joints of lower limb😭

Joints of the Lower Limb

Hip Joint

• Location: Between the lower limb and the pelvic girdle.

• Type: Strong and stable multiaxial ball and socket type of synovial joint.

• Articulation: Head of the femur (the ball) articulates with the acetabulum (the socket).

• Function: Designed for stability over a wide range of movement.

Articular Surfaces of the Hip Joint

• Articulation Details:

  • The round head of the femur articulates with the cup-like acetabulum of the hip bone.

  • Articular cartilage covers all of the femoral head except for the fovea for the ligament of the femoral head.

• Acetabulum Composition:

  • Formed by three bony parts.

  • The acetabular rim is a semilunar articular part covered with articular cartilage, known as the lunate surface.

Acetabular Features

• Acetabular Notch: Missing inferior segment of the circle.

• Acetabular Labrum:

  • A fibrocartilaginous rim attached to the margin of the acetabulum.

  • Increases the acetabular articular area by nearly 10%.

• Transverse Acetabular Ligament: Bridges the acetabular notch and is a continuation of the acetabular labrum.

• Non-Articular Part: Acetabular fossa, formed by the ischium.

Hip Joint Ligaments

• Fibrous Layer: Forms ligaments of the hip joint from the pelvis to the femur.

• Iliofemoral Ligament:

  • Strong, Y-shaped ligament located anteriorly and superiorly.

  • Attaches to the anterior inferior iliac spine (AIIS) and the acetabular rim proximally, and the intertrochanteric line distally.

  • Known as the body’s strongest ligament; prevents hyperextension of the hip joint during standing by screwing the femoral head into the acetabulum.

Other Ligaments

• Pubofemoral Ligament:

  • Located anteriorly and inferiorly.

  • Originates from the obturator crest of the pubic bone and merges with the fibrous layer of the joint capsule.

  • Prevents overabduction of the hip joint.

• Ischiofemoral Ligament:

  • Located posteriorly.

  • Weaker than the iliofemoral and pubofemoral ligaments.

  • Together with ligaments and peri-articular muscles, they maintain the structural integrity of the joint.

Blood Supply of the Hip Joint

• Main Vessels:

  • Medial and lateral circumflex femoral arteries (branches of the profunda femoris artery and femoral artery).

  • Artery to the head of the femur (branch of the obturator artery).

  • Retinacular arteries (branches of the circumflex femoral arteries).

Nerve Supply of the Hip Joint

• Hilton's Law: States that the nerves supplying the muscles extending directly across and acting at a given joint also innervate the joint.

• Innervations:

  • Flexors: Anterior aspect of the hip joint is innervated by the femoral nerve.

  • Lateral Rotators: Innervated by the obturator nerve (inferior aspect) and the nerve to the quadratus femoris (posterior aspect).

  • Abductors: Innervated by the superior gluteal nerve (superior aspect).

Knee Joint

• Description: Largest and most superficial joint.

• Type: Hinge type of synovial joint: allows flexion and extension combined with gliding, rolling, and rotation about a vertical axis.

• Implications of Hyperextension: Impairment of the knee joint; particularly relevant in contact sports such as ice hockey and football.

Articulations and Articular Surfaces of the Knee Joint

• Articulations: Three articulations exist within the knee joint:

  • Two femorotibial articulations (lateral and medial) between the femoral and tibial condyles.

  • One intermediate femoropatellar articulation between the patella and the femur.

• Fibula Involvement: Not involved in the knee joint.

Stability of the Knee Joint

• Weakness of Joint: Stability relies on the strength and actions of:

  • Muscles and their tendons.

  • Ligaments connecting the femur and tibia.

• Preventing Sport Injuries: Proper conditioning and training are key to preventing sports injuries.

• Quadriceps Femoris: The most important muscle in stabilizing the knee joint, particularly the vastus medialis and lateralis.

Joint Capsule of the Knee Joint

• Structure: Composed of an external fibrous layer and an internal synovial membrane.

• Fibrous Layer Functions: Forms intrinsic ligaments.

Extracapsular Ligaments of the Knee Joint

• Types: Five extracapsular (intrinsic) ligaments exist:

  • Patellar ligament.

  • Fibular collateral ligament (FCL).

  • Tibial collateral ligament (TCL).

  • Oblique popliteal ligament.

  • Arcuate popliteal ligament.

Specific Ligaments

• Patellar Ligament:

  • Distal part of the quadriceps femoris tendon.

  • Strong, thick fibrous band passing from the apex and margins of the patella to the tibial tuberosity.

  • Represents the anterior ligament of the knee joint.

