Knee Joint Anatomy and Function

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Questions and Answers

What type of joint is the knee classified as?

Ball and socket joint

Pivot joint

Gliding joint

Hinge joint (modified) (correct)

Which of the following terms describes a condition where the knees angle inward toward each other?

Patellar instability

Genu varum

Osteoarthritis

Genu valgum (correct)

What is the primary function of the menisci in the knee joint?

Enhance joint stability and provide shock absorption (correct)

Facilitate muscle movement

Act as synovial fluid

Provide blood supply

Which muscles are primarily responsible for extending the knee?

Quadriceps group Signup and view all the answers

What anatomical feature contributes to the stability of the knee joint?

Menisci and ligaments Signup and view all the answers

Which arteries provide the blood supply to the knee joint?

Branches of the popliteal artery and genicular arteries Signup and view all the answers

What does the ACL primarily prevent?

Anterior displacement of the tibia in relation to the femur Signup and view all the answers

What is the primary function of the PCL?

Prevent posterior translation of the tibia Signup and view all the answers

During which condition are the ligaments notably taut?

Full extension of the knee Signup and view all the answers

Which statement about the ACL and PCL is accurate?

The PCL is approximately three times thicker than the ACL. Signup and view all the answers

What can increase the risk of ACL injury during activity?

Sudden additional medial twisting when the foot is planted Signup and view all the answers

How does the blood supply to the ACL function?

It is supplied by branches of the middle genicular artery. Signup and view all the answers

What characterizes the red zone of the menisci in relation to healing capacity?

It has a direct relationship between vascularization and healing. Signup and view all the answers

What happens during the last 15° of extension in the knee?

Medial rotation of the femur occurs on the tibia. Signup and view all the answers

Which muscle is responsible for unlocking the knee joint from full extension?

Popliteus Signup and view all the answers

What occurs when the knee is locked in full extension?

The joint becomes solid and stable. Signup and view all the answers

What is the action of the popliteus muscle?

Laterally rotates the femur. Signup and view all the answers

Why is the medial meniscus more prone to injury compared to the lateral meniscus?

It is more frequently subjected to weight-bearing stress. Signup and view all the answers

During walking, what movement occurs to transition from knee flexion to extension?

Rolling and gliding within the joint. Signup and view all the answers

What anatomical feature does the popliteus muscle pierce?

Arcuate ligament. Signup and view all the answers

What is the primary function of the collateral ligaments in the knee joint?

Prevent sideways movement against varus or valgus forces Signup and view all the answers

Which ligament is described as having a flat strap-like structure?

MCL Signup and view all the answers

In what position are the collateral ligaments taut?

In full extension of the knee Signup and view all the answers

During normal walking, when does the body apply load to the knee joint?

In full extension Signup and view all the answers

Where does the lateral collateral ligament (LCL) attach?

To the lateral epicondyle and the head of the fibula Signup and view all the answers

What additional support is provided to the knee joint?

Menisci and tendons Signup and view all the answers

Which structure is anchored to the medial meniscus?

MCL deep band Signup and view all the answers

What is a characteristic feature of the medial collateral ligament (MCL)?

Has two distinct bands Signup and view all the answers

How does the position of the knee affect the collateral ligaments during movement?

They provide more support in extension Signup and view all the answers

What type of forces do the collateral ligaments resist?

Varus and valgus forces Signup and view all the answers

Study Notes

The Knee Joint Overview

The knee joint is a modified hinge joint.
It is stable due to the presence of intra and extra-capsular ligaments.
The articulation points include the patellofemoral joint and the medial and lateral tibiofemoral joints.
The knee is not ideally congruent, so there is a potential for the femoral condyles to slip off the plateaus.

The Knee Menisci

The menisci are intra-synovial articular discs that help create stability.
They are wedge-shaped and help deepen the socket for more congruency and support.
They also act as shock absorbers.

Muscles Crossing the Knee Joint

Muscles produce movement across the knee and enhance joint stability.
The anterior muscles (quadriceps group) extend the knee by crossing the knee via the patella.
The posterior muscles (hamstring, gastrocnemius, popliteus, and plantaris) perform other movements.

Normal Range of Movements of the Knee

The normal range of movement is 0-135 degrees.
Flexion and extension range from 30-40 degrees and 10 degrees respectively.
Pain, oedema, and muscle bulk can restrict this range.

Vasculature of the Knee Joint

Blood supply comes from the popliteal artery and its anastomoses.
There are five descending branches of the genicular arteries.
The popliteal artery branches from the femoral artery.

Red Zones of the Menisci

The red zone is more vascularised and heals better than other areas of the meniscus.

