In‐vivo patellar tendon kinematics during weight‐bearing deep knee flexion

This study quantified in‐vivo 3D patellar tendon kinematics during weight‐bearing deep knee bend beyond 150°. Each knee was MRI scanned to create 3D bony models of the patella, tibia, femur, and the attachment sites of the patellar tendon on the distal patella and the tibial tubercle. Each attachment site was divided into lateral, central, and medial thirds. The subjects were then imaged using a dual fluoroscopic image system while performing a deep knee bend. The knee positions were determined using the bony models and the fluoroscopic images. The patellar tendon kinematics was analyzed using the relative positions of its patellar and tibial attachment sites. The relative elongations of all three portions of the patellar tendon increased similarly up to 60°. Beyond 60°, the relative elongation of the medial portion of the patellar tendon decreased as the knee flexed from 60° to 150° while those of the lateral and central portions showed continuous increases from 120° to 150°. At 150°, the relative elongation of the medial portion was significantly lower than that of the central portion. In four of seven knees, the patellar tendon impinged on the tibial bony surface at 120° and 150° of knee flexion. These data may provide useful insight into the intrinsic patellar tendon biomechanics during a weight‐bearing deep knee bend and could provide biomechanical guidelines for future development of total knee arthroplasties that are intended to restore normal knee function. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1596–1603, 2012     

Dynamic activity dependence of in vivo normal knee kinematics

Dynamic knee kinematics were analyzed for normal knees in three activities, including two different types of maximum knee flexion. Continuous X‐ray images of kneel, squat, and stair climb motions were taken using a large flat panel detector. CT‐derived bone models were used for model registration‐based 3D kinematic measurement. Three‐dimensional joint kinematics and contact locations were determined using three methods: bone‐fixed coordinate systems, interrogation of CT‐based bone model surfaces, and interrogation of MR‐based articular cartilage model surfaces. The femur exhibited gradual external rotation throughout the flexion range. Tibiofemoral contact exhibited external rotation, with contact locations translating posterior while maintaining 15° to 20° external rotation from 20° to 80° of flexion. From 80° to maximum flexion, contact locations showed a medial pivot pattern. Kinematics based on bone‐fixed coordinate systems differed from kinematics based on interrogation of CT and MR surfaces. Knee kinematics varied significantly by activity, especially in deep flexion. No posterior subluxation occurred for either femoral condyle in maximum knee flexion. Normal knees accommodate a range of motions during various activities while maintaining geometric joint congruency. © Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:428–434, 2008     

Analysis of the kinematics of total knee prostheses with a medial pivot design

Analysis of the kinematics of the FINE Total Knee System (Nakashima Medical, Okayama, Japan) revealed that the medial condyle is fixed and the lateral condyle shows lateral posterior movement and tibial internal rotation. Analysis of the kinematics of the ADVANCE Total Knee System (Wright Medical Technology, Arlington, Tenn) revealed that the medial condyle is fixed and the lateral condyle shows anterior movement in the early stage, changing thereafter to posterior movement. With regard to rotation, initial external rotation subsequently changes to internal rotation. Analysis of the kinematics of the ADVANTIM Total Knee System (Wright Medical Technology) revealed that the bicondyle shows posterior movement, subsequently changing to anterior and posterior movements. Thus, unlike the FINE or ADVANCE Total Knee Systems, the ADVANTIM Total Knee System shows internal rotation.     

