Q3- Describe The Structure Flashcards
Glenohumeral joint
This joint is a synovial ball and socket joint located between the humerus and scapula which has three degrees of freedom of movement. It sacrifices stability to allow mobility. The Glenoid cavity is very shallow and relies on the Glenoid labrum which arises from the margins of the acetabulum to provide more depth to the socket. The joint capsule attaches from the labrum and inserts towards the anatomical neck of the humerus, therefore providing some stability. The capsule is crossed by three ligaments anteriorly and two ligaments superiorly to support the joint. The superior, middle and inferior glenohumeral ligaments limit excessive extension, lateral rotation and abduction. The coracohumeral ligament and coracoacromial ligament limit excessive depression of the humerus. The rotator cuff muses provide dynamic stability to the joint, they keep the ball in the socket and rotate the humerus. The supraspinatus Abducts the humerus, the infraspinatus laterally rotates the humerus, the subscapularis medially rotates the humerus and the teres minor laterally rotates the humerus.
Elbow
The elbow is a compound synovial joint. The articulating bones are the humerus, radius and ulna. The humero-radial articulation is between the capitulum and the head of the radius. The humero-ulna articulation is between the trochlear and the trochlear notch of the ulna. The joint capsule is a fibrous membrane covering the synovial membrane to enclose the joint. It attaches to the margins of the epicondyles, the neck of the radius, the olecranon and the coronoid process of the ulna. The joint capsule is strengthened by the radial and ulnar collateral ligaments. The radial collateral ligament proximally attaches to the lateral epicondyle of the humerus and distally attaches to the annular ligament. The ulnar collateral ligament proximally attaches to the medial epicondyle of the humerus and distally attaches to the medial aspect of the olecranon. The ulna collateral ligament stabilises the medial aspect of the elbow and prevents abduction of the forearm. The radial collateral ligament stabilises the lateral aspect of the elbow and prevents Adduction of the forearm. The annular ligament encircles the head of the radius and hugs it to the radial notch of the ulna. The quadrate ligament limits spin of the radial head upon the ulna and limits supination and pronation. Between the radius and ulna is interosseous membrane which transmits force from the hand provides an area for muscle attachment.
Talocrural joint
The ankle joint is a synovial hinge joint connected by the distal ends of the tibia and fibula and the body of the talus. It has one degree of freedom of movement which is plantar flexion and dorsiflexion. The closed pack position of the ankle is full dorsiflexion. The head of the talus is wider than the gap between the distal ends of the tibia and fibula, so during dorsiflexion the fibula undertakes it’s own accessory movement by slightly laterally rotating to widen the gap so the talus can fit into it during dorsiflexion. The joint capsule of the ankle is thin and doesn’t offer much stability so the stabilising ligaments provide more stability. The medial collateral ligament attaches from the medial malleolus to the calcaneus and limits eversion of the foot, therefore limting eversion sprains. The lateral collateral ligament is composed of the anterior talo-fibular ligament, posterior talo-fibular ligament and calcaneo-fibular ligament. All three proximally attach to the lateral malleolus and the talo-fibular ligaments attach to the talus and the calcaneo ligament attaches to the calcaneus. The LCL limits inversion of the foot so limits inversion sprains. Inversion sprains are more common because the LCL is the only like of defence whereas eversion sprains are uncommon because the fibula extends distally and blocks the foot from moving to that side during eversion. The retinacula of the joint is located anteriorly and posteriorly,and holds down the tendons crossing the ankle joint to prevent bow stringing of the tendons
Knee joint
The knee is the largest synovial joint in the body and is a bi-axial hinge joint. It is more than a hinge joint because the knee allows rotation of the tibia upon the femur. The Tibial surface of the knee is concave but very shallow so the knee requires two menisci to provide depth to the femoral condyles. The medial femoral condyle is longer than the lateral femoral condyle so during flexion and extension the lateral condyle stops before the medial condyle which causes the rotation component. This is called the screw home mechanism and is important for knee extension. As the Tibial surface is concave, the quadriceps pull the tibia forwards and the hamstrings pull the tibia backwards. The anterior cruciate ligament prevents the tibia from sliding too far forwards and the posterior cruciate ligament restricts posterior movement of the tibia relative to the femur. The ACL arises from the intercondylar area of the tibia, ascends posterolaterally and inserts into the lateral wall of the intercondylar fossa. The PCL arises from the posterior intercondylar area of the tibia, ascends anteromedially and inserts into the medial wall of the intercondylar fossa. The medial collateral ligament prevents excessive abduction of the tibia and the lateral collateral ligament prevents excessive adduction of the tibia. The MCL proximally attaches to the medial epicondyle of the femur, just inferior to the adductor tubercle, and distally attaches to the medial aspect of the tibia. The LCL proximally attaches to the lateral epicondyle of the femur and distally attaches to the lateral surface of the head of the fibula. The joint capsule of the knee is a thick ligamentous sheath. It anteriorly blends with the patella and quadriceps insertions, medially blends with the MCL and medial meniscus and laterally blends with the iliotibial band.
