Joints of the Lower Limb Flashcards
Joints can be classified based on two criteria. What are they?
Structure (what unites the bones in a joint) and mobility
What are the Joint Classifications based on structure?
- Fibrous joints: are united by fibrous connective tissue (e.g., suture, superior tibiofibular joint) and the degree of mobility varies
- Cartilaginous joints: are united by hyaline cartilage (e.g., 1st sternocostal joint) or fibrocartilage (e.g., pubic symphysis) and the degree of mobility is limited
- Synovial joints: united by a complex joint capsule; this is the most common type of joint in the human body and they are highly mobile
What components do all synovial joints have?
- Synovial cartilage
- Joint capsule
- Joint cavity
What are the variable structures found in synovial joints?
- Bursae
- Tendon sheaths
- Fibrocartilage structures (i.e. Articular disc, Meniscus, Labrum)
- Ligaments (Extracapsular, Capsular, Intracapsular)
Describe Synovial cartilage
-A thin layer of hyaline cartilage covering each bone in the joint; unlike a cartilaginous joint, each bone in a synovial joint has a separate piece of cartilage covering it; in a normally functioning synovial joint, cartilage moves past cartilage; there is no direct bone to bone contact; synovial cartilage reduces friction between bones
Describe a Joint capsule
- Surrounds the articulating bones and consists of two layers
1) Fibrous layer: superficial layer; tough and fibrous; protects remainder of joint
2) Synovium: inner layer facing joint cavity; secretes synovial fluid
Describe a Joint cavity
-Potential space defined by joint capsule; filled with a small amount of fluid called synovial fluid, which provides lubrication and nutrition to the contents of the joint capsule
Describe Bursae
-Synovial structures with fibrous layer, synovium, and synovial fluid filled cavity cavity; may or may not be in communication with the main joint capsule; facilitate movements of structures that cross a joint
Describe Tendon sheaths
-Specialized bursae that wrap around tendons crossing the writs and ankle to facilitate tendon movements
What are the Fibrocartilage structures?
- Articular disc: fibrocartilage pad between bones in a joint
- Meniscus: C-shaped disc between bones in a joint
- Labrum: rim of cartilage surrounding the articular margin of one bone in a joint
Describe Ligaments
-Bands of connective tissue crossing a joint; classified based on their relationships to the joint capsule
What are the types of ligaments?
- Extracapsular: outside the joint capsule
- Capsular: thickening of the joint capsule
- Intracapsular: inside the joint capsule
What are the Joints of the Lower Extremities?
Sacroiliac Joint Hip Joint Knee Joint Tibiofibular joints Talocrural and Subtalar joints Arches and Ligaments of the Foot Metatarsaophalangeal joints Interphalangeal joints
Describe the Sacroiliac Joint
- Compound joint: partly fibrous and partly synovial; becomes more fibrous with age
- Strengthened by ligaments (almost all of body weight is transmitted from the sacrum to the ilium, so it needs to be strong):
1) Intrinsic ligaments (restricted to the area around the joint)
- Anterior sacroiliac ligament
- Posterior sacroiliac ligament
2) Extrinsic ligaments: counteract turning moment produced by the fact that the body’s center of mass is anterior to the SI joint
- Sacrotuberous ligament
- Sacrospinous ligament
Describe the Hip joint and what ligaments are associated with it
- Ball and socket joint: potentially very mobile and unstable
- Strengthened by a cuff of capsular ligaments
- Iliofemoral and ischiofemoral ligaments become tight in extension to prevent hyperextension
- Pubofemoral ligament becomes tight in abduction to prevent hyperabduction
Describe how the acetabulum and the femoral head interact at the Hip Joint
1) Acetabulum
- Articular surface is C-shaped lunate surface, open ventromedially by acetabular notch
- Margin of acetabulum is extended by a fibrocartilage labrum
2) Femoral head
- Ball shaped surface with a small depression, the fovea capitis, which serves as a point of attachment of the round ligament, which weakly holds the femoral head against the acetabulum
Describe blood supply to the hip
- Lateral circumflex femoral a. femoral shaft
- Medial circumflex femoral a.: primary blood supply to the femoral head and neck
- Acetabular branch of the obturator a.: runs in round ligament, supplies head and neck, but not always sufficient on its own
-Hip fracture (fracture of femoral neck) can disrupt the blood supply to the femoral head/neck; if acetabular branch is insufficient, this can result in avascular necrosis of the head and neck
Describe the knee joint
- Relatively unstable hinge joint between convex femoral and flat tibial condyles
- Patellofemoral joint: between patella and femur; patella slides back and forth in patellar groove
What are the menisci of the knee joint?
-Medial and lateral menisci improve the contact between femur and tibia, making joint more stable
What are the ligament of the Knee joint?
- Lateral collateral ligament (LCL): extracapsular ligament; prevents lateral bowing of knee
- Medial collateral ligament (MCL): capsular ligament; attached to medial meniscus; prevents medial bowing of knee
- Anterior cruciate ligament (ACL): origin anterior on tibia; inserts posteriorly on femur; intracapsular ligament; prevents hyperextension
- Posterior cruciate ligament (PCL): origin posterior on tibia; inserts anteriorly on femur; intracapsular ligament; prevents hyperflexion
-“Unhappy triad injury”: lateral force applied to the knee with the foot planted and the knee extended can produce hyperextension and medial bowing, tearing the 1) ACL, 2) MCL, 3) medial meniscus where it is attached to the MCL
Describe the Tibiofibular joints
- Two joints between tibia and fibula
1) Proximal joint is synovial (superior tibiofibular joint)
2) Distal joint is fibrous (inferior tibiofibular joint) - Little movement possible
Describe the Talocrucal joint
- A hinge synovial joint between distal tibia and lateral malleolus of distal fibula proximally, talus distally
- Range of motion: dorsiflexion/plantarflexion
Describe the Subtalar joint
- A synovial joint between the talus and calcaneus
- Range of motion: inversion/eversion
What are the Associate ligaments of the Talocrural and Subtalar joints
- Medial collateral (deltoid) ligament: 4 parts; prevents hypereversion
1) Tibionavicular ligament
2) Tibiocalcaneal ligament
3) Anterior tibiotalar
4) Posterior tibiotalar - Lateral collateral ligament: 3 parts; prevents hyperinversion
1) Anterior talofibular
2) Posterior talofibular
3) Calcaneofibular