Differences in patellofemoral kinematics between weight‐bearing and non‐weight‐bearing conditions in patients with patellofemoral pain

Patellar maltracking is thought to be one source of patellofemoral pain. Measurements of patellar tracking are frequently obtained during non‐weight‐bearing knee extension; however, pain typically arises during highly loaded activities, such as squatting, stair climbing, and running. It is unclear whether patellofemoral joint kinematics during lightly loaded tasks replicate patellofemoral joint motion during weight‐bearing activities. The purpose of this study was to: evaluate differences between upright, weight‐bearing and supine, non‐weight‐bearing joint kinematics in patients with patellofemoral pain; and evaluate whether the kinematics in subjects with maltracking respond differently to weight‐bearing than those in nonmaltrackers. We used real‐time magnetic resonance imaging to visualize the patellofemoral joint during dynamic knee extension from 30° to 0° of knee flexion during two conditions: upright, weight‐bearing and supine, non‐weight‐bearing. We compared patellofemoral kinematics measured from the images. The patella translated more laterally during the supine task compared to the weight‐bearing task for knee flexion angles between 0° and 5° (p = 0.001). The kinematics of the maltrackers responded differently to joint loading than those of the non‐maltrackers. In subjects with excessive lateral patellar translation, the patella translated more laterally during upright, weight‐bearing knee extension for knee flexion angles between 25° and 30° (p = 0.001). However, in subjects with normal patellar translation, the patella translated more laterally during supine, non‐weight‐bearing knee extension near full extension (p = 0.001). These results suggest that patellofemoral kinematics measured during supine, unloaded tasks do not accurately represent the joint motion during weight‐bearing activities. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:312–317, 2011     

Sex differences in coupled knee motions during the transition from non-weight bearing to weight bearing

Knee ligament injuries frequently happen when the joint transitions from non-weight bearing (NWB) to weight bearing (WB). To gain insight into the mechanism that produces these injuries, physically active females (N = 41) and males (N = 39) underwent measurement of coupled tibiofemoral joint displacements [anterior tibial translation (ATT) and varus–valgus and internal–external rotations] and neuromuscular responses as the knee transitioned from NWB to WB in response to a 40% body weight load applied under the control of gravity. The transition from NWB to WB produced no difference in ATT between males and females; however, significant sex-based differences were noted for both transverse and frontal plane knee motions. With the knee NWB, females were in a greater absolute valgus compared to males (6.6 vs. 5.0°), and moved through greater varus motion than males during the transition from NW to WB (2.3 vs. 1.4°), resulting in similar valgus alignment for both sexes at peak WB (4.3 vs. 3.6°). In the transverse plane, the knees of females were positioned in more external rotation compared to males when NWB (1.4 vs. −0.3°), then females externally rotated their knees while males internally rotated their knees during the transition from NWB to WB. This resulted in a 3.4° difference in transverse plane knee position at peak WB (2.3 vs. −1.1°). Our findings suggest that the coupled knee motions produced during the transition from NWB to WB are sex dependent, and may provide insight into the knee motion patterns that place females at increased risk of knee ligament injury. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 717–723, 2009     

In‐vivo three‐dimensional knee kinematics during daily activities in dogs

The canine knee is morphologically similar to the human knee and thus dogs have been used in experimental models to study human knee pathology. To date, there is limited data of normal canine 3D knee kinematics during daily activities. The objective of this study was to characterize 3D in‐vivo femorotibial kinematics in normal dogs during commonly performed daily activities. Using single‐plane fluoroscopy, six normal dogs were imaged performing walk, trot, sit, and stair ascent activities. CT‐generated bone models were used for kinematic measurement using a 3D‐to‐2D model registration technique. Increasing knee flexion angle was typically associated with increasing tibial internal rotation, abduction and anterior translation during all four activities. The precise relationship between flexion angle and these movements varied both within and between activities. Significant differences in axial rotation and coronal angulation were found at the same flexion angle during different phases of the walk and trot. This was also found with anterior tibial translation during the trot only. Normal canine knees accommodate motion in all planes; precise kinematics within this envelope of motion are activity dependent. This data establishes the characteristics of normal 3D femorotibial joint kinematics in dogs that can be used as a comparison for future studies. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1603–1610, 2015.     

