Joints of the Lower Limbs

Acetabulofemoral (Hip) Joint

The following are some notes on the acetabulofemoral (hip) joint:

1. Type

   • Synovial triaxial ball and socket joint

     • flexion, extension, abduction, adduction, medial rotation, lateral rotation
       

2. Articulation

   • Between hemispherical head of the femur and the lunate surface of the deep acetabulum formed by the ischium, ilium, and pubis bones

   • The cavity of the acetabulum is deepened by the acetabular labrum

3. Synovial Membrane

   • A synovial membrane lines the capsule and is attached to the articular surfaces

   • Synovial fluid is produced to keep the joint well articulated

   • This membrane extends to cover the neck of the femur and reflects onto the fibrous membrane

4. Capsule

   • The joint is enclosed by the fibrous capsule which attaches proximally to the acetabular labrum and distally to the intertrochanteric line (anteriorly) and the intertrochanteric crest (posteriorly)

5. Cartilage

   • Its articular surfaces are covered by hyaline cartilage (except fovea on the femoral head as the ligament of the femoral head attaches here)

6. Stability

   • Highly stable joint as two thirds of the head of the femur fit into the deep acetabulum and its labrum

Tibiofemoral (Knee) Joint

The following are some notes on the tibiofemoral (knee) joint:

1. Type

   • Femorotibial articulation - synovial modified hinge joint

   • Femoropatellar articulation - plane joint
     

2. Articulation

   • Between the lateral and medial femoral condyle and the lateral and medial tibial condyle

   • Between the patella surface of the distal femur and patella
     

3. Synovial Membrane

   • A common synovial membrane lines the capsule and is attached to the articular surfaces as well as the superior and inferior outer margins of the menisci

   • Synovial fluid is produced to keep the joint well articulated

   • Separated from the patellar ligament by infrapatellar fatty pad
     

4. Capsule

   • A fibrous capsule encloses the joint
     

5. Cartilage

   • Its articular surfaces are covered by hyaline cartilage
     

6. Menisci

   • 2 (one lateral and one medial) C-shaped fibrocartilage plates that aid the congruency between the femoral and tibial condyles by deepening the articular surface of tibial condyles to receive the femoral condyles

   • Superiorly the surfaces are in contact with the tibial condyles while distally they are attached to facets in the intercondylar region of the tibial plateau

   • The medial meniscus is attached to the joint and the ligament
     

7. Bursa

   • The bursa help to reduce the friction between the moving surfaces and they include:

     • Suprapatellar - between the distal end of the femur and the tendon of the quadriceps femoris muscle

     • Prepatellar - between the skin and patella

     • Superficial infrapatellar - between the skin and patellar ligament

     • Deep infrapatellar - between the patellar ligament and the tibia
       

8. Locking and Unlocking of the knees:

   • The knee locks when the weightbearing knee is fully extended and medial rotation of the femur occurs on the tibia (lateral rotation of the tibia on the femur)

   • This makes the joint more stable, allowing the thigh and leg muscles to relax

   • The knee unlocks when the popliteus muscle contacts therefore rotating the femur laterally on a fixed tibia

Clinical Notes:

1. Infrapatellar bursitis - this occurs when there is inflammation in the region due to friction between the skin and tibial tuberosity

2. Patellar bursitis - this occurs where there is inflammation in the region due to friction between the skin and patella

3. Lateral collateral ligament injury - this occurs when there is forced adduction of the tibia which in turn tears the lateral collateral ligament

4. Medial collateral ligament injury - this occurs when there is forced abduction of the tibia which in turn tears the medial collateral ligament

5. Anterior cruciate ligament tear - this occurs where there is hyperextension which in turn tears the anterior cruciate ligament

Talocrural (Ankle) Joint

The following are some notes on the talocrural (ankle) joint:

1. Type

   • Synovial hinge joint
     

2. Articulation

   • Superiorly - the mortise (rectangular socket) is formed by a deep bracket-shaped socket of the inferior tibia, medial malleolus of the tibia and the lateral malleolus of the fibular

   • Inferiorly - articular superficial talar end

3. Synovial Membrane

   • A synovia membrane lines the capsule and is attached to the articular surfaces

   • Synovial fluid is produced to keep the joint well articulated
     

4. Capsule

   • A fibrous capsules encloses the joint
     

5. Cartilage

   • Its articular surfaces are covered by hyaline cartilage

Subtalar (talocalcaneal) Joint:

The following are some notes on the subtalar (talocalcaneal) joint:

1. Type

   • Synovial plane joint
     

2. Articulation

   • Distally - corresponding talar facet on the superior calcaneal surface

   • Proximally - large posterior facet on the inferior talar surface

3. Synovial Membrane

   • A synovia membrane lines the capsule and is attached to the articular surfaces

   • Synovial fluid is produced to keep the joint well articulated
     

4. Capsule

   • A fibrous capsules encloses the joint
     

5. Cartilage

   • Its articular surfaces are covered by hyaline cartilage