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Biomechanics of Knee Joint

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Presentation on theme: "Biomechanics of Knee Joint"— Presentation transcript:

1 Biomechanics of Knee Joint
-Presented by Dr. Pranali Chougule MPT[Neuro] 1st year

2 ANATOMY

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5 TIBIOFEMORAL ALIGNMENT
The anatomical (longitudinal) axis of the femur is oblique, directed inferiorly and medially from proximal to distal end Angle is i.e femur is angled up to 50 creating slight physiological valgus angle >185= genu valgum <175= genu varus Mechanical axis or weight bearing line

6 MENISCI Relative incongruence of the tibiofemoral joint is improved by medial and lateral menisci by converting convex tibial plateau into concavities for femoral condyles

7 MENISCI CONT.. FUNCTIONS OF MENISCI Enhancing joint congruency
Distributing weight bearing forces Reducing friction between femur and tibia Serving as shock absorber

8 MENISCI CONT.. MEDIAL MENICUS- C- shaped
Medial meniscus covers a larger medial condyle thus more susceptible to injury from relatively greater compressive loads passes through medial condyle daily It has greater ligamentous attachments, limiting translations Relative lack of mobility of this contributes to greater incidence of injury

9 MENISCI CONT.. LATERAL MENISCUS Nearly complete circle
Covers a greater percentage of smaller lateral condyle Thus lateral condyle is less susceptible to the injury Has less ligamentous attachment Thus lateral meniscus is more mobile as compared to medial meniscus

10 MENISCI CONT.. The blood supply of menisci is greatest near periphery. Blood supply comes from the capillaries of synovial membrane and capsule Internally it is avascular

11 MENISCAL ATTACHMENTS

12 MENISCAL ATTACHMENTS

13 JOINT CAPSULE

14 LIGAMENTS Medial collateral ligament Lateral collateral ligament
Anterior cruciate ligament Posterior cruciate ligament Ligaments of posterior capsule Oblique popliteal ligament Posterior oblique ligament Arcuate ligments

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16 Medial collateral ligament
It has both superficial and deep parts Superficial- From the from medial femoral condyle and attaches to the medial aspect of the proximal tibia distally to the pes anserinus. Deep- continuous to the joint capsule from inferior aspect of the medial femoral condyle to the proximal aspect of the medial tibial plateau and medial meniscus

17 Medial collateral ligament cont..
Function- With knee flexion MCL is important for resisting excessive valgus stress (more in knee flexion compared to extension) Also important foe resisting lateral tibial rotation

18 2. Lateral collateral ligament
a cord like ligament that begins on the lateral epicondyle of the femur and joins with the tendon of the biceps femoris Extracapsular Function- responsible foe resisting varus stress more successfully in full knee extension

19 3. Anterior cruciate ligament
runs from anterolateral aspect of the medial intercondylar tibal spine And extends superiorly, laterally, and posteriorly and attaches to posteromedial aspect of the lateral femoral condyle Prone to injury Function- resists anterior translation of tibia on femur also provides rotatory stability

20 AMB- Anteromedial bundle
PLB- Posterolateral bundle

21 4. Posterior cruciate ligment
This ligament runs from the posterior surface of the tibia between the two posterior horns of the menisci it then runs superiorly and anteriorly and attaches to the lateral aspect of the medial femoral condyle. Much shorter and less oblique than ACL Function- resists posterior translation of tibia on femur when it is flexed Although maximum posterior translation of tibia occurs at 75-b 900 of flexion The popliteal muscle shares the function of PCL

22 Ligaments of posterior knee joint capsule
Oblique popliteal ligament

23 JOINT KINEMATICS Primary angular motion- Flexion and extension
In some amount Medial/Lateral rotation (internal /external rotation) and varus/valgus (adduction/abduction) motion occurs FLEXION/EXTENSION – Plane - sagittal Axis- horizontal line passing through femoral epicondyles Normal ROM of flexion is degrees and 5-10 degrees beyond 0 degree position (hyperextension)

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26 ARTHROKINEMATICS Flexion= when femur is flexing on a fixed tibia during initial knee flexion there is posterior rolling of femoral condyles on tibia with flexion continuation after 250 there is anterior gliding of femoral condyle over tibial plateaus