Localization of the full‐thickness cartilage lesions in medial and lateral unicompartmental knee osteoarthritis

This study's aim was to determine the patterns of osteoarthritis (OA) in both unicompartmental medial and lateral OA of the knee. Forty patients with medial and 20 with lateral unicompartmental knee osteoarthritis were studied to determine the location of full‐thickness cartilage lesions. Intraoperatively, the distance between margins of the lesion and reference lines were measured. The femoral measurements were transposed onto lateral radiographs to determine the relationship between the lesion site and knee flexion angles. Both tibial and femoral lesions were significantly (p < 0.01) more posterior in lateral OA than medial OA. In medial OA, the lesion center was, on average, at 11° (SD 3°) of flexion, whereas in lateral OA, it was at 40° (SD 3°). The smallest medial femoral lesions were near full extension and, as they enlarged, they extended posteriorly. The smallest lateral femoral lesions extended from 20° to 60° flexion. As these lesions enlarged, they extended both anteriorly and posteriorly. There was a well‐defined relationship between the site of the lesions and their size, suggesting that they develop and progress in a predictable manner. The relationship was different for medial and lateral OA, suggesting that different mechanical factors are important in initiating the different types of OA. The lesions in medial OA occur in extension, perhaps initiated by events occurring at heel strike. The lesions in lateral OA begin at flexion angles above those occurring during the single leg stance phase of the gait cycle, so activities other than gait are likely to induce lateral OA. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1339–1346, 2009     

Three‐dimensional patellar motion at the natural knee during passive flexion/extension. An in vitro study

Patellar maltracking may result in many patellofemoral joint (PFJ) disorders in the natural and replaced knee. The literature providing quantitative reference for normal PFJ kinematics according to which patellar maltracking could be identified is still limited. The aim of this study was to measure in vitro accurately all six‐degrees‐of‐freedom of patellar motion with respect to the femur and tibia on 20 normal specimens. A state‐of‐the‐art knee navigation system, suitably adapted for this study aim, was used. Anatomical reference frames were defined for the femur, tibia, and patella according to international recommendations. PFJ flexion, tilt, rotation, and translations were calculated in addition to standard tibiofemoral joint (TFJ) kinematics. All motion patterns were found to be generally repeatable intra‐/interspecimens. PFJ flexion was 62% of the corresponding TFJ flexion range; tilt and translations along femoral mediolateral and tibial proximodistal axes during TFJ flexion were found with medial, lateral, and distal trends and within 12°, 6 and 9 mm, respectively. No clear pattern for PFJ rotation was observed. These results concur with comparable reports from the literature and contribute to the controversial knowledge on normal PFJ kinematics. Their consistence provides fundamental information to understand orthopedic treatment of the knee and for possible relevant measurements intraoperatively. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1426–1431, 2009     

Kinematics of medial osteoarthritic knees before and after posterior cruciate ligament retaining total knee arthroplasty

Total knee arthroplasty (TKA) is a widely accepted surgical procedure for the treatment of patients with end‐stage osteoarthritis (OA). However, the function of the knee is not always fully recovered after TKA. We used a dual fluoroscopic imaging system to evaluate the in vivo kinematics of the knee with medial compartment OA before and after a posterior cruciate ligament‐retaining TKA (PCR‐TKA) during weight‐bearing knee flexion, and compared the results to those of normal knees. The OA knees displayed similar internal/external tibial rotation to normal knees. However, the OA knees had less overall posterior femoral translation relative to the tibia between 0° and 105° flexion and more varus knee rotation between 0° and 45° flexion, than in the normal knees. Additionally, in the OA knees the femur was located more medially than in the normal knees, particularly between 30° and 60° flexion. After PCR‐TKA, the knee kinematics were not restored to normal. The overall internal tibial rotation and posterior femoral translation between 0° and 105° knee flexion were dramatically reduced. Additionally, PCR‐TKA introduced an abnormal anterior femoral translation during early knee flexion, and the femur was located lateral to the tibia throughout weight‐bearing flexion. The data help understand the biomechanical functions of the knee with medial compartment OA before and after contemporary PCR‐TKA. They may also be useful for improvement of future prostheses designs and surgical techniques in treatment of knees with end‐stage OA. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:40–46, 2011     

