain
Mechanical factors related to patellofemoral pain syndrome and maltracking are poorly understood. Clinically, the Q-angle, J-sign, and lateral hypermobility commonly are used to evaluate patellar maltracking. However, these measures have yet to be correlated to specific three-dimensional patellofemoral displacements and rotations. Thus, we tested the hypotheses that increased Q-angle, lateral hypermobility, and J-sign correlate with three-dimensional patellofemoral displacements and rotations. We also determined whether multiple maltracking patterns can be discriminated, based on patellofemoral displacements and rotations. Three-dimensional patellofemoral motion data were acquired during active extension-flexion using dynamic MRI in 30 knees diagnosed with patellofemoral pain and at least one clinical sign of patellar maltracking (Q-angle, lateral hypermobility, or J-sign) and in 37 asymptomatic knees. Although the Q-angle is assumed to indicate lateral patellar subluxation, our data supported a correlation between the Q-angle and medial, not lateral, patellar displacement. We identified two distinct maltracking groups based on patellofemoral lateral-medial displacement, but the same groups could not be discriminated based on standard clinical measures (eg, Q-angle, lateral hypermobility, and J-sign). A more precise definition of abnormal three-dimensional patellofemoral motion, including identifying subgroups in the patellofemoral pain population, may allow more targeted and effective treatments.
KeywordsAnterior Knee Pain Knee Angle Lateral Patellar Patellofemoral Pain Lateral Tilt
We thank Ching-yi Shieh, PhD, and Elizabeth K. Rasch, PT, PhD, for support on the statistical analysis and Steven Stanhope, PhD, for guidance throughout the project. We also thank Bonnie Damaska, Jamie Fraunhaffer, Jere McLucas, Dr. Barry Boden, and the Diagnostic Radiology Department at the National Institutes of Health for their support and research time.
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