Tibiofemoral movement 1: the shapes and relative movements of the femur and tibia in the unloaded cadaver knee

Abstract

In six unloaded cadaver knees we used MRI to determine the shapes of the articular surfaces and their relative movements. These were confirmed by dissection.Medially, the femoral condyle in sagittal section is composed of the arcs of two circles and that of the tibia of two angled flats. The anterior facets articulate in extension. At about 20° the femur 'rocks' to articulate through the posterior facets. The medial femoral condyle does not move anteroposteriorly with flexion to 110°.Laterally, the femoral condyle is composed entirely, or almost entirely, of a single circular facet similar in radius and arc to the posterior medial facet. The tibia is roughly flat. The femur tends to roll backwards with flexion.The combination during flexion of no anteroposterior movement medially (i.e., sliding) and backward rolling (combined with sliding) laterally equates to internal rotation of the tibia around a medial axis with flexion. About 5° of this rotation may be obligatory from 0° to 10° flexion; thereafter little rotation occurs to at least 45°. Total rotation at 110° is about 20°, most if not all of which can be suppressed by applying external rotation to the tibia at 90°. The shapes and movements of the femur and tibia as they articulate in the knee have been the subject of anatomical description and debate since 1836. The literature is by now too extensive to review fully. It is cited more completely elsewhere 1 and will be on the JBJS web site (www.jbjs.org. We have examined the non-weight-bearing cadaver knee throughout its range of flexion, extension and longitudinal rotation using MRI. Subsequently, the specimen was dissected in order to confirm our interpretation of the MR images. This investigation offers three advantages compared with dissection alone or radiography. First, the relative positions and shapes of the bones and cartilage in the intact medial and lateral compartments can be established separately but simultaneously at each increment of flexion, a fact crucial to a description of the movement of the knee. Secondly, the menisci and cruciate ligaments can be imaged while the knee is moved with the capsule intact, and thirdly, MRI can be applied without risk to the living knee.In this paper we describe the shapes of the bones in sagittal section and the relative position of the condyles both medially and laterally at certain points in the flexion cycle. It is then possible to deduce the nature of the rotations and translations which occur between the two bones. In principle, this knowledge can be applied to the living knee, as examined by MRI. Materials and MethodsSpecimens were obtained by sectioning the femur and the tibia 15 cm from the joint line without opening the capsule. In total, 24 knees were imaged and dissected to develop the technique described below or to obtain supplemetary information. Six knees were fully imaged for this study. All were from men with a mean age of 43 years (25 to 55). Five were right-sided. None showed abnormalities other than fibrillation of the cartilage.The knee...

Dynamic activity dependence of in vivo normal knee kinematics

“…From 208 to 808 flexion the contact locations moved posterior, inclined 158 to 208 with respect to the tibia, maintaining the femur approximately in line with the foot as previously reported. 11 However, unlike previous reports, contact-derived rotation continued from 808 to full flexion in squat and kneel. From 808 to maximum flexion, the contact-derived and rigid body bone rotations showed similar curves, which is reasonable considering the circular geometry of the posterior femoral condyles.…”

“…Significant differences in early flexion (08 to 308) are due to femoral geometry. Iwaki et al 11 showed that the sagittal profile of the medial femoral condyle is composed of a larger distal and smaller posterior circular arc, while the lateral condyle is well described by a single circular facet. From extension to mid flexion, the medial tibial contact area had a more ovoid shape and moved posteriorly (Figs.…”

In Vivo Kinematics after a Cruciate-substituting TKA

“…This is supported with findings from fluoroscopy, studies using in vitro analyses, and those using external markers associated with gait laboratory systems [1, 2, 4, 8-10, 12, 13, 16, 18, 19, 21, 22, 24, 25, 34-37]. With increasing knee flexion, the normal knee reportedly experiences more posterior motion of the lateral condyle leading to internal rotation of the tibia with respect to the femur [18,22,25]. In contrast to the normal knee, in vivo kinematic analyses suggest subjects undergoing TKA often experience a motion pattern opposite the normal knee where the condyles slide in the anterior direction with increasing knee flexion [2,8,9,24,28,31,[34][35][36][37].…”

Analysis of tibial rotation using magnetic resonance imaging

“…Although morphological studies on the shape and congruence of the tibia and femur have been conducted (Iwaki et al, 2000), the nature of tibial rotation in normal subjects is not well understood, with many researchers having used measurements obtained at close to terminal extension to see if the tibia rotates externally with knee extension, an effect known as screw-home motion (Hallen & Lindahl, 1966;Todo et al, 1999;Iwaki et al, 2000;Piazza & …”

“…Although several studies have been conducted to determine tibial displacement on the femur at different knee angles of flexion (Iwaki et al, 2000;Logan et al, 2004), the degree of in vivo tibial rotation at different angles remains relatively undetermined.…”