Sectioning the medial patellofemoral ligament alters patellofemoral joint kinematics and contact mechanics

Medial patellofemoral ligament (MPFL) disruption may alter patellofemoral joint (PFJ) kinematics and contact mechanics, potentially causing pain and joint degeneration. In this controlled laboratory study, we investigated the hypothesis that MPFL transection would change patellar tracking and PFJ contact pressures and increase the distance between the attachment points of the MPFL. Eight fresh frozen dissected cadaveric knees were mounted in a rig with the quadriceps and ITB loaded to 205 N. An optical tracking system measured joint kinematics, and pressure sensitive film between the patella and trochlea measured PFJ contact pressures. Length patterns of the distance between the femoral and patellar attachments of the MPFL were measured using a suture led to a linear displacement transducer. Measurements were repeated with the MPFL intact and following MPFL transection. A significant increase in the distance between the patellar and femoral MPFL attachment points was noted following transection (p < 0.05). MPFL transection resulted in significantly increased lateral translation and lateral tilt of the patella in early flexion (p < 0.05). Peak and mean medial PFJ contact pressures were significantly reduced and peak lateral contact pressures significantly elevated in early knee flexion following MPFL transection (p < 0.05). MPFL transection resulted in significant alterations to PFJ tracking and contact pressures, which may affect articular cartilage health. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1423–1429, 2013     

Fixed‐bearing medial unicompartmental knee arthroplasty restores neither the medial pivoting behavior nor the ligament forces of the intact knee in passive flexion

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non‐conforming, fixed bearing medial UKA affects tibiofemoral kinematics, and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior–posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° of flexion, but occurred from 30° to 90° of flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non‐conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1868–1875, 2018.

     

Comparison of posterior-stabilized,cruciate-retaining,and medial-stabilized knee implant motion during gait

Accurate knowledge of knee joint motion is needed to evaluate the effects of implant design on functional performance and component wear. We conducted a randomized controlled trial to measure and compare 6-degree-of-freedom (6-DOF) kinematics and femoral condylar motion of posterior-stabilized (PS), cruciate-retaining (CR), and medial-stabilized (MS) knee implant designs for one cycle of walking. A mobile biplane X-ray imaging system was used to accurately measure 6-DOF tibiofemoral motion as patients implanted with PS (n = 23), CR (n = 25), or MS (n = 26) knees walked over ground at their self-selected speeds. Knee flexion angle did not differ significantly between the three designs. Relative movements of the femoral and tibial components were generally similar for PS and CR with significant differences observed only for anterior tibial drawer. Knee kinematic profiles measured for MS were appreciably different: external rotation and abduction of the tibia were increased while peak-to-peak anterior drawer was significantly reduced for MS compared with PS and CR. Anterior-posterior drawer and medial-lateral shift of the tibia were strongly coupled to internal-external rotation for MS, as was anterior-posterior translation of the contact center in the lateral compartment. MS exhibited the least amount of paradoxical anterior translation of the femur relative to the tibia during knee flexion. The joint center of rotation in the transverse plane was located in the lateral compartment for PS and CR and in the medial compartment for MS. Substantial differences were evident in 6-DOF knee kinematics between the healthy knee and all three prosthetic designs. Overall, knee kinematic profiles observed for MS resemble those of the healthy joint more closely than PS and CR.     