The hip
The hip is a synovial multiaxial ball and socket joint. It provides stable weight transference. It’s articular surfaces are reciprocally curved to provide a secure articulation but the surfaces are not fully congruent as the head is larger than the socket. The synovial joint capsule is strong and reinforced by ligaments. The iliofemoral ligament and pubofemoral ligament are anterior whereas the ischiofemoral ligament is posterior. All three limit hip extension, but the iliofemoral and pubofemoral limit lateral rotation and abduction whereas the ischiofemoral limits medial rotation and Adduction. The iliofemoral arises from the anterior inferior iliac spine and fans out to attach along the intertrochanteric line. The pubofemoral superiorly attaches to the superior pubic ramus and inserts laterally to the trochanteric fossa. The ischiofemoral arises from the ischium and posterior labrum and inserts laterally into the greater trochanter.
Proximal radioulnar joint
This joint is a synovial uniaxial pivot joint between the head of the radius and the radial notch of the ulna. The annular ligament encircles the head of the radius and hugs it to the radial notch of the ulna, therefore helping stabilize the joint. It has one degree of freedom of movement, which is pronation and supination. During pronation, the radius medially rotates relative to the ulna and during supination the radius laterally rotates relative to the ulna. The joint capsule is continuous with the elbow joint so shares the same joint capsule.
Distal radioulnar joint
This joint is a synovial uniaxial pivot joint between the head of the ulna and the ulna notch of the radius. It has one degree of freedom of movement which is pronation and supination. The capsule is a loose fibrous capsule. The radioulnar disc runs from the distal radius to be distal ulna and stabilizes the joint.
Patella-femoral joint
This is a synovial plane joint. On the posterior surface of the patella is smooth medial and lateral facets which articulate with the femoral condyles. The patella is most stable when the knee joint is in flexion. The articular surface of the patella has the thickest cartilage of any in the body to withstand the compressive force of the patella against the femur.
Subtalar joint
This is a synovial plane joint between the concave inferior surface of the talus and convex superior aspect of the calcaneus. It allows inversion and eversion of the foot. The capsule is a fibrous joint capsule. The medial talocalcaneal ligament is from the medial tubercle of the posterior process of the talus to the posterior surface of the sustentaculum tali. The lateral talocalcaneal ligament is from the lateral process of the talus to the medial surface of the calcaneus. These ligaments help stabilize the joint. The interosseous talo-calcaneal ligament lies within the sinus tarsi and limits eversion. The spring ligament attaches from the calcaneus to Navicular bone and limits eversion.
Wrist complex
The radiocarpal joint is a compound joint located between the distal end of the radius and the proximal row of carpal bones. The ulna does not directly articulate with carpal bones but the ulnocarpal joint does transmit 20% of the load from the hand to the forearm. The radiocarpal joint shares the same joint capsule with the distal radioulnar joint. The midcarpal joint is a compound joint located between the proximal row of carpal bones and the distal row of carpal bones. The transverse carpal ligament forms the roof of the carpal tunnel and it’s function is to stabilize the carpal tunnel. The dorsal radiocarpal ligament is located on the dorsal side of the radius to the carpal bones and limits full flexion. The palmar radiocarpal ligaments are located on the palmar side of the radius to the carpal bones and they limit full extension. The radial collateral ligament is located from the styloid process of the radius to the Schaphoid and Trapezium and limits ulnar deviation. The ulnar collateral ligament is located from the styloid process on the ulna to the Triquetrum and limits radial deviation.
The 1st carpometacarpal joint of the thumb
The first carpometacarpal joint is a synovial saddle joint located between the Trapezium and the base of the first metacarpal. This is the most mobile of the carpometacarpal joints, it allows flexion, extension, Adduction, Abduction, medial and lateral rotation. The joint is stabilised by a fibrous joint capsule and carpometacarpal ligaments. However the capsule is loose therefore allowing large ranges of motion. These are the radial and ulnar collateral ligaments, the anterior and posterior oblique ligaments and the first intermetacarpal ligament. The ligaments generally become taut in full abduction or extension. The flexor pollicis longus, Extensor pollicis longus and brevis, and abductor pollicis longus, and thenar eminence are the major muscles.
