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Re: BioNet Controversial Topic #4: knee joint DoUF

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  • Re: BioNet Controversial Topic #4: knee joint DoUF

    The knee joint has one degree of freedom that deserves special
    mention in my eyes (disclaimer - I am a forensic pathologist and no
    biomechanics expert):

    Other than rotation (2 directions: inward, outward), coronal
    angulation (2 directions: abduction, adduction) and sagittal
    angulation (2 directions: flexion, extension), the kneejoint offers
    yet another degree of movement that is very small compared to the
    just-mentioneds: axial movement (2 directions: compression,
    distension). Like with the other movements, I would suppose that
    there is a position dependent set of three joint-position-dependent
    parameters: lax range, restricted range and mechanical threshold
    (above which injury occurs).

    The healthy lax range would be - estimated by me - around 1 mm at the
    utmost. However, ligamental injury will drastically increase this
    type of axial movement - up to a degree where one may call it
    "unrestricted". More people walk around with untreated cruciate
    ligament injuries than meets the eye and such risk so-called
    "secondary" injuries.

    As in any degree of motion being linked to certain "typical" injuries
    known to occur in certain typical injury - positions, the axial
    movement could be linked to meniscal injuries, chondral surface
    injuries, and - feared the most among some skiers, I would think -
    tibial compression fracture with or without joint surface involvement.

    Secondly, any parameters are not only joint-position dependent, but
    the knee stabilisation is heavily relying on muscle action - rather
    than ligament/meniscus action - only surpassed by the shoulder joint
    as far as I would know, which is almost completely muscle-stabilised.
    The mix of lig/menisc. stabilisation vs. muscular stabilisation is
    dependent on the joint position as well.

    That is also the reason why it is "sort of ok" not to fix ligamentary
    knee injuries since the muscle training is a compulsory follow-up of
    the injury anyway (with or without operation). It therefore means
    that the concise degree of freedom is not only joint-position
    dependent, but also muscle-action dependent. Amount of training (very
    important), muscle warm-up, alertness or tiredness are the major
    components as far as I would guess.