In vivo kinematics of the thumb during flexion and adduction motion: Evidence for a screw‐home mechanism

The thumb plays a crucial role in basic hand function. However, the kinematics of its entire articular chain have not yet been quantified. Such investigation is essential to improve our understanding of thumb function and to develop better strategies to treat thumb joint pathologies. The primary objective of this study is to quantify the in vivo kinematics of the trapeziometacarpal (TMC) and scaphotrapezial (ST) joints during flexion and adduction of the thumb. In addition, we want to evaluate the potential coupling between the TMC and ST joints during these tasks. The hand of 16 asymptomatic women without signs of thumb osteoarthritis were CT scanned in positions of maximal thumb extension, flexion, abduction, and adduction. The CT images were segmented and three‐dimensional surface models of the radius, scaphoid, trapezium, and the first metacarpal were created for each thumb motion. The corresponding rotations angles, translations, and helical axes were calculated for each sequence. The analysis shows that flexion and adduction of the thumb result in a three‐dimensional rotation and translation of the entire articular chain, including the trapezium and scaphoid. A wider range of motion is observed for the first metacarpal, which displays a clear axial rotation. The coupling of axial rotation of the first metacarpal with flexion and abduction during thumb flexion supports the existence of a screw‐home mechanism in the TMC joint. In addition, our results point to a potential motion coupling between the TMC and ST joints and underline the complexity of thumb kinematics. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1556–1564, 2017.

     

Oxford medial unicompartmental knees display contact‐loss during step‐cycle motion and bicycle motion: A dynamic radiostereometric study

The Oxford medial unicompartmental knee is designed fully congruent, with the purpose of maintaining a large contact‐area throughout motion and minimize wear. No other study has investigated this design feature in‐vivo. We aimed to evaluate if contact‐loss was introduced between the articulating surfaces of the Oxford medial unicompartmental knee during bicycle‐ and step‐cycle motion, and whether this correlated with essential implant parameters, such as polyethylene (PE) wear, knee‐loadings, and clinical outcome. To study contact‐loss, 15 patients (12 males, mean age 69 years) with an Oxford medial unicompartmental knee (7 cemented, mean follow‐up 4.4 years) were examined with use of dynamic radiostereometry (RSA) (10 frames/s). PE wear was measured from static RSA and clinical outcome was evaluated with American Knee Society Score (AKSS) and Oxford Knee Score (OKS). Data on knee‐loadings were acquired from the literature. Contact‐loss was deteced in all patients during both exercises, and the trend of contact‐loss correlated with the knee‐loadings. Median contact‐loss was 0.8 mm (95%PI: 0.3; 1.5) for bicycle motion and 0.3 mm (95%PI: 0.24; 0.35) for step‐cycle motion, and did not correlate with the PE wear rate of mean 0.06 mm/year. Possible in‐congruency was seen in three patients. Clinical outcome scores correlated with contact‐loss during step‐cycle motion. In conclusion, contact‐loss was seen in all patients indicating a clinical tolerance during load. Contact‐loss followed the knee‐loadings, which could explain why no correlation was seen with PE wear, as an increase in load was acommadated by an increase in contact‐area (contact‐loss reduction). The size of contact‐loss may reflect clinical outcome. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:357–364, 2018.     

Understanding patellofemoral pain with maltracking in the presence of joint laxity: Complete 3D in vivo patellofemoral and tibiofemoral kinematics

Patellofemoral pain is widely accepted as one of the most common pathologies involving the knee, yet the etiology of this pain is still an open debate. Generalized joint laxity has been associated with patellofemoral pain, but is not often discussed as a potential source of patellar maltracking. Thus, the objective of this study was to compare the complete 6 degree of freedom patellofemoral and tibiofemoral kinematics from a group of patients diagnosed with patellofemoral pain syndrome and maltracking to those from an asymptomatic population. The following null hypotheses were tested: kinematic alterations in patellofemoral maltracking are limited to the axial plane; knee joint kinematics are the same in maltrackers with and without generalized joint laxity (defined by a clinical diagnosis of Ehlers Danlos Syndrome); and no correlations exist between tibiofemoral and patellofemoral kinematics or within patellofemoral kinematics. This study demonstrated that alterations in patellofemoral kinematics, associated with patellofemoral pain, are not limited to the axial plane, minimal correlations exist between patellofemoral and tibiofemoral kinematics, and distinct subgroups likely exist within the general population of maltrackers. Being able to identify subgroups correctly within the omnibus diagnosis of patellar maltracking is a crucial step in correctly defining the pathophysiology and the eventual treatment of these patients. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 561–570, 2009     

