Topic 6- Joints

Question 1

What is the structure and function of joints?

Answer 1

Joints allow the body to move under the action of muscles so that we can initiate movement and react to the environment around us. Joints are where two or more bones articulate (meet)

Question 2

What can affect the stability, movement and strength of a joint?

Answer 2

The shape and strength of the bones and the flexibility and strength of the muscles and other tissues surrounding the joint.

Question 3

What are the three different types of joints?

Answer 3

• Fibrous
• Cartilaginous
• Synovial

Question 4

Describe and give examles of a fibrous joint.

Answer 4

The bony surfaces of the joints are united by fibrous tissue and are tight fitting. These joints do not move and there is no joint cavity. Examples of this type of joint includethe skull structures.

Question 5

Describe and give examles of a cartilaginous joint.

Answer 5

The bony surfaces of the joints are connected by hyaline cartilage and there is some flexibility within the joint but no joint cavity. Examples of cartilaginous joints include in the intervertebral discs of the backbone.

Question 6

Describe and give examles of a synovial joint.

Answer 6

The bony surfaces of these joints are covered with hyaline cartilage and are enclosed in a fibrous capsule or synovium. This allows free movement of the joint within a fixed range. Examples include the hip, knee, shoulder and elbow joints.

Question 7

How does the shape and contour of the articulating surfaces affect the range of movement at a joint?

Answer 7

Bones with a curved surface that fit together closely form strong joints. Movement at this type of joint is limited. Bones that have less of a curved surface and do not fit together so closely form a less stable joint. Movement at this type of joint is greater.

Question 8

How does the capsule (synovium) and ligaments surrounding the joint affect the range of movement at a joint?

Answer 8

The synovium and ligaments support and stabilise the joint. They prevent abnormal movements of the joint. Ligaments consist of tough, non-elastic fibrous tissue and join bones together. If ligaments are subject to a great force, they may tear; partial tears result in sprains and complete tears may cause the joint to dislocate.

Question 9

How does the muscle and tendons around the joint affect the range of movement at a joint?

Answer 9

Muscles that are more elastic following warming up will allow a greater movement of the joint compared to tighter muscles. Forcing a joint when the muscles are not warmed up may result in tears.

Question 10

How does proximity of soft tissues near the joint affect the range of movement at a joint?

Answer 10

The movement of a joint is limited when two surfaces touch each other. For example, complete bending of the joint at the knee will be limited by the size of the muscles and the amount of body fat surrounding the back of the thigh and calf.

Question 11

How does age affect the range of movement at a joint?

Answer 11

Tissues and ligaments tighten with increasing age. This can be counter balanced with good regular exercise.

Question 12

How does hypermobility affect joints?

Answer 12

People who are ‘double jointed’ (hypermobile) they have a greater range of movements because they have lax ligaments. The downside of this is that the joints tend to be less stable. Therefore they need to develop stronger muscles to help support their joints.

Question 14

What is cartilage?

Answer 14

Cartilage is a tissue that is made up of cells, chondrocytes and fibres embedded in a gel-like matrix which is responsible for the strength and resilience of the tissue.

Question 15

How does the gel-like matrix (part of cartilage) work?

Answer 15

It is made up of substances called mucoproteins, comprising of proteins and glycogen which have a great capacity to hold water. The water is then squeezed out of the cartilage into the joint space to facilitate lubrication. This water is then reabsorbed when the load is reduced.

Question 16

What are the two types of cartilage that are important to dancers?

Answer 16

• Hyaline
• Fibrocartilage

Question 17

What is hyaline cartilage and how does it work?

Answer 17

This type of cartilage is found at the end of long bones within the synovial joints. The cartilage covers the weight-bearing ends of the bone to protect them from the effects of stress. Hyaline cartilage provides a smooth, slippery, firm surface in the joint and is three times as slippery as smooth ice. Hyaline cartilage increases in thickness in response to regular exercise. This improves the cushioning properties of cartilage and so protects the joint from high impact activities.

Question 18

What is fibrocartilage and how does it work?

Answer 18

Found in the intevertabral discs of the spine, the rib cage and in the knee joint. This type of cartilage contains fibrous bundles and fewer cells than hyaline cartilage. In the knee joint, the fibrocartilage is disc-shaped (menisci) and is attached to the bone to provide a better fit and cushion the joint movement.

Question 19

What is the effect if the cartilage is damaged?

Answer 19

Damage to cartilage results in increased friction within the joint as bone moves over bone causing stiffness and pain. Due to the poor blood and nerve supply, cartilage has a low metabolic rate. As a result the capacity for repair is poor and any injury may be permanent. Generally cartilage is replaced with fibrous tissue once damage has occurred. Fibrous tissue doesn’t have the same properties as cartilage.