27 Flexion= when Tibia is flexing on a fixed femur
The tibia both rolls and glides posteriorly on relatively fixed femoral condyles (concave-convex rule)

28 Extension= Tibia on fixed femur
Tibial condyles roll and slide anteriorly on the convex femoral condyles

29 Extension= Femur on fixed tibia
While standing up from a deep squat position, the femoral condyles roll anteriorly and slide posteriorly on the relatively concave tibial condyles (convex- concave rule)

30 2. MEDIAL/LATERAL ROTATION
Axis- longitudinal runs through medial tibial intercondylar tubercle Medial condyle acts as pivot point while lateral condyle moves through a greater arc of motion Medial rotation= when tibia is rotating medially on femur then medial condyle of the tibia rotate only slightly and lateral tibial condyle moves anteriorly through larger arc of motion

31 Medial condyle Lateral condyle

32 2. MEDIAL/LATERAL ROTATION cont..
Lateral rotation= when tibia is rotating laterally over a femoral condyles then medial tibial condyles again moves only slightly and lateral tibial condyle moves larger distance posteriorly on relatively fixed lateral femoral condyle During both medial and lateral rotation the menisci will distort in the direction of movement of the corresponding femoral condyle Thus menisci continue to reduce the friction and distribute forces without resisting the motion

33 2. MEDIAL/LATERAL ROTATION cont..
Both medial and lateral rotation of tibia is available maximum at the 900 of flexion than full extension or full flexion At 900 of flexion the total medial and lateral rotation of tibia is approx 350 Lateral rotation> medial rotation

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35 3. Valgus (abduction)/ varus (adduction)
Plane- frontal plane Minimal motion It only 80 at full extension and 130 with 200 of knee flexion Excessive valgus or varus motion in knee can lead to ligamentous insufficiency

36 Coupled motions Biplanar intraarticular motion because of oblique orientation of knee axis motion Sagittal+ frontal plane motion Medial femoral condyle lies slightly distal to the lateral femoral condyle, thus physiological valgus angle in extended knee With knee flexion there is coupled varus motion i.e tibia moves from lateral to the femur to medial And with knee extension there is coupled valgus motion i.e tibia moves from medial to lateral to the femur

37 Locking of knee joint/ screw home mechanism
There is lateral rotation of tibia during final stages of knee extension which is not voluntary and not produced by muscular actions Thus called as automatic or terminal rotation In closed kinematic chain- During last 300 of non weight bearing knee extension ( ) the larger medial condyle stops rotating while the smaller lateral condyle continues rolling and gliding These results in medial rotation of femur on tibia , seen in last 5 degree of extension Open kinematic chain: lateral rotation of tibia on femur.

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39 Unlocking of knee joint
To initiate flexion, knee must be unlocked. A flexion force will automatically result in medial rotation of tibia over femur. Because the larger medial condyle will move before the shorter lateral condyle. [Ha yong et al. Screw-Home Movement of the Tibiofemoral Joint during Normal Gait: Three-Dimensional Analysis, 2015] Popliteus is the primary muscle to unlock the knee Its function is dependent on whether the lower extremity is in a weight-bearing or non-weight-bearing state; it is considered the primary internal rotator of the tibia in the non-weight-bearing state. [Scott et al, Anatomy, Bony Pelvis and Lower Limb, Popliteus Muscle]

40 Kinematics of patellofemoral joint
At 1350 of flexion, the patella contacts the femur primarily near its superior pole, in this position the patella rests below the intercondylar groove In this position, the lateral edge of the lateral facet and the “odd” facet of the patella share articular contact with the femur With 900 of flexion the contact region of patella starts to migrate over inferior pole

41 Kinematics of patellofemoral joint cont..
Between 90 and 60 degrees of flexion, the patella is usually engaged within the intercondylar groove of the femur. With this the contact area of patella and femur is maximum With of flexion patella loses much of its mechanical engagement with the intercondylar groove. Once in full extension, the patella rests completely proximal to the groove and against the suprapatellar fat pad. In this position, with the quadriceps relaxed, the patella can be moved freely relative to the femur.