The pattern of cartilage damage in antero‐medial osteoarthritis of the knee and its relationship to the anterior cruciate ligament

Within antero‐medial gonarthrosis (AMG) of the knee, there is a spectrum of damage seen in the functionally intact anterior cruciate ligament (ACL). Our aim was to correlate the degree of ACL damage to the geographical extent and degree of cartilage loss on the tibial plateau. Ninety tibial plateaus resected during unicompartmental arthroplasty were photographed and digitally mapped. The ACL damage was graded (0: normal, 1: synovium loss, 2: longitudinal splits), and dimensions of full thickness cartilage loss and damage recorded. The percentage of full thickness loss in patients with a normal ACL was compared to those with a damaged, but functionally intact ligament. All specimens showed similar elliptical loss of cartilage in the antero‐medial part of the tibial plateau. A total of 45(50%) patients had a macroscopically normal ACL, 21(23%) had synovial loss, and 24(27%) had longitudinal splits. An increase in the area of cartilage damage was seen with progressive ACL damage (p < 0.001). The area of macroscopically normal cartilage found posteriorly did not change. This study demonstrates that phenotypic distribution of cartilage damage in AMG is highly reproducible with a pattern of increasing cartilage erosion associated with increasing ACL damage. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 908–913, 2013     

Six DOF in vivo kinematics of the ankle joint complex: Application of a combined dual‐orthogonal fluoroscopic and magnetic resonance imaging technique

Accurate knowledge of in vivo ankle joint complex (AJC) biomechanics is critical for understanding AJC disease states and for improvement of surgical treatments. This study investigated 6 degrees‐of‐freedom (DOF) in vivo kinematics of the human AJC using a combined dual‐orthogonal fluoroscopic and magnetic resonance imaging (MRI) technique. Five healthy ankles of living subjects were studied during three in vivo activities of the foot, including maximum plantarflexion and dorsiflexion, maximum supination and pronation, and three weight‐bearing positions in simulated stance phases of walking. A three‐dimensional (3D) computer model of the AJC (including tibia, fibula, talus, and calcaneus) was constructed using 3D MR images of the foot. The in vivo AJC position at each selected position of the foot was captured using two orthogonally positioned fluoroscopes. In vivo AJC motion could then be reproduced by coupling the orthogonal images with the 3D AJC model in a virtual dual‐orthogonal fluoroscopic system. From maximum dorsiflexion to plantarflexion, the arc of motion of the talocrural joint (47.5 ± 2.2°) was significantly larger than that of the subtalar joint (3.1 ± 6.8°). Both joints showed similar degrees of internal–external and inversion–eversion rotation. From maximum supination to pronation, all rotations and translations of the subtalar joint were significantly larger than those of the talocrural joint. From heel strike to midstance, the plantarflexion contribution from the talocrural joint (9.1 ± 5.3°) was significantly larger than that of the subtalar joint (?0.9 ± 1.2°). From midstance to toe off, internal rotation and inversion of the subtalar joint (12.3 ± 8.3° and ?10.7 ± 3.8°, respectively) were significantly larger than those of the talocrural joint (?1.6 ± 5.9° and ?1.7 ± 2.7°). Strong kinematic coupling between the talocrural and subtalar joints was observed during in vivo AJC activities. The contribution of the talocrural joint to active dorsi‐plantarflexion was higher than that of the subtalar joint, whereas the contribution of the subtalar joint to active supination–pronation was higher than that of the talocrural joint. In addition, the talocrural joint demonstrated larger motion during the early part of stance phase while the subtalar joint contributes more motion during the later part of stance phase. The results add quantitative data to an in vivo database of normals that can be used in clinical diagnosis, treatment, and evaluation of the AJC after injuries. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res