This document provides an overview of the biomechanics of the knee complex. It describes the knee as the largest and most complex joint, consisting of the tibiofemoral and patellofemoral joints. The knee functions to flex and extend the leg, support body weight, and facilitate locomotion. Key components include the articular surfaces, menisci, capsule, collateral and cruciate ligaments, muscles, bursae, and plicae. The document outlines the roles and mechanics of each of these structures, as well as common injuries associated with the knee.
4. Functions:
Functional shortening and lengthening of the
extremity by flexion and extension
Supports body during dynamic and static activities
Closed kinematic chain- support body weight in
static erect posture
Dynamically- moving and supporting body in
sitting and squatting activities, supporting and
weight transferring activity during locomotion
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13. Menisci: Functions
Improves congruence of joint
Distributes weight bearing forces
Decreases friction between tibia and femur
Shock absorber
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14. Nutrition
First year of life: contains blood vessels
throughout meniscal body
Vascularity decreases with age
Outer 25% is vasularized by capillaries from
joint capsule and synovial membrane
Central blood supply by diffusion from
synovial fluid
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15. Prolonged immobilization or
non-weight bearing?
Menisci does not receive appropriate nutrition
Avascular nature of central portion of meniscus
reduces potential of healing after injury
In adults only peripheral portion of meniscus is
vasularized hence is capable of inflammation,
repair and remodeling after injury or tear.
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16. Compression forces at the knee:
While walking- 2.5 – 3 times body weight
Ascending stairs: 4 times
Menisci triples the surface area by significantly
reducing the pressure on the articular cartilage
Lateral menisectomy increases pressure at knee
by 230%
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Neumann, 2010
17. Mechanisms of meniscal injury
Forceful, rotation of femoral condyle on partially
flexed and weight bearing knee
locked knee syndrome
Medial meniscus is injured twice as much as
lateral
Risk of meniscal injury increases with instability
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18. Test for Miniscal injury
Apley’s Grinding Test
McMurray’s Test
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23. Capsule:
Synovial layer
Internal surface of the capsule is lined by
synovial membrane.
Role:
1. secretion of synovial fluid
2. Absorption of fluid into joint for lubrication
3. Nutrition to avascular structure like menisci
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25. Medial collateral ligament (MCL)
• Originates from medial
epicondyle of femur
• Inserted into medial tibial
plateau, medial
meniscus, medial
proximal tibia.
• Restrains excess
abduction and lateral
rotation stress at knee
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26. MCL: Applied aspect
Injury when valgus stress is
delivered over a planted foot.
Common in football players
MCL is rich in blood supply hence
has good healing
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27. Lateral collateral ligament (LCL)
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Extracapsular
Origin: Lateral femoral
condyle
Insertion: fibular head
Checks Varus stress
and excessive lateral
rotation of tibia
30. Anterior Cruciate Ligament
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Inferior attachment: anterior tibial spine
Extends superiorly, posteriorly to attach to the
postero-medial aspect of the lateral femoral
condyle
Two bands:
Anteromedial band (AMB)- taut in flexion
Postero-lateral band (PLB)- taut in extension
31. Anterior Cruciate Ligament
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Functions:
Restrains anterior translation of tibia on femur
Prevents hyperextension of knee
Secondary restraint against varus and valgus
motion
32. Mechanism of injury- ACL
Most common injury
Football, downhill skiing, basketball and soccer
players
Mechanism:
Common in weight bearing, slight flexion and
rotation in either directions
Anterior translatory force on proximal tibia
Hyperextension injury
Hyperflexion in bulky lower extremity muscles
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33. Posterior Cruciate Ligament
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• Origin: Posterior inter-condylar area of tibia
• Insertion: Lateral side of Medial femoral
condyle
• Anteromedial and posterolateral bands
34. Functions- PCL
Primary restraint to posterior translation of
tibia on femur
Limits the anterior translation of femur over
fixed tibia in activities such as rapid
descending into squat and landing from jump
with partially flexed knee
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35. Mechanism of injury- PCL
Three mechanisms
1. Pretibial trauma (Dashboard trauma)
2. Hyper flexion (in thin individual)
3. Hyperextension (second ligament to be
injured after ACL)
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37. Other ligaments
Oblique popliteal ligament
Anterolateral ligament (newer ligament)
List out all other ligaments and its function
referring to articles and reference text books
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39. Bursae
14 bursae
Reduce friction between intertissue junction
during movement.
Activities that involve excess and repetitive
force at inter tissue junctions frequently leads
to Bursitis.
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43. Plicae
Synovial membrane formation occurs in early
embryonic development
Synovial membrane separates medial and lateral
articular surface into separate cavities
By 12th week of gestation synovial septae
reabsorbs to form a single joint cavity
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44. Plicae
Failure of complete resorption results in
persistent folds called PLICAE
Plicae may get inflamed or irritated-
Plicae Syndrome
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46. References:
Neumann DA. Kinesology of musculoskeletal
system, Foundation for Physical Rehabilitation ,
2nd Edition
Norkin C, Levengie P. Joint structure and
function. 4th Edition
Kapandji IA. The Physiology of Joints. Volume 2,
Lower Limb. 5th Edition
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Editor's Notes
In unilateral stance or during gait, weight bearing line must shift medially across the knee to account or to compensate for small BOS below the centre of mass. This shift increases compressive forces on medial compartment.
Genu valgum:
Mechanical axis shifts laterally
Increased compressive forces laterally and tensile forces medially
Lateral OA and medial laxity of structures
Genu varum
Mechanical axis shifts medially
Increased compressive forces medially and tensile forces laterally
Medial OA and lateral laxity of structures
Locked knee syndrome- Torsion within the compressed knee can pinch and dislodge the meniscus. This can block knee movement causing locked knee.
Medial meniscus is larger and less mobile, so more chances of injuries