Question 20

What are ligaments?

Answer 20

Ligaments are bands of tissue that connect two bones and prevent excessive movement in a joint, providing stability.

Question 21

How do ligaments get damaged? How can they be repaired?

Answer 21

Ligaments get damaged when they are forced into abnormal positions. Torn ligaments cause pain and swelling of the affected area and may result in the joint becoming unstable. Complete tears of ligament fibres may require an operation to stitch the ligament back together. It is usual for the joint to be immobilised and initial healing can take 6-12 week. A period of rehabilitation will also be essential to facilitate return to both normal activity and dance.

Question 22

True or false?

Ligaments increase in strength in response to regular exercise

Answer 22

True!

This improves the capacity to withstand excessive forces that are applied to joints.

Question 24

Describe the role and function of the synovium.

Answer 24

A delicate synovial membrane covers the surfaces of the synovial joint. Synovial fluid is contained within the tissues of this membrane. Synovial fluid is present in joints at all times, althogh more may be secreted into the joint capsule when a high load is applied. The synovial fluid lubricates the joint and together with the fluid released from hyaline cartilage provides a friction free surface to the interior of the joint. The secretion of synovial fluid increases following regular exercise, improvng lubrication and joint function.

Question 25

Many dancers complain of ‘clicky joints’, what does this mean and what should dance teachers be aware of?

Answer 25

It is not always a problem to experience this as joints often click dring normal everyday activity. If these clicks hurt, there is an indication that something maybe wrong.

Dance teachers need to be aware that people who are new to dance or people who increase the number of hours practising can often experience clicky joints. In these cases, it is important to start or increase strengthening exercises.

Question 26

What are bursae?

Answer 26

Pockets or sacs of synovial membrane that lie between tendons or muscle and bone. The function of bursae is to reduce excessive friction where muscles or tendons cross a joint much in the same way as in a synovial joint. Bursae are most commonly found surrounding the knee joint and in the heel.

Question 27

What is meant by the term bursitis? What causes it? How can it be treated?

Answer 27

Bursitis is a condition when bursae become inflamed following injury or repetitive movements and resullt in swelling, stiffness and pain. Treatment initially involves rest and if the inflamation does not settle, may involve a cortisone injection.

Question 28

What causes swollen joints?

Answer 28

A swollen joint is due to inflamed synovial membranes caused by injury and illness. The typical disease that causes joint swelling and stiffness and eventually leads to the destruction of adjoining bones, cartilage, ligaments and tenons. Although this condition usually affects older people, there are juvenile forms of the condition that are just as debilitating.

Question 29

What is acute synovitis and how can it be treated?

Answer 29

Acute synovitis is an acute reaction of the synovial membrane to injuries affecting the joint. The synovial fluid secretes a fluid that does not have the lubricating properties of the normal synovial fluid. This results in swelling of the joint and movement becomes restricted.

Treatment of acute synovitis requires the person to res the joint for at least 48 hours. This is sufficient as repair occurs rapidly due to the rich blood supply of the synovial membrane. Repair of the surrounding tissue, such as muscles, will take longer.

Question 30

What is osteoarthritis?

Answer 30

This is a condition where degenerative changes occur in a joint and is common in older people. The hip, kneed and spine are generally affected. Although the causes are not clear, the condition is more common in dancers and athletes. This is thought to be due to the chronic wear and tear on the joints and the effects of old injuries. The common symptoms are pain and stiffness of the joints made worse by activity and improved upon resting.

Question 31

What happens to the cartilage in someone with osteoarthritis?

Answer 31

The cartilage surrounding the affected bones is destroyed leaving unprotected bone surfaces to articulate with one another, the capsle becomes fibrotic and small growths occur at the ends of bones. This causes pain and restricts joint movement.

Question 32

How can physio help people with osteoarthritis?

Answer 32

Treatment is aimed at strengthening the muscles surrounding the joint, which, when stronger,can support the damaged joint better, thus relieving pain and allowing further exercise. Another common therapy is acupuncture which can help relieve the pain and swelling. Low impact exercise is crucial for people with osteoarthritis.

Question 33

Why is it important for dance teachers to consider whilst teaching dance to older people, that some of them may have had hip or knee replacements?

Answer 33

Hip and knee replacements are prone to dislocation if the limb movements are sudden and require a high degree of flexibility across the joint. The teacher should therefore ask older people if they have had these surgical procedures and, if that is the case, modify the steps or movements they plan to use in their classes accordingly.