Joints Flashcards
Ligaments stabilising the wrist
Palmar radiocarpal - It is found on the palmar (anterior) side of the hand. It passes from the radius to both rows of carpal bones. Its function, apart from increasing stability, is to ensure that the hand follows the forearm during supination.
Dorsal radiocarpal - It is found on the dorsum (posterior) side of the hand. It passes from the radius to both rows of carpal bones. It contributes to the stability of the wrist, but also ensures that the hand follows the forearm during pronation.
Ulnar collateral - Runs from the ulnar styloid process to the triquetrum and pisiform. Works in union with the other collateral ligament to prevent excessive lateral joint displacement.
Radial collateral - Runs from the radial styloid process to the scaphoid and trapezium. Works in union with the other collateral ligament to prevent excessive lateral joint displacement.
Ligaments stabilising the shoulder
Glenohumeral ligaments (superior, middle and inferior) – Consists of three bands, which runs with the joint capsule from the glenoid fossa to the anatomical neck of the humerus. They act to stablise the anterior aspect of the joint.
Coroacohumeral ligament – Attaches the base of the coracoid process to the greater tubercle of the humerus. It supports the superior part of the joint capsule.
Transverse humeral ligament – Spans the distance between the two tubercles of the humerus. It holds the tendon of the long head of the biceps in the intertubecular groove.
The other major ligament is the coracoacromial ligament. Unlike the others, it is not a thickening of the joint capsule. It runs between the acromion and coracoid process of the scapula, forming the coraco-acromial arch. This structure overlies the shoulder joint, preventing superior displacement of the humeral head.
Factors stabilising the elbow joint
Like all synovial joints, the elbow joint has a capsule enclosing the joint. This in itself is strong and fibrous, strengthening the joint. The joint capsule is thickened medially and laterally to form collateral ligaments, which stablise the flexing and extending motion of the arm.
The radial collateral ligament is found on the lateral side of the joint, extending from the lateral epicondyle, and blending with the anular ligament of the radius (a ligament from the proximal radioulnar joint).
The ulnar collateral ligament originates from the medial epicondyle, and attaches to the coronoid process and olecrannon of the ulna.
Interosseous membrane
sheet of connective tissue that joins the radius and ulna together between the radioulnar joints.
It spans the distance between the medial radial border, and the lateral ulnar border. There are small holes in the sheet, as a conduit for the forearm vasculature.
This connective tissue sheet has three major functions:
Holds the radius and ulna together during pronation and supination of the forearm, providing addition stability.
Acts as a site of attachment for muscles in the anterior and posterior compartments of the forearm.
Transfers forces from the radius to the ulna.
Factors stabilising the shoulder joint
Mobility
Stability
Factors that contribute to mobility:
Type of joint - It is a ball and socket joint.
Bony surfaces – Shallow glenoid cavity and large humeral head – there is a 1:4 disproportion in surfaces. A commonly used analogy is the golf ball and tee.
Laxity of the joint capsule.
Factors that contribute to stability:
Rotator cuff muscles – These muscles surround the shoulder joint, attaching to the tubercles of the humerus, whilst also fusing with the joint capsule. The resting tone of these muscles act to ‘pull’ the humeral head into the glenoid cavity.
Glenoid labrum: This is a fibrocartilaginous ridge surrounding the glenoid cavity. It deepens the cavity, reducing the risk of dislocation.
Ligaments – The ligaments act to reinforce the joint capsule, and forms the coraco-acromial arch.
Ligaments that strengthen joints in vertebrae
The joints between the articular facets are called facet joints. These allow for some gliding motions between the vertebrae. They are strengthened by various ligaments:
Ligamentum Flavum: extends from lamina to lamina.
Interspinous and Supraspinous ligaments: These join the spinous processes together. The interspinous ligaments attach between processes, and the supraspinous ligaments attach to the tips.
Intertransverse ligaments: extends between transverse processes.
Factors that stabilise the hip joint
acetabulum: deep, and encompasses nearly all of the head of the femur. This decreases the probability of the head slipping out of the acetabulum, and causing a dislocation.
acetabular labrum: fibrocartilaginous collar around the acetabulum which increases its depth. The increase is depth provides a large articular surface , thus improving the stability of the joint.
Ligaments: iliofemoral, pubofemoral and ischiofemoral ligaments are very strong, and along with the thickened joint capsule, they stabilise the joint greatly. These ligaments have a unique spiral orientation; this causes them to become tighter when the joint is extended, which adds stability to the joint, and also means less energy is needed to maintain a standing position.
Muscles and ligaments work in a reciprocal fashion at the hip joint:
Anteriorly, where the ligaments are strongest, the medial flexors (located anteriorly) are fewer and weaker.
Posteriorly, where the ligaments are weakest, the medial rotators are greater in number and stronger – they effectively ‘pull’ the head of the femur into the acetabulum.
3 main extracapsular ligaments of the hip
& their function
Iliofemoral ligament: prevents hyperextension of the hip during standing (screwing the head of the femur into acetabulum)
Pubofemoral ligament: prevent excessive abduction
Ischiofemoral ligament: prevent hyperextension (screwing the head of femur into acetabulum)
Ligaments of the knee
Extrinsic:
1. Patellar ligament – A continuation of the quadriceps femoris tendon distal to the patella. It attaches to the tibial tuberosity.
- Collateral ligaments - These are two strap-like ligaments. They act to stablise the hinge motion of the knee, preventing any medial or lateral movement
Tibial (medial) collateral ligament – A wide and flat ligament, found on the medial side of the joint. Proximally, it attaches to the medial epicondyle of the femur, distally it attaches to the medal surface of the tibia.
Fibular (lateral) collateral ligament – Thinner and rounder than the tibial collateral, this attaches proximally to the lateral epicondyle of the femur, distally it attaches to a depression on the lateral surface of the fibular head.
Internal:
3. Cruciate Ligaments - These two ligaments connect the femur and the tibia. In doing so, they cross each other, hence the term ‘cruciate’ (latin for like a cross)
Anterior cruciate ligament – attaches at the anterior intercondylar region of the tibia and ascends posteriorly to attach to the femur, in the intercondylar fossa. It prevents anterior dislocation of the tibia onto the femur.
Posterior cruciate ligament - attaches at the posterior intercondylar region of the tibia, and ascends anteriorly to attach to the femur in the intercondylar fossa. It prevents posterior dislocation of the tibia onto the femur.
