Subject: Thorp,LE

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Latest Paper:

Arthritis Rheum. 2007 Sep 28;57 (7):1254-1260 17907211 (P,S,E,B,D)

Relationship between pain and medial knee joint loading in mild radiographic knee osteoarthritis.

Laura E Thorp, Dale R Sumner, Markus A Wimmer, Joel A Block

OBJECTIVE: The relationship between knee pain and radiographic evidence of knee osteoarthritis (OA) is notoriously imperfect. In particular, conditions that distinguish individuals with symptoms from those with comparable radiographic involvement who remain asymptomatic are unclear. We investigated dynamic loading across the knee in individuals with mild radiographic OA who were distinguished by the presence or absence of knee pain. METHODS: Subjects were recruited into 3 groups: symptomatic with a Kellgren/Lawrence (K/L) grade of 2 (n = 52), asymptomatic with a K/L grade of 2 (n = 19), and asymptomatic with a K/L grade of 0 or 1 (n = 37), the latter representing a normal comparator group. Dynamic knee loading was assessed with gait analysis, and both the peak external knee adduction moment and the knee adduction angular impulse were determined. RESULTS: Peak knee adduction moment and knee adduction angular impulse were 19% and 30% higher, respectively, in symptomatic K/L grade 2 individuals than in asymptomatic individuals with the same radiographic grade (P < 0.05). Conversely, the asymptomatic K/L grade 2 group did not differ from the K/L grade 0-1 normal comparator group (P = 1.00). CONCLUSION: Among individuals with mild radiographic knee OA (K/L grade 2), those who are symptomatic have significantly higher medial compartment loads than those who are asymptomatic, whereas those who are asymptomatic do not differ from normal controls (asymptomatic K/L grade 0 or 1). These findings suggest a biomechanical component to the distinction between asymptomatic and symptomatic radiographic OA, which may be pathophysiologically important.

Arthritis Rheum. 2006 Nov 28;54 (12):3842-3849 17133592 (P,S,E,B,D)

Knee joint loading differs in individuals with mild compared with moderate medial knee osteoarthritis.

Laura E Thorp, D Richman Sumner, Joel A Block, Kirsten C Moisio, Susan Shott, Markus A Wimmer

Rush University Medical Center, Chicago, Illinois.

OBJECTIVE: To compare the knee joint loading patterns in individuals with differing radiographic grades of knee osteoarthritis (OA) for characterization of the mechanical implications of different structural states, and to compare the knee adduction angular impulse, a measure of gait complementary to the commonly used peak knee adduction moment. METHODS: Asymptomatic subjects (those without knee OA) having a Kellgren/Lawrence (K/L) radiographic severity grade of 0 or 1 (n = 28) and subjects with symptomatic knee OA having K/L grades of 2 (n = 66) or 3 (n = 23) were recruited. Gait analysis was used to calculate the peak external knee adduction moment and the external knee adduction angular impulse for the whole stance and for the 4 subdivisions of stance. RESULTS: Both the peak knee adduction moment and the knee adduction angular impulse increased with K/L radiographic grade (P < 0.05). However, only the knee adduction angular impulse differed between subjects with moderate (grade 3) and those with mild (grade 2) radiographic knee OA (P < 0.05). CONCLUSION: The differences between mild and moderate symptomatic radiographic knee OA are not only structural but also functional, based on the magnitude of load in the medial knee joint. Moreover, knee adduction angular impulse provides additional information beyond that available from the peak knee adduction moment, and may therefore be an important gait parameter to include in OA research. These findings are important for our understanding of the pathophysiologic mechanisms of OA.

Bone. 2006 Jun 15; : 16782419 (P,S,E,B)

Bone mineral density in the proximal tibia varies as a function of static alignment and knee adduction angular momentum in individuals with medial knee osteoarthritis.

L E Thorp, M A Wimmer, J A Block, K C Moisio, S Shott, B Goker, D R Sumner

Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, IL 60612, USA.

Based on the premise that bone mass and bone geometry are related to load history and that subchondral bone may play a role in osteoarthritis (OA), we sought to determine if static and dynamic markers of knee joint loads explain variance in the medial-to-lateral ratio of proximal tibial bone mineral density (BMD) in subjects with mild and moderate medial knee OA. We utilized two surrogate markers of dynamic load, the peak knee adduction moment and the knee adduction angular momentum, the latter being the time integral of the frontal plane knee joint moment. BMD for medial and lateral regions of the proximal tibial plateau and one distal region in the tibial shaft was measured in 84 symptomatic subjects with Kellgren and Lawrence radiographic OA grades of 2 or 3. Utilizing gait analysis, the peak knee adduction moment (the external adduction moment of greatest magnitude) and the time integral of the frontal plane knee joint moment (the angular momentum) over the entire stance phase as well as for each of the four subdivisions of stance were calculated. The BMD ratio was not significantly different in grade 2 (1.32 +/- 0.27) and grade 3 knees (1.47 +/- 0.40) (P = 0.215). BMD of the tibial shaft was not correlated with any loading parameter or static alignment. Of all the surrogate gait markers of dynamic load, the knee adduction angular momentum in terminal stance explained the most variance (20%) in the medial-to-lateral BMD ratio (adjusted r(2) = 0.196, P < 0.001). The knee adduction angular momentum for the entire stance phase explained 18% of the variance in the BMD ratio (adjusted r(2) = 0.178, P < 0.001), 10% more variance than explained by the overall peak knee adduction moment (adjusted r(2) = 0.081, P < 0.001). 18% of the variance in the BMD ratio was also explained by the knee alignment angle (adjusted r(2) = 0.183, P < 0.001), and the total explanatory power was increased to 22% when the knee adduction angular momentum in terminal stance was added (change in r(2) = 0.041, P < 0.05, total adjusted r(2) = 0.215, P < 0.001). The BMD ratio and its relationship to dynamic and static markers of loading were independent of height, weight, and the body mass index, demonstrating that both dynamic markers of knee loading as well as knee alignment explained variance in the tibial BMD ratio independent of body size.

by BioInfoBank Institute

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