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 extensionflexion 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.

We retrospectively reviewed 21 patients (22 shoulders) who presented with deep infection after surgery to the shoulder, 17 having previously undergone hemiarthroplasty and five open repair of the rotator cuff. Nine shoulders had undergone previous surgical attempts to eradicate their infection. The diagnosis of infection was based on a combination of clinical suspicion (16 shoulders), positive frozen sections (> 5 polymorphonuclear leukocytes per high-power field) at the time of revision (15 shoulders), positive intra-operative cultures (18 shoulders) or the pre-operative radiological appearances. The patients were treated by an extensive debridement, intravenous antibiotics, and conversion to a reverse shoulder prosthesis in either a single- (10 shoulders) or a two-stage (12 shoulders) procedure. At a mean follow-up of 43 months (25 to 66) there was no evidence of recurrent infection. All outcome measures showed statistically significant improvements. Mean abduction improved from 36.1 degrees (sd 27.8) pre-operatively to 75.7 degrees (sd 36.0) (p < 0.0001), the mean forward flexion from 43.1 degrees (sd 33.5) to 79.5 degrees (sd 43.2) (p = 0.0003), and mean external rotation from 10.2 degrees (sd 18.7) to 25.4 degrees (sd 23.5) (p = 0.0037). There was no statistically significant difference in any outcome between the single-stage and the two-stage group.

Patellofemoral pain is widely accepted as one of the most common pathologies involving the knee, yet the etiology of this pain is still an open debate. Generalized joint laxity has been associated with patellofemoral pain, but is not often discussed as a potential source of patellar maltracking. Thus, the objective of this study was to compare the complete 6 degree of freedom patellofemoral and tibiofemoral kinematics from a group of patients diagnosed with patellofemoral pain syndrome and maltracking to those from an asymptomatic population. The following null hypotheses were tested: kinematic alterations in patellofemoral maltracking are limited to the axial plane; knee joint kinematics are the same in maltrackers with and without generalized joint laxity (defined by a clinical diagnosis of Ehlers Danlos Syndrome); and no correlations exist between tibiofemoral and patellofemoral kinematics or within patellofemoral kinematics. This study demonstrated that alterations in patellofemoral kinematics, associated with patellofemoral pain, are not limited to the axial plane, minimal correlations exist between patellofemoral and tibiofemoral kinematics, and distinct subgroups likely exist within the general population of maltrackers. Being able to identify subgroups correctly within the omnibus diagnosis of patellar maltracking is a crucial step in correctly defining the pathophysiology and the eventual treatment of these patients.

The inferior shift in patellar displacement with taping partially explains the previously documented decrease in pain due to increases in contact area. The lack of alteration in 5 of the 6 kinematic variables with taping may have been due to the fact that post-taping kinematic alterations are sensitive to the baseline kinematic values.