EMORY DPT ADVANCED EXTREMITIES: Knee Anatomy and Biomechanics

Describe the Knee Muscle Function of the Hamstrings

•60-70% strength of quadriceps Eccentric Contraction •Decelerate leg during late swing phase of walking •Dampens impact of full knee extension Concentric Contraction •Accelerate leg during swing phase of walking •Shortens limb and clears toes during initial swing phase of walking Isometric contraction •Stabilizes and helps protect knee

Describe the Arcuate complex

•Arcuate ligament •Lateral Collateral Ligament •Popliteus tendon •Lateral head of gastrocnemius •Biceps femoris

Describe the Genicular Nerves

•Articular branches from femoral, obturator, saphenous, common peroneal, tibial - Surround the knee, provide innervation to joint •Provide sensory only - Can be a contributor to persistent joint pain

describe the Saphenous Nerve

•Branch of of femoral nerve (L2-4) •ONLY sensory •Medial articulation of knee joint •Cutaneous sensation of knee, lower leg, ankle •

What is the Secondary Restraint of the knee in the frontal plane?

Valgus forces = Semimembranosus tendon ACL, PCL Compression of lateral meniscus Medial retinacular fibers Pes anserinus Gastrocnemius (medial) Varus forces = Arcuate complex IT band Biceps femoris tendon Compression of medial meniscus ACL, PCL Gastrocnemius (lateral)

Describe the soft tissue surrounding the patella

Patellofemoral ligaments Retinacular fibers patellotibial ligaments meniscal ligaments

Describe the Resting and closed packed position of the Knee and Tibiofibular joint.

The resting position of the knee joint is ~30 degrees of flexion while the closed pack position is full extension. The tibiofibular joint is 10 degrees of ankle plantar flexion while the closed pack position is maximal dorsiflexion

Describe the Joint arthrokinematics of the Knee

The tibiofemoral joint functions as a convex femoral condyle on a concave tibial plateau. The patellofemoral joint functions as a concave patella on a convex femoral condyles The tibiofibular joint functions as a concave fibula on a convex tibia

Describe the Knee joint complex planes of motion

The tibiofemoral joint moves parallel to the superior surface of the tibial plateau The patellofemoral joint moves to the posterior surface of articulating facets of the patella The tibiofibular joint moves parallel to the surface of the fibula

What components make up the knee joint?

Tibiofemoral Patellofemoral Tibiofibular

(T/F) The Femur Translates while it moves on the Tibia

True

Describe the forces acting on patella

when starting to think about a tracking issue we must look holistically at the entire joint

Describe the screw home mechanism

- locks the knee - final 30 degrees = external tibial rotation and anterior glide due to the tension of both cruciate ligaments - tibia in position of maximal stability - allows relaxation of quads while standing

Describe Plica

A fold in the synovial lining present in % of cases Infrapatellar plica is more clinically relevant due to its locations

Describe the Meniscus of the Knee

A wedge-shaped fibrocartilage with a vascular supply along the outer rim where the outer 2/3 contain a blood flow, neural innervation, and mechanoreceptors but the inner 1/3 lacks those. Location of lesion will affect healing prognosis (white on white vs red on white The function of the Menisci is to reduce tibiofemoral compressive forces while improving joint "fit" or stability during movement, lubricates articular cartilage, reduce friction, and guide arthokinematics at the tibiofemoral joint

What is the relationship between the ACL and the hamstrings?

if the hamstrings are in spasm that will limit anterior translation and lead to a false negative on the anterior drawer test. If the ACL is deficient then training the hamstrings may assist in that area of stability

Describe the Patellofemoral Joint

Diarthrodial plane joint where the central ridge pf the patella slides along the central groove of femur during movement while being stabilized by the quadriceps tendon, articular joint surfaces and retinacular fibers

Describe the forces caused by Genu valgum or varum

Dotted black line is angle to force from hip to knee More compressive force on lateral portion in valgum More compressive force on medial portion in varum

What type of joint is the tibiofemoral joint?

Double condyloid joint meaning that it has 3 degrees of freedom with stability gained from reinforcement by the tendons, ligaments, capsule, and menisci

Describe the Knee Muscle Function of the Quadriceps

Eccentric contraction •Control rate of descent in knee flexion •During initial contact, it controls flexion and acts as a spring to help dampen the impact of loading on the joint Concentric contraction •Knee extension •Raises body's COM during running, jumping or standing from a seated position Isometric contraction •Stabilizes and helps protect knee

Describe the Knee Joint Complex Capsule

Encompasses a large region including the tibiofemoral and patellofemoral joint. The synovial membrane contains synovial fluid and attached to the periphery of the following: - cartilage of tibia/femoral condyles - Posterior Patella - Edges of menisci

(T/F) The Menisci are static structures

False - motion occurs, lateral more than medial

(T/F) The tibial articular surface is symmetrically concave

False - the articular surfaces has a medial concavity and a lateral slight convexity

Arthrokinematically, flexion at the knee joint requires what type of glide? Extension requires what type of glide?