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43 Kinematics of patellofemoral joint cont..
Patellar Shifting Along with patellar flexion and extension the patella shifts medially and laterally in frontal plane This medial and lateral shift is named on the direction in which patella moving in reference to femoral condyles

44 Kinematics of patellofemoral joint cont..
Medial and Lateral Patellar Rotation With knee flexion there is medial rotation of tibia on femur along with this there is medial rotation of patella approx 50 with of flexion

45 Muscles KNEE FLEXOR GROUP
There are seven muscles that cross the knee joint posteriorly Semimenbranosus Semitendinosus Biceps femoris (short and long head) Sartorius Gracialis Popliteus gastrocnemius

46 Knee flexors Five of the flexors (the popliteus, gracilis, sartorius, semimembranosus, and semitendinosus muscles) rotates tibia medially over a fixed femur And biceps femoris rotates tibia laterally over a fixed femur

47 Knee flexors cont.. The lateral muscles (biceps femoris, lateral head of the gastrocnemius, and the popliteus) produce a valgus torque whereas those on the medial side of the joint (semimembranosus, semitendinosus, medial head of the gastrocnemius, sartorius, and gracilis) can generate varus moments

48 Knee flexors cont.. Hamstrings- flexors
Greater hamstring force is produced with the hip flexed because the hamstrings are lengthened across the hip In non-weight bearing knee flexion, the hamstrings generate a posterior shearing force of the tibia on the femur that increases as knee flexion increases more in of flexion This posterior shear or posterior translational force can reduce strain on the ACL, although conceivably it increases the strain on the PCL

49 Knee flexors cont.. Gastrocnemius muscle is also important in maintaining the dynamic stability of the knee joint the knee joint has to be positioned close to, or beyond, 165° to take advantage of the gastrocnemius greater contribution to the knee flexion moment. [Li Li et al, The function of gastrocnemius as a knee flexor at selected knee and ankle angles, 2002]

50 Knee flexors cont.. Sartorius function as flexor and medial rotator of tibia Pes anserinus provide dynamic stability to the anteromedial aspect of the joint The popliteal muscle is medial rotator of tibia on femur to unlock the knee

51 Knee flexors cont.. In weight bearing position the soleus assists in knee extension by pulling tibia posteriorly Also the gluteus max assists in knee extension by pulling femur posteriorly on tibia

52 KNEE EXTENSOR GROUP 4 extensors of knee Rectus femoris Vastus lateralis Quadriceps Vastus medialis Vastus intermedius The resultant pull of vastus lateralis muscle is 350 laterally and that of vastus medialis is 400 medially

53 Knee extensors Vastus medialis- the upper fibers are angled medially to the femoral shaft whereas the distal fibers are angled medially thus the upper fibers are called as Vastus medialis longus(VML) and lower fibers as Vastus medialis oblique(VMO) The VMO maximize its medial pull on patella

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55 Patellar influence on quadriceps
Patella acts as a anatomic pulley for quadriceps as it lengthens the moment arm of the quadriceps . The patella deflects the action line quadriceps muscle increasing the angle of pull on tibia, enhancing the ability of quadriceps extension torque With knee extension the moment arm will diminished

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57 Patellofemoral stabilization
As the knee flexes the quads tendon pull patella superiorly and this pull is resisted by patellar tendon These forces generate posterior compressive force of patella on femur The resultant pull of quads and patellar tendon provides the information about net force on patella in frontal plane

58 Patellofemoral stabilization cont..
Because of physiological valgus at the knee joint there is resultant lateral pull on patella in extension Longitudinal stabilizer of patella- patellar tendon inferiorly and quads superiorly Transverse stabilizers- vastus lateralis and vastus medialis

59 Patellar stability in frontal plane
Q angle- angle formed between a line connecting the ASIS to the midpoint of the patella (representing the direction of pull of the quadriceps) and a line connecting the tibial tuberosity and the midpoint of the patella

60 Normal = Increased Q angle= Increased lateral force on patella

61 References Cynthia Norkin, Joint structure and function, 5th edition
Newman, kinesiology of musculoskeletal system, 2nd edition Carol Otis, Kinesiology, mechanics and pathomechanics of human movement, 2nd edition Ha yong et al. Screw-Home Movement of the Tibiofemoral Joint during Normal Gait: Three-Dimensional Analysis, 2015 Scott et al, Anatomy, Bony Pelvis and Lower Limb, Popliteus Muscle Li Li et al, The function of gastrocnemius as a knee flexor at selected knee and ankle angles, 2002

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