    Wolf Schweitzer, MD
    FMH Legal Medicine

    >Dear Colleagues,
    >After a good start with the discussions of the controversial issues in
    >biomechanics (TOPICS 1, 2 and 3), here we are with the launch of a
    >TOPIC 4 for this series. This Topic seems particularly indicated for one of
    >the discussion workgroups within Session "Get it Off Your Chest" at the
    >Event in Bruxelles ( As usual, we
    >invite all contributors to formulate their own opinions and comments. Sorry
    >in advance for any possible missing work of other important contributions
    >from the literature in this respect: this is a good opportunity to collect
    >all relevant views and eventually to make a summary.
    >on behalf of the BIONET Consortium
    >Alberto Leardini
    >The BioNet event is approaching quickly. I'd like to remind to all
    >prospective attendees that "Early Bird" Registration ends on 28th March!!
    >Go and see the faschinating programme.
    > T O P I C # 4
    >How many independent degrees of unresisted freedom has the human knee joint?
    >What's the matter
    >Under load, the knee, as every human joint, shows important motion, i.e.
    >both rotations and translations can occur, no matter on the extent of this
    >motion. It is however also well documented that the resistance offered by
    >the joint to externally imposed displacements and rotations is different
    >from an anatomical plane to another, and from one direction to another
    >(flexion is less resisted than ab/adduction, antero-posterior displacement
    >less than separation/penetration, separation less than penetration, etc.).
    >It is clear that this resistance is offered even before any muscle
    >activity, for example even on cadavers, therefore it must be provided
    >primarily by the joint passive structures. It has also been shown that this
    >resistance changes also from joint position to joint position. The
    >questions are: how many independent degrees of freedom has the human knee
    >joint? Are there series of joint positions at stable equilibrium, that is
    >positions in which resistance is not offered by the joint until an external
    >displacement is performed? Are these positions in large combinations or a
    >narrow path of unresisted motion is prescribed? Because we want to
    >characterise the joint in itself, these questions should be addressed by
    >looking at passive motion, i.e. in virtually unloaded conditions, therefore
    >the number of 'degrees of unresisted freedom (DoUF)' is here under
    >discussion. This parameter represents therefore the number of input
    >quantities required to specify fully the relative position of the two
    >segments involved when motion of the joint is observed in the condition of
    >virtually absence of external forces. Note all these considerations are
    >unaffected by the type and complexity of the motion performed, whether this
    >is a ball-and-socket or hinge-like or a complex mechanism or whatever.
    >Does it matter?
    >Characterising the knee (as any of the human diarthrodial joints) according
    >to the number of DoUF may seem merely an academic exercise, but in fact it
    >is a fundamental question for any new investigation on the joint mobility
    >and stability by geometrical and mechanical models. This knowledge is very
    >useful in modelling studies because it determines the most appropriate
    >approach for the analysis. Knowing the joint is a flexible structure (0
    >DoUF), structural mechanics can immediately be applied to combine external
    >load and relevant displacements/rotations in the single resisted joint
    >position (as the vertebrae?). With a single DoUF, the joint can still be
    >cylindrical (hinge-like, elbow?). If, conversely, the articular surfaces
    >become incongruent during motion, and if some rolling occurs and a moving
    >instantaneous axis of rotation is observed, this may suggest that the joint
    >is constrained in a single DoUF 'mechanism'. In two or three (hip?) DoUF
    >joints, a large spectrum of unresisted positions are allowed, and joint
    >resistance is felt only when close to the extremes of the range of motion.
    >If the number of DoUF at the knee is more than 0, a profound knowledge of
    >these series of joint positions would be a necessary preliminary part of
    >any study addressing knee mechanics. It is also evident that any change to
    >the original geometry of the intact joint, such as erosion of the articular
    >surfaces, ligament injury and reconstruction, or total joint arthroplasty,
    >will alter the original number of DoUF and lead to abnormal kinematics of
    >the joint.
    >>From the literature
    >Since the first observations of the screw-home mechanism of the knee,
    >scientists and clinicians have given up the idea that this joint is a
    >simple mechanical pair, such as an hinge or a ball-and-socket joint
    >[1,2,3,4,5,6]. Therefore in modern biomechanics the knee translations and
    >rotations are usually described along and about the 3 anatomical axes, both
    >during passive and weight-bearing motion [13,14,15,16]. In clinical
    >practice and standard gait analysis, either for diagnostic purposes or to
    >evaluate surgical treatments, clinicians consider separately the 3
