Knee joint kinematics during walking influences the spatial cartilage thickness distribution in the knee
Introduction
The factors influencing the phenotypic thickness variation in the articular cartilage at the knee is an important consideration in understanding pathomechanics of degenerative disease such as osteoarthritis. It has been suggested that the joint loading conditions during normal activities can affect knee articular cartilage morphology (Andriacchi et al., 2004a, Jones et al., 2000). While it has been reported that loading during activities such as walking influence the medial–lateral variations in bone density (Hurwitz et al., 1998) and cartilage thickness (Miyazaki et al., 2002), the kinematic factors that affect variations in cartilage thickness are still not well understood. Yet, the regional sensitivity of cartilage morphology is important, since it has been suggested that the kinematic changes at the knee can lead to osteoarthritis (Andriacchi et al., 2009).
The mechanics of walking offer the opportunity to test the relationship between gait mechanics and cartilage, since patterns of movement and loading are repeatable (Kadaba et al., 1989). For example, axial knee joint loading for normal walking has three peak amplitudes during the stance phase of gait (Schipplein and Andriacchi, 1991) with a large force at heel strike. It has also been shown (Koo and Andriacchi, 2008) that the anterior–posterior (AP) position of contact on the medial and lateral compartment of the knee changes during the heel strike phase of walking and can be related to a unique combination of knee flexion, AP position and internal–external (IE) rotation.
The loading and kinematic conditions that occur at heel strike during walking offer a unique opportunity to test for a relationship between regional cartilage thickness and individual variation in the kinematics of the knee during walking. Specifically, it would be important to know if healthy cartilage is adapted to normal kinematics during walking, since it has been suggested that kinematic changes associated with conditions such as ACL injury can lead to a degenerative pathway for cartilage (Chaudhari et al., 2008, Lohmander et al., 2004) by shifting loads to regions of cartilage that are not conditioned to sustain the chronic loads associated with the mechanics of walking (Andriacchi et al., 2009).
The observations described above suggest that if knee kinematics influence variations in cartilage thickness then there would be correlations between the knee kinematics during heel strike of walking and cartilage thickness.
The purpose of this study was to test the hypothesis that the AP spatial cartilage thickness distributions in the medial and lateral compartments of the distal femur and proximal tibia are influenced by the knee flexion angle (primary motion of the knee) as shown in Fig. 1 and the AP translation and internal–external (IE) rotation (secondary motions of the knee) that occur at heel strike during walking.
Section snippets
Participants
Seventeen healthy volunteers (10 males and 7 females) without history of significant knee injuries enrolled in the study. Average (±One Standard Deviation) age was 33.2±9.8 years old and average BMI was 23.0±2.4 kg/m2. The study was approved by the IRB at Stanford University (California, USA) and an informed consent was obtained from each volunteer prior to testing. Each volunteer underwent knee magnetic resonance imaging (MRI) and gait testing as explained below.
MR imaging and 3D modeling of knee cartilage
High contrast MR images
Femoral cartilage thickness
The average FE angle at heel strike for the left knee of 17 volunteers was −2.1±3.3° (hyperextension); 25th and 75th percentiles were −4.8° and 0.3°, respectively.
Angular locations of the thickest cartilage on the femoral cartilage were identified in both medial and lateral condyles. The locations of the thickest cartilage in the medial condyles were significantly correlated (R2=0.41, p<0.01) with the knee FE angle at heel strike, while the locations in the lateral condyles were not associated
Discussion
The results suggest that the cartilage thickness distribution of the distal femoral cartilage was influenced by the knee flexion angle during walking only in the medial compartment. The medial and lateral compartments in the knee have different contact situations according to the shape of the contacting surfaces (Koo and Andriacchi, 2007). The tibiofemoral contact surfaces in the medial compartment are more conforming (convex–concave), so the contact location is sensitive to small differences
Conflict of interest statement
None
Acknowledgements
This study was funded by NIH R01 AR049792 and Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology (2010-0001645).
References (25)
Optimal circular fit to objects in 2 and 3 dimensions
Pattern Recognition Letters
(1990)- et al.
Obesity is not associated with increased knee joint torque and power during level walking
Journal of Biomechanics
(2003) - et al.
Dynamic knee loads during gait predict proximal tibial bone distribution
Journal of Biomechanics
(1998) - et al.
Considerations in measuring cartilage thickness using MRI: Factors influencing reproducibility and accuracy
Osteoarthritis and Cartilage
(2005) - et al.
A comparison of the influence of global functional loads vs. local contact anatomy on articular cartilage thickness at the knee
Journal of Biomechanics
(2007) - et al.
The knee joint center of rotation is predominantly on the lateral side during normal walking
Journal of Biomechanics
(2008) - et al.
The cartilage thickness distribution in the tibiofemoral joint and its correlation with cartilage-to-cartilage contact
Clinical Biomechanics
(2005) - et al.
A point cluster method for in vivo motion analysis: applied to a study of knee kinematics
Journal of Biomechanical Engineering
(1998) - et al.
A framework for the in vivo pathomechanics of osteoarthritis at the knee
Annals of Biomedical Engineering
(2004) - et al.
Musculoskeletal dynamics locomotion, and clinical applications