Patients with patellofemoral pain exhibit elevated bone metabolic activity at the patellofemoral joint

Department of Radiology, Stanford University, Stanford, California, USA.
Journal of Orthopaedic Research (Impact Factor: 2.97). 02/2012; 30(2):209-13. DOI: 10.1002/jor.21523
Source: PubMed

ABSTRACT Patellofemoral pain is characterized by pain behind the kneecap and is often thought to be due to high stress at the patellofemoral joint. While we cannot measure bone stress in vivo, we can visualize bone metabolic activity using (18) F NaF PET/CT, which may be related to bone stress. Our goals were to use (18) F NaF PET/CT to evaluate whether subjects with patellofemoral pain exhibit elevated bone metabolic activity and to determine whether bone metabolic activity correlates with pain intensity. We examined 20 subjects diagnosed with patellofemoral pain. All subjects received an (18) F NaF PET/CT scan of their knees. Uptake of (18) F NaF in the patella and trochlea was quantified by computing the standardized uptake value and normalizing by the background tracer uptake in bone. We detected increased tracer uptake in 85% of the painful knees examined. We found that the painful knees exhibited increased tracer uptake compared to the pain-free knees of four subjects with unilateral pain (P = 0.0006). We also found a correlation between increasing tracer uptake and increasing pain intensity (r(2)  = 0.55; P = 0.0005). The implication of these results is that patellofemoral pain may be related to bone metabolic activity at the patellofemoral joint.

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    ABSTRACT: Asymmetry in the alignment of the lower limbs during weight-bearing activities is associated with patellofemoral pain syndrome (PFPS), caused by an increase in patellofemoral (PF) joint stress. High neuromuscular demands are placed on the lower limb during the propulsion phase of the single leg triple hop test (SLTHT), which may influence biomechanical behavior. The aim of the present cross-sectional study was to compare kinematic, kinetic and muscle activity in the trunk and lower limb during propulsion in the SLTHT using women with PFPS and pain free controls. The following measurements were made using 20 women with PFPS and 20 controls during propulsion in the SLTHT: kinematics of the trunk, pelvis, hip, and knee; kinetics of the hip, knee and ankle; and muscle activation of the gluteus maximus (GM), gluteus medius (GMed), biceps femoris (BF) and vastus lateralis (VL). Differences between groups were calculated using three separate sets of multivariate analysis of variance for kinematics, kinetics, and electromyographic data. Women with PFPS exhibited ipsilateral trunk lean; greater trunk flexion; greater contralateral pelvic drop; greater hip adduction and internal rotation; greater ankle pronation; greater internal hip abductor and ankle supinator moments; lower internal hip, knee and ankle extensor moments; and greater GM, GMed, BL, and VL muscle activity. The results of the present study are related to abnormal movement patterns in women with PFPS. We speculated that these findings constitute strategies to control a deficient dynamic alignment of the trunk and lower limb and to avoid PF pain. However, the greater BF and VL activity and the extensor pattern found for the hip, knee, and ankle of women with PFPS may contribute to increased PF stress.
    PLoS ONE 05/2014; 9(5):e97606. DOI:10.1371/journal.pone.0097606 · 3.53 Impact Factor
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    ABSTRACT: Background Patellofemoral pain is common among runners and is frequently attributed to increased patellofemoral joint stress. The purpose of our study was to examine the effects of changing step length during running on patellofemoral joint stress per step and stress per mile in females with and without patellofemoral pain. Methods Ten female runners with patellofemoral pain and 13 healthy female runners performed running trials at 3.7 m/s in three conditions: preferred step length, at least + 10% step length, and at least -10% step length. Knee flexion angles and internal knee extension moments served as inputs for a biomechanical model to estimate patellofemoral joint stress per step. We also estimated total patellofemoral joint stress per mile based on the number of steps necessary to run a mile during each condition. Findings Patellofemoral joint stress per step increased 31% in the long step length condition (P < .001) and decreased 22.2% in the short step length condition (P < .001). Despite the inverse relationship between step length and number of steps required to run a mile, patellofemoral joint stress per mile increased 14% in the long step length condition (P < .001) and decreased 7.5% in the short step length condition (P < .001). Interpretation These results suggest a direct relationship between step length and patellofemoral joint loads. Total stress per mile experienced at the patellofemoral joint decreased with a short step length despite the greater number of steps necessary to cover this distance. These findings may have relevance with respect to both prevention and treatment of patellofemoral joint pain.
    Clinical biomechanics (Bristol, Avon) 01/2013; DOI:10.1016/j.clinbiomech.2013.12.016 · 1.88 Impact Factor
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    ABSTRACT: Purpose: This study aimed to quantify differences in patellofemoral joint stress which may occur when healthy runners alter their foot strike pattern from their habitual rearfoot strike to a forefoot strike in order to gain insight on the potential etiology and treatment methods of patellofemoral pain. Methods: Sixteen healthy female runners completed twenty running trials in a controlled laboratory setting under rearfoot strike and forefoot strike conditions. Kinetic and kinematic data were used to drive a static optimization technique to estimate individual muscle forces to input into a model of the patellofemoral joint to estimate joint stress during running. Results: Peak patellofemoral joint stress and the stress-time integral over stance phase decreased 27% and 12%, respectively, in the forefoot strike condition (p<0.001). Peak vertical ground reaction force increased slightly in the forefoot strike condition (p<0.001). Peak quadriceps force and average hamstring force decreased while gastrocnemius and soleus muscle forces increased when running with a forefoot strike (p<0.05). Knee flexion angle at initial contact increased (p<0.001), total knee excursion decreased (p<0.001), and no change occurred in peak knee flexion angle (p=0.238). Step length did not change between conditions (p=0.375), but the leading leg landed with the foot positioned with a horizontal distance closer to the hip at initial contact in the forefoot strike condition (p<0.001). Conclusion: Altering one's strike pattern to a forefoot strike results in consistent reductions in patellofemoral joint stress independent of changes in step length. Thus, implementation of forefoot strike training programs may be warranted in the treatment of runners with patellofemoral pain. However, it is suggested that the transition to a forefoot strike pattern be completed in a graduated manner.
    Medicine &amp Science in Sports &amp Exercise 09/2014; DOI:10.1249/MSS.0000000000000503 · 4.46 Impact Factor

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