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: 2.99). 02/2012; 30(2):209-13. DOI: 10.1002/jor.21523
Source: PubMed


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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    • "Several numerical and in vitro studies showed that reduction of patellar thickness can lead to increase of patellar bone strain (Amirouche et al., 2013; Fitzpatrick et al., 2013; Lie et al., 2005), thus increasing risk of the patellar fracture and possibly contributing to AKP symptoms (Draper et al., 2012; Ho et al., 2014). However, these studies were conducted on cadaveric knees. "
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    • "Depending on factors such as running speed, foot strike pattern and step length, the PFJ experiences peak contact forces between 4-10 body weights (Kernozek et al., 2015; Lenhart et al., 2014; Willson et al., 2015). The repetitive application of elevated forces to the patellar articular cartilage at a high rate of loading is thought to contribute to PFP by increasing patellar interosseous pressure and subchondral bone metabolic activity (Draper et al., 2012; Ho et al., 2013). Altered lower extremity mechanics such as increased hip adduction excursion (Barton et al., 2009) and increased hip and knee abduction angular impulse (Stefanyshyn et al., 2006; Willson and Davis, 2009) have also been observed among runners with PFP and hypothesized to contribute to the etiology or exacerbation of PFJ symptoms. "
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    • "It has been reported that individuals with PFP exhibit greater patellofemoral joint stress during weight-bearing activities when compared to painfree controls (Farrokhi, Keyak, & Powers, 2011; Heino Brechter & Powers, 2002). Chronic overloading of the patellofemoral joint is thought to result in pathological changes in the subchondral bone, including bone microfracture (Imhof, Breitenseher , Kainberger, Rand, & Trattnig, 1999; Radin & Rose, 1986), increased subchondral bone metabolic activity (Draper et al., 2011; Dye, 2005; Naslund, Odenbring, Naslund, & Lundeberg, 2005), and elevated bone water content (Li et al., 2008). "
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