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Background: Patellofemoral pain syndrome is a prevalent condition in young people. While it is widely believed that abnormal patellar tracking plays a role in the development of patellofemoral pain syndrome, this link has not been established. The purpose of this cross-sectional case-control study was to test the hypothesis that patterns of patellar spin, tilt, and lateral translation make it possible to distinguish individuals with patellofemoral pain syndrome and clinical evidence of patellar malalignment from those with patellofemoral pain syndrome and no clinical evidence of malalignment and from individuals with no knee problems.
Methods: Three-dimensional patellofemoral joint kinematics in one knee of each of sixty volunteers (twenty in each group described above) were assessed with use of a new, validated magnetic resonance imaging-based method. Static low-resolution scans of the loaded knee were acquired at five different angles of knee flexion (ranging between –4° and 60°). High-resolution geometric models of the patella, femur, and tibia and associated coordinate axes were registered to the bone positions on the low-resolution scans to determine the patellar motion as a function of knee flexion angle. Hierarchical modeling was used to identify group differences in patterns of patellar spin, tilt, and lateral translation.
Results: No differences in the overall pattern of patellar motion were observed among groups (p > 0.08 for all global maximum likelihood ratio tests). Features of patellar spin and tilt patterns varied greatly between subjects across all three groups, and no significant group differences were detected. At 19° of knee flexion, the patellae in the group with patellofemoral pain and clinical evidence of malalignment were positioned an average of 2.25 mm more laterally than the patellae in the control group, and this difference was marginally significant (p = 0.049). Other features of the pattern of lateral translation did not differ, and large overlaps in values were observed across all groups.
Conclusions: It cannot be determined from our cross-sectional study whether the more lateral position of the patella in the group with clinical evidence of malalignment preceded or followed the onset of symptoms. It is clear from the data that an individual with patellofemoral pain syndrome cannot be distinguished from a control subject by examining patterns of spin, tilt, or lateral translation of the patella, even when clinical evidence of mechanical abnormality was observed.
Clinical Relevance: Since most patients with patellofemoral pain syndrome did not demonstrate abnormalities in patellar tracking during loaded knee flexion, other causative mechanisms must be explored to develop effective diagnostic and treatment strategies for this common musculoskeletal condition.
Re: Patella tracking and patellofemoral pain syndrome
Patellar Maltracking Correlates With Vastus Medialis Activation Delay in Patellofemoral Pain Patients
Saikat Pal, Christine E. Draper, Michael Fredericson, Gary E. Gold, Scott L. Delp, Gary S. Beaupre, Thor F. Besier American Journal of Sports Medicine
Background: Delayed onset of vastus medialis (VM) activity compared with vastus lateralis activity is a reported cause for patellofemoral pain. The delayed onset of VM activity in patellofemoral pain patients likely causes an imbalance in muscle forces and lateral maltracking of the patella; however, evidence relating VM activation delay to patellar maltracking is sparse. The aim of this study was to investigate the relationship between VM activation delay and patellar maltracking measures in pain-free controls and patellofemoral pain patients.
Hypothesis: Patellar tilt and bisect offset, measures of patellar tracking, correlate with VM activation delay in patellofemoral pain patients classified as maltrackers.
Study Design: Case control study; Level of evidence, 3.
Methods: Vasti muscle activations were recorded in pain-free (n = 15) and patellofemoral pain (n = 40) participants during walking and jogging. All participants were scanned in an open-configuration magnetic resonance scanner in an upright weightbearing position to acquire the position of the patella with respect to the femur. Patellar tilt and bisect offset were measured, and patellofemoral pain participants were classified into normal tracking and maltracking groups.
Results: Correlations between VM activation delay and patellar maltracking measures were statistically significant in only the patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset (R 2 = .89, P < .001, with patellar tilt during walking; R 2 = .75, P = .012, with bisect offset during jogging). There were no differences between the means of activation delays in pain-free and all patellofemoral pain participants during walking (P = .516) or jogging (P = .731).
Conclusion: There was a relationship between VM activation delay and patellar maltracking in the subgroup of patellofemoral pain participants classified as maltrackers with both abnormal tilt and abnormal bisect offset.
Clinical Relevance: A clinical intervention such as VM retraining may be effective in only a subset of patellofemoral pain participants—namely, those with excessive tilt and excessive bisect offset measures. The results highlight the importance of appropriate classification of patellofemoral pain patients before selection of a clinical intervention.
Research presented in August at the annual meeting of the American Society of Biomechanics in Long Beach, CA, adds support to the increasingly popular idea that patellofemoral pain syndrome arises from different mechanisms—and therefore should be managed differently—in different subgroups of patients.
The findings also call into question the popular theory that patellar maltracking stems primarily from strength or activation imbalances in the vasti muscles. They suggest instead that vasti function is only one of multiple factors contributing to patellar maltracking, and it’s the other factors that may prove more useful for differentiating one PFPS subgroup from another.