Flexion = distal glide of patella Extension = proximal glide of patella

Describe the tibiofemoral alignment

Frontal Plane knee position can be described as genu valgum (knock knee <165 degrees) and genu varum (bow leg or >180 degrees) In the sagittal plane the knee position can be described as genu recurvatum which can lead to posterior chain strain due to anterior stress

Describe patella contact in the following movements: Full Extension = 20-90 degrees of flexion = 90 degrees of flexion = > 90 degrees of flexion = 135 degrees of flexion =

Full Extension = contact above the femur at the fat pad 20-90 degrees of flexion = area of contact on condyles increases as flexion increases 90 degrees of flexion = superior portion of patella in contact with trochlea > 90 degrees of flexion = patella rides into the intercondylar notch 135 degrees of flexion = odd facet in contact with femoral condyle the more contact we have the more joint compression

Describe the positional changes relative to the patella in OKC and CKC

In OKC the patella moves In CKC the femur moves on the patella

Describe the end feel of the tibiofemoral joint?

In flexion the joint has a soft end feel due to the approximation of calf and posterior thigh however tightness in the Vastus Lateralis, Medialis, and Intermedius can contribute In extension the end feel is firm due to the posterior capsule tension, Arcuate popliteal ligaments, collateral ligaments, and the Collateral ligament tension

Describe the Patellofemoral Alignment

In the frontal plane the patellofemoral joint is describe as the Q-angle which is characterized by the ASIS to mid-patella; mid-patella to tibial tubercle. Normally this is between 10-15 degrees. In the sagittal plane the patellar is either Baja (too low) or Alta (too high)

What muscle assists in unlocking the knee from the screw home position?

popliteus -To "unlock" tibia must internally rotate to unlock knee

What is the primary restraint of the knee in the frontal plane?

MCL for Valgus forces and LCL for varus forces

Describe the Pes Anserine

MCL is deep but closely related to the Pes Anserine

Where are the ACL and PCL anchored?

ACL is anchor on the anterior aspect of the tibia PCL is anchored on the posterior aspect of the tibia

In what positions will the ACL and PCl be taught respectively?

ACL will be taught in extension PCL will be taught in flexion

Describe the Popliteus Muscle

An Intracapsular muscle that originates at the Lateral Condyle of Femur and inserts at the posterior proximal tibia Action is to initiate flexion and unlock knee

Describe the Lateral Collateral Ligament (LCL)

An extracapsular Ligament that is a stronger and thicker cord that attaches along side the biceps femoris tendon. Its function is to resist varus forces (Medial to lateral forces)

Describe the Medial Collateral Ligament (MCL)

An extracapsular ligament made of 3 segments; Superficial, Deep, and Posterior Oblique. The deep portion is made of the Medial capsular ligaments; Meniscofemoral and meniscotibial The function of the MCL is the resist valgus forces (lateral to medial force)

Describe the Anterior Cruciate Ligament (ACL)

An intracapsular and extra synovial ligament made of two bands Anteriormedial (taught is flexion) and Posterolateral (taught in extension while limiting rotation). Its function is to prevent posterior translation of femur on tibia and anterior translation of tibia on femur

Describe the Stability of the knee Joint

Anterior region stability is created by patellar tendon and retinacular fibers and muscularly by quadriceps The lateral region stability is created by the LCL, IT Band, and Lateral retinacular fibers and muscularly through the biceps femoris, popliteus tendon and lateral head of the gastroc. The Posterior region stability is created by the Oblique popliteal ligament and Arcuate popliteal ligament and muscularly by Popliteus, gastroc, and hamstrings. The posterior-lateral region stability is created by Arcuate popliteal ligament and LCL and muscularly by popliteus. The Medial region stability is created by the Medial Patellofemoral ligament, MCL, and Posterior obqlique ligament and muscularly by semimembranosus tendon, gracilis tendon, sartorius tendon, and semitendinosus tendon

Describe the ways in which the knee reduces friction

Bursae: an extension of synovial membrane formed external to the capsule at the intertissue junctions encountering high friction. Can become inflamed due to excessive repetitive actions Fat Pad: Located Suprapatellar and infrapatellar as well as posterior to patellar tendon and anterior to knee capsule. Hoffa's Fat Pad is an infrapatellar structure that is commonly inflamed or impinged They are richly innervated

Describe the Secondary Ligaments

Coronary Ligaments •Attaches menisci to tibia (deep) Transverse Ligaments •Connects two menisci anteriorly Posterior Meniscofemoral Ligament •Attaches lateral meniscus to femur •"Ligament of Wrisberg"

Due to the function of the patella as a sesamoid bone describe the complications that occur when the patella is not properly moved

The proper function of the patella is to increase the moment arm which subsequently decrease the load of the quadriceps. The picture on the right shows what happens when this is not the case where the quad is working harder due to the lack of biomechanical advantage provided by the increase moment (angle of pull) produced by the patella

Describe the Proximal Tibiofibular joint

Synovial Plane Gliding (syndesmosis) joint The joint is characterized by being between the flat facet on the head of the fibula and an articular facet on the posterolateral aspect of the lateral tibial condyle. here the Fibula is concave where as the Tibia is relatively convex. The joint is strengthened by the anterior and posterior tibiofibular ligaments and popliteus tendon. This joint functions to stabilize the tibia

Describe the Posterior Cruciate Ligament

The PCL is an instracapsular yet extra synovial ligament made of two bands; Posterior medial (taught in extension) and Anteriolateral (taught in flexion) Its function is to prevent anterior translation of the femur on the tibia and posterior translation of the tibia on the femur

Compare/Contrast the medial and lateral mensici

The medial Mensici is larger in diameter (C-shaped) and more securely attached to MCL and semitendinosus. Typically this menisci is injured more often. The lateral Menisci is "O-shaped" and more mobile and is attached to the PCL and popliteus

Describe how the position of the hip can affect the position of the knee

coxa vara may lead to genu valgum