    >rotations and the 3 translations at the knee, alluding implicitly to 6
    >independently degrees of freedom, no matter on whether these are coupled or
    >In 1907 Fisher stated that "the knee has 2 dof" referring to the
    >flexion-extension and the internal-external rotation [7]. Also Hollister
    >[8], Freeman and Pinskerova et al. [9] have recently proposed that the knee
    >motion is the result of a combination of 2 rotations around an appropriate
    >axis of flexion-extension (located with respect to femoral anatomy, roughly
    >joining the centres of the two condyles) and an axis of longitudinal
    >rotation (described with respect to the tibial anatomy and roughly parallel
    >to the tibial shaft), without mentioning eventual translations occurring
    >during the motion. In [10,11] Wilson et al. concluded that the "passive
    >knee flexion can be described by a coupled path", and predicts that the
    >knee motion is prescribed by ligaments and articular surfaces alone along a
    >path [11], thus alluding at a single DoUF. Both statements however, [9] and
    >[10-11], allude to a single DoUF, although with different views on the type
    >of motion. On the other hand, ``envelopes'' of motion for was reported for
    >the knee joint [14] by the limits of internal and external tibial rotation
    >at a series of flexion angles when the tibia was subjected to 3~Nm of
    >internal and external torque. The motion was presented as an ``envelope''
    >because no consistent path was found in the completely unloaded state.
    >Confirming or contrasting evidence or opinions on this issue are welcome.
    >The issue is still open to any possible solution. Devising
    >methods/experiments to draw robust conclusions is also valuable for the
    >[1] Weber W, Weber E: Mechanics of the human walking apparatus.
    >Springer-Verlag, New York 1991 (translated from German by P. Maquet and
    >R. Furlong - from original work in 1836).
    >[2] Langer K., Das Kniegelenk des Menschen. In Sitzungsberichte der
    >Akademie der Wissenschaften. Mathematisch - Naturwissenschaftliche
    >Classe, Bde 2, 3. Wien, Karl Gerolds Sohn, p. 99, 1858
    >[3] Bugnon E., Le m├ęcanisme du Genou., Lausanne, CH Viret-Genton, 1892
    >[4] Fick R., Mechanik des Gelenkes, in Handbuch del Anatomie und
    >Mechanik der Gelenke. Jena, Gustav Fischer , 1911
    >[5] Pinskerova V, Maquet P, Freeman MA :"Writings on the knee
    >between 1836 and 1917", J Bone Joint Surg Br. 2000 Nov;82(8):1100-2 .
    >[6] Pio A., Carminati L., Stennardo, Pedrotti L :"Evolution of the
    >concepts of functional anatomy of the knee joint", Chir. Organi Mov.
    >1998, LXXXIII, 401-411 .
    >[7] Fischer O., Kinematik Organischer Gelenke. Braunschweig, F. Vieweg
    >und Sohn, 1907.
    >[8] Hollister, A.M., S. Jatana, A.K. Singh, W.W. Sullivan, A.G.
    >Lupichuck: "The axes of rotation of the knee", Clinical Orthopaedics and
    >Related Research, 290:259-268, 1993
    >[9] Pinskerova V., Freeman MA et al :"Tibiofemoral movement 1/2/3/4",
    >Bone Joint Surg Br. 2000 Nov;82(8):1189-95 / 1196-8 / 1199-200 / 1201-3.
    >[10] Wilson DR, Feikes JD, Zavatsky AB, O'Connor JJ.: "The components
    >of passive knee movement are coupled to flexion angle", J Biomech ,
    >33(4):465-73, 2000.
    >[11] Wilson DR, Feikes JD, O'Connor JJ. "The Ligaments and articular
    >surfaces guide passive knee flexion", J Biomech, 31:1127-1136, 1998.
    >[12] Piazza SJ, Cavanagh PR: Measurement of the screw-home motion of the
    >knee is sensitive to errors in axis alignment. J Biomech 33:1029-1034, 2000.
    >[13] Grood, E.S., W.J. Suntay,. A joint coordinate system for the
    >clinical description of three-dimensional motions: application to the
    >knee. Journal of Biomechanical Engineering., 105:136-144, 1983.
    >[14] Blankevoort, L.R Huiskes, A. De Lange. Helical axes of passive
    >knee joint motions. Journal of Biomechanics, 23:1219-1229, 1990.
    >[15] Pennock, G.R., K.J. Clark. An anatomy-based coordinate system
    >for the description of the kinematic displacements in the human knee.
    >Journal of Biomechanics, 23:1209-1218, 1990.
    >[16] Martelli S., S. Zaffagnini, B. Falcioni, M. Marcacci.
    >Intraoperative kinematic protocol for knee joint evaluation. Computer
    >Methods and Programs in Biomedicine, 62:77-86, 2000.
    >************************************************* *************************
    >Alberto Leardini, DPhil
    >Movement Analysis Laboratory
    >Centro di Ricerca Codivilla-Putti
    >Istituti Ortopedici Rizzoli
    >Via di Barbiano 1/10, 40136 Bologna ITALY
    >tel: +39 051 6366522
    >fax: +39 051 6366561
    >"Where is the Life we have lost in living,
    > Where is the wisdom we have lost in knowledge,
    > Where is the knowledge we have lost in information."
    >Thomas Stearns Eliot, Choruses from ''The Rock'' (1934)
    >************************************************* *************************
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    Wolf Schweitzer
    Dr. med., Facharzt Rechtsmedizin FMH
    Wissenschaftlicher Mitarbeiter
    Institut fuer Rechtsmedizin
    Winterthurerstrasse 190
    8057 Zuerich, Schweiz
    Tel. ++41 1 635 56 22

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