Development of the concepts of knee kinematics1 Paul N Smith, BMBS, Kathryn M Refshauge, PhD, Jennifer M Scarvell, BAppSc  Archives of Physical Medicine and Rehabilitation  Volume 84, Issue 12, Pages 1895-1902 (December 2003) DOI: 10.1016/S0003-9993(03)00281-8

Fig 1 Anatomically sagittal diagram of the medial and lateral femoral condyles. The axis of knee flexion and extension or “instant center” moves as the knee flexes, following a predictable pathway. Here the instant center pathway is shown for the tibiofemoral joint and the patellofemoral joint for the medial and lateral femoral condyles. The distance from the instant center to the joint surface is the radius of curvature, which appears to vary throughout knee flexion.5 NOTE. The radius of curvature m to m′ ranges from 17 to 38mm for the medial femoral condyle; the radius of curvature n to n′ ranges from 12 to 60mm for the lateral femoral condyle. Legend: m to m′, instant center pathway for tibiofemoral joint; m′ to m”, instant center pathway for patellofemoral joint; t, anterior limit of tibiofemoral contact; n to n′, instant center pathway for tibiofemoral joint; n′ to n”, instant center pathway for the patellofemoral joint. Reprinted with permission.5 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 2 Diagram of the axial view of the right distal femur as seen from below by the surgeon during total knee arthroplasty with the knee flexed at 90°. The posterior condylar angle is the angle between the posterior condylar surfaces and the surgical epicondylar axis, defined by using the medial and lateral epicondyle. From: Berger RA, Rubash H, Seel M, Thompson W, Crossett L. Determining the rotational alignment of the femoral component in total knee arthroplasty using the epicondylar axis. Clin Orthop 1983;Jan(286):40-7. Lippincott Williams & Wilkins. http://www.lww.com. Reprinted with permission.42 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 3 Diagram representing the 2 flexion axes of the knee. Abbreviations: EF, extension facet, with the corresponding distal condylar facet; FF, flexion facet, with the corresponding posterior condylar axis; TAF tibial articular facet, where the lateral femoral condyle articulates with the tibia; M, medial; L, lateral. Reprinted with permission.25 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 4 The anatomy of the flexed knee showing the asymmetry of the joint. Ant., anterior; lig., ligament; post., posterior. Reprinted with permission.58 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 5 The location of the rotation axes of the knee. (A) Diagrammatic representation of axes in anteroposterior (AP) view with axis parallel to the plate. A is the angle the flexion-extension (FE) axis makes with the shaft of the femur (mean, 84°); B is the angle between the flexion-extension and left-right (LR) axes in the AP plane (mean, 88°). C is the angle between the longitudinal rotation (LR) axis and the tibial plateau (mean, 89°). (B) Diagrammatic representation of axes in sagittal view with x-ray beam parallel to the flexion-extension axis. E is the angle between the LR axis and the tibial plateau in the axial lateral plane (mean, 85°). From: Hollister A, Jatana S, Singh A, Sullivan W, Lupichuk A. The axes of rotation of the knee. Clin Orthop 1993;May(290):259–68. Lippincott Williams & Wilkins. http://www.lww.com. Reprinted with permission.20 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 6 Roll and glide movements of the femoral condyle. (A) Pure rolling motion: the femur rolls off the tibial plateau before full flexion is complete. (B) Pure sliding motion: the femur impinges the posterior tibial plateau before full flexion is achieved. (C) Combined rolling and gliding of the femoral condyles allows full range of flexion. Reprinted with permission.11 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 7 Schematic representation of the knee as a four-bar linkage system showing posterior displacement of the point of tibiofemoral contact with flexion. Reprinted with permission.11 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)

Fig 8 The position of femoral condyles on the tibial surface.22 Mean tibiofemoral contact positions of normal knees of (A) 4 female volunteers and (B) 10 male volunteers. Four positions are shown: early flexion (15° or 20°) with neutral rotation, 90° of flexion with neutral rotation (90° N), 90° of flexion with internal rotation (90° IR), 90° of flexion with external rotation (90° ER). From: Todo S, Kadoya Y, Moilanen T, et al. Anteroposterior and rotational movement of the femur during knee flexion. Clin Orthop 1999;May(362):162-70. Lippincott Williams & Wilkins. http://www.lww.com. Reprinted with permission.23 Archives of Physical Medicine and Rehabilitation 2003 84, 1895-1902DOI: (10.1016/S0003-9993(03)00281-8)