Re: Patella tracking and patellofemoral pain syndrome
Electromechanical Delay of the Vastus Medialis Obliquus and Vastus Lateralis in Individuals With Patellofemoral Pain Syndrome
Han-Yu Chen, Chia-Chen Chien, Shyi-Kuen Wu, Jiann-Jong Liau, Mei-Hwa Jan J Orthop Sports Phys Ther 2012;42(9):791-796,
STUDY DESIGN: Case-control study.
OBJECTIVE: To examine electromechanical delay (EMD) of the vastus medialis obliquus (VMO) and the vastus lateralis (VL) in individuals with patellofemoral pain syndrome (PFPS).
BACKGROUND: EMD is a mechanical property of muscles related to protective reflex and sports performance. The time duration of the EMD can be shortened with strength training and, conversely, can be lengthened secondary to immobilization. However, it is unclear if EMD between various components of the quadriceps is affected in individuals with PFPS.
METHODS: Twenty-six individuals with PFPS and 26 healthy volunteers were studied. The VMO and VL were electrically stimulated to evoke muscle twitches. Ultrasound was used to assess patellar movement elicited by the muscle twitch. The time from the onset of electrical stimulation to the onset of patellar movement was measured as the EMD. The EMDs of the VMO and VL were compared between groups using a mixed-model analysis of variance.
RESULTS: Subsequent to a significant interaction (P<.001), post hoc analysis indicated that the EMD of the VMO was longer (PFPS, 37.3 ± 0.7 milliseconds; control, 25.9 ± 0.7 milliseconds; P<.001) and the EMD of the VL was shorter (PFPS, 18.4 ± 0.5 milliseconds; control, 25.1 ± 0.5 milliseconds; P<.001) in the PFPS group. Therefore, in the individuals with PFPS, the EMD of the VMO was significantly longer than that of the VL (P<.001), which was not the case for those in the control group (P = .20).
CONCLUSION: The mechanical properties of the VMO and VL may be altered in patients with PFPS.
Purpose: A dysfunction of the quadriceps muscle group has often been suggested to play an important role in the pathophysiology of patellofemoral pain (PFP). However, consensus is lacking regarding the quadriceps recruitment pattern of patients with PFP. The aim of this study is to examine by muscle functional magnetic resonance imaging (mfMRI) if PFP patients actually exhibit an altered activation of the muscles that play a significant role in the dynamic balance of the patella.
Methods: Forty-six patients with PFP (25 female and 21 male, mean age 25.0 +/- 7.4 years) and 30 healthy control subjects (17 female and 13 male, mean age 21.6 +/- 4.5 years) underwent MRI of the quadriceps before and immediately after a squat exercise. The transverse relaxation time (T2) and the T2 shift were calculated for the vasti muscles.
Results: There were no significant differences in the T2 values at rest and the T2 shift values between the patient and the control group, except for the T2 rest value of the VMVI of females (P=0.007). The T2 shift of the VL was significantly smaller than the T2 shift of the VMVI in both study groups (male P<0.001 and female P=0.044), while in females, the T2 shift of the VMO was also significantly smaller than the T2 shift of the VMVI (P=0.027).
Conclusions: The activation pattern of the quadriceps is not altered in patients with PFP for both males and females. As the relative contribution of the quadriceps muscles to a functional activity has not been modified, there is no evidence for quadriceps dysfunction.
To investigate the extent to which quadriceps muscle activation and strength are responsible for patellofemoral pain.
A pain on–off switch system synchronized with a force transducer and surface electromyography was utilized on 32 volunteer patellofemoral pain patients during maximal isometric and squat exercises.
There were 26 patients out of the 32 tested who complained of pain during the squat or isometric test, of these 20 subjects presented a significant advantage for the vastus lateralis compared to the vastus medialis obliquis activation and 12 patients had decreased quadriceps strength of the symptomatic compared to the non symptomatic leg. All patients who demonstrated weak vastus medialis obliquis activation during the isometric exercise possessed the same symptoms during the squat. On the other hand, 9 patients who showed diminished vastus medialis obliquis activation during the squat displayed equal activation between the vastus medialis obliquis and the vastus lateralis during the isometric task. With regard to the timing for the onset of muscle activation, there were only 4 patients who had a difference (P = 0.03) between the symptomatic (0.042 s) and non-symptomatic legs (0.011 s).
Causes for patellofemoral pain vary and are not necessarily a result of quadriceps strength deficit or vastus medialis obliquis activation weakness. Patellofemoral pain patients who possess lower vastus medialis obliquis activation compared to the vastus lateralis do not necessarily have quadriceps weakness while patients presenting with quadriceps strength deficits do not always have an imbalance between vastus medialis obliquis and vastus lateralis activation.