Tibio-Femoral Joint

The joint is fully flexed and pulled apart.
The most anterior part of the femoral condyle is reserved for the patella.

Tibio-Femoral Joint (cont.)

During walking, a combination of rolling and gliding occurs between the femur and tibia.
This causes medial rotation of the femur on the tibia in the final 15 degrees of extension.
The rotation tightens all the ligaments and creates a closed-packed position.

Popliteus Muscle

The popliteus muscle laterally rotates the femur to unlock the joint after full extension.
It attaches to the lateral femoral condyle and pierces the capsule.
The popliteus muscle is supplied by the tibial nerve.

Collateral Ligaments

The LCL is a thinner cord-like structure attached to the lateral epicondyle of the femur and the head of the fibula.
The MCL is a flat strap with two bands.
The superficial band runs from the medial epicondyle of the femur to the proximal shaft of the tibia.
The deep band is similar to the superficial, but also anchored to the medial meniscus.

Collateral Ligaments Function

The collateral ligaments prevent sideways movement against varus or valgus force.
They are taut in full extension and relaxed during flexion.

Additional Support

Additional support is provided by the pes anserine tendons, gastrocnemius, hamstring, biceps femoris, and iliotibial band.

Valgus Stress Test

The Valgus stress test assesses the MCL.
The test is performed with the knee in extension as this is when the ligament is subjected to the greatest stress.

Varus Stress Test

The Varus stress test assesses the LCL.

Cruciate Ligaments

The cruciate ligaments get their name from the Latin word "crux" meaning cross.
The ACL inserts into the anterior intercondylar ridge of the tibia and the lateral surface of the medial femoral condyle.
The PCL inserts into the posterior intercondylar ridge of the tibia and the lateral surface of the medial femoral condyle.

Anterior Cruciate Ligament

The ACL prevents the tibia from displacing anteriorly in relation to the femur.
It is under great stress during full extension.

Posterior Cruciate Ligament

The PCL prevents the tibia from displacing posteriorly and the femur from moving forward excessively.
The PCL is three times thicker than the ACL.
The tightness of the quadriceps muscle and the PCL work in tandem to prevent the femur from slipping forward.

Cruciate Ligament Injury

When the knee is extended, the ligaments are taut.
Sudden medial twisting can cause an injury to one or both cruciate ligaments.
The ACL is thinner, so it is more prone to injury.
The ligaments receive blood supply from the middle genicular artery, which forms a vascular synovial envelope.
If ruptured, they can leak blood inside the joint capsule, causing a haematoma.

The Lachman’s Test

The Lachman's test is used to evaluate an ACL rupture.
It is executed with the knee at 30 degrees to relax the hamstring.

The Unhappy Triad

The unhappy triad is the rupture of the ACL, MCL, and the medial meniscus.
It is usually caused by a lateral force or twisting in extension.

Synovium of the Knee Joint

The cruciate ligaments and the popliteal tendon lie outside the synovial membrane, although they are within the capsule.

Infrapatellar Fat Pad (Hoffa’s fat pad)

It is located outside the synovium behind the patellar tendon.
It acts as a cushion to prevent friction and fill the space for stabilisation.
It is richly vascularised.

Infrapatellar Fat Pad Attachments

The infrapatellar fat pad attaches to the patellar tendon and the superior aspect of the tibial plateau.

Bursae of the Knee Joint

Bursae are fluid-filled sacs found around the knee that protect tendons close to the bone.
The prepatellar bursa protects the skin.
Four bursae have a connection with the joint capsule – the suprapatellar, semimembranosus, gastrocnemius, and popliteal bursae.
The semimembranosus bursa and gastrocnemius bursa are often combined.

Popliteus Bursa

The popliteus bursa protects the popliteus tendon as it winds laterally under the LCL.
Enlargement of these bursae can cause swelling known as Baker’s Cyst.
Baker’s cyst commonly occurs with inflammatory reactions in late stages of knee osteoarthritis.

Anserine Bursa

It is the most common bursa affected by running, due to constant friction, excessive rotation, and valgus stress.

Suprapatellar Bursitis

Inflammation of the suprapatellar bursa can cause swelling over the top of the patella.

Pre-Patellar Bursitis

Inflammation of the prepatellar bursa, known as "housemaid's knee", can cause swelling over the patella.

Infrapatellar Bursitis

Inflammation of the infrapatellar bursa can cause swelling below the patella.

Treatment for Bursitis

Excess fluid is removed by aspiration.
NSAID agents are used to treat the inflammation.

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Description

This quiz covers the anatomy, biomechanics, and function of the knee joint. It includes details about the knee joint structure, the role of menisci, muscles involved in movement, and the normal range of motion. Test your knowledge on these important aspects of knee function!