• Fibular Collateral Ligament (FCL):

  • Strong cord-like extracapsular ligament that extends from the lateral epicondyle of the femur to the lateral fibular head.

  • Separates from the lateral meniscus by the tendon of the popliteus.

  • The tendon of biceps femoris is split into two parts by the FCL.

• Tibial Collateral Ligament (TCL):

  • Strong, flat, intrinsic band from the medial epicondyle of the femur to the superior part of the medial surface of the tibia.

  • Deep fibers attach to the medial meniscus.

  • Generally weaker than FCL and more frequently damaged during contact sports.

Additional Ligaments

• Oblique Popliteal Ligament:

  • Extension of the tendon of the semimembranosus.

  • Reinforces the joint capsule posteriorly; arises posteriorly to the medial tibial condyle.

• Arcuate Popliteal Ligament:

  • Strengthens the joint capsule posterolaterally.

  • From the posterior aspect of the fibular head; also contributes to posterolateral stability of the knee.

Intra-Articular Ligaments of the Knee Joint

• Composition: Comprised of cruciate ligaments and menisci.

• Functionality of Cruciate Ligaments:

  • Crisscross within the joint capsule but outside the synovial cavity.

  • Cruciate ligaments wind around each other during medial rotation of the tibia on the femur to act as a pivot for rotatory movements at the knee.

Anterior Cruciate Ligament (ACL)

• Description: Weaker of the two cruciate ligaments; arises from the anterior intercondylar area of the tibia.

• Poor Blood Supply: Leads to difficulty in healing.

• Attachment: Connects to the lateral condyle of the femur.

• Function: Prevents posterior displacement of the femur on the tibia and hyperextension of the knee joint.

Posterior Cruciate Ligament (PCL)

• Description: Stronger of the two cruciate ligaments; arises from the posterior intercondylar area of the tibia.

• Attachment: Connects to the medial condyle of the femur.

• Function: Prevents anterior displacement of the femur on the tibia or posterior displacement of the tibia on the femur; also helps prevent hyperflexion of the knee joint.

• Main Stabilizing Factor: The PCL primarily stabilizes the femur in a weight-bearing flexed knee position.

Menisci of the Knee Joint

• Description: Crescentic plates of fibrocartilage that deepen the articular surface of the tibia and play a role in shock absorption.

• Structure: Thicker at external margins, tapering to thin in the interior.

• Coronary Ligaments: Portions of the joint capsule that link the menisci and tibial condyles.

• Transverse Ligament of the Knee: Joins the anterior edges of the menisci.

Specific Menisci

• Medial Meniscus:

  • C-shaped, broader posteriorly than anteriorly.

  • Anterior end attaches to the anterior intercondylar area of tibia, and posterior end attaches to the posterior intercondylar area.

  • Adheres to the deep surface of the TCL; less mobile on the tibial plateau than the lateral meniscus.

• Lateral Meniscus:

  • Nearly circular, smaller, and more freely movable than the medial meniscus.

  • Involvement of the tendon of the popliteus, having two parts related to it.

  • Posterior meniscofemoral ligament joins the lateral meniscus to the PCL and medial femoral condyle.

Movements of the Knee Joint

• Primary Movements: Flexion, extension, and rotation.

• Knee Locking: Occurs when fully extended with the foot on the ground due to medial rotation of the femoral condyles on the tibial plateau, rendering the limb a solid column for weight-bearing.

• Knee Unlocking: Achieved when the popliteus contracts, rotating the femur laterally approximately 5° on the tibial plateau, allowing for flexion.

Blood Supply of the Knee Joint

• Main Vessels:

  • Genicular branches of the femoral, popliteal, and anterior/posterior recurrent branches of the anterior tibial and circumflex fibular arteries.

  • Middle genicular branches of the popliteal artery supply cruciate ligaments, synovial membrane, and peripheral margins of menisci.

Innervation of the Knee Joint

• Innervation Sources:

  • Articular branches from the femoral, tibial, and common fibular nerves supply anterior, posterior, and lateral aspects, respectively.

  • Obturator and saphenous nerves provide innervation to the medial aspect.

Bursae Around the Knee Joint

• Major Bursae: Prepatellar and infrapatellar bursae at the convex surface of the joint.

• Communication: Four bursae that communicate with the synovial cavity of the knee joint include:

  • Suprapatellar bursa.

  • Popliteus bursa (located deep to the distal quadriceps).

  • Anserine bursa (located deep to the tendinous attachments of sartorius, gracilis, and semitendinosus).

  • Gastrocnemius bursa.

• Clinical Note: Infections in the suprapatellar bursa may spread to the knee joint cavity.