The musculoskeletal system

4.2 The musculoskeletal system



Chapter 4.2a The physiology of the musculoskeletal system



Learning points



At the end of this chapter you will be able to:


• describe the structure and function of the different types of bones

• describe the different types of joints and their functions

• describe how the skeletal muscles act to maintain posture and allow movement.

Estimated time for chapter: 120 minutes.



Introduction


The musculoskeletal system consists of the bony skeleton, the joints and the muscles. Its functions are to support the soft tissues of the body, to protect the deep organs and to enable the movements of the body. In addition, as described in Stage 3, the bones contain the marrow spaces in which most of the maturation of the blood cells takes place.


This chapter considers in turn the physiology of the bony skeleton, the joints and the muscles. It is assumed that the reader has a basic knowledge of the shape, position and names of the bones, joints and muscles.



The physiology of the bony skeleton


All bone consists of a combination of a hard, non-living substance containing salts of calcium and phosphorus together with a vast number of living bone cells. The non-living part of bone is structured upon a scaffolding of numerous connective-tissue fibres. It is this complex material that persists after death when the rest of the body has decayed. Nevertheless, in life, this seemingly fixed aspect of bone is constantly in a state of change, as the bone cells are always active in reshaping this hard material according to the needs of the body.


There are two main types of bone tissue. Compact bone is a dense, but very strong material present in all bones at their margins. Cancellous bone is more spongy and filled with red marrow, and is particularly rich in the shafts of the long bones and the ribs, the centre of the vertebral bodies and the core of the pelvic bones. In both types of bone a rich network of vessels supplies the bone cells, the osteocytes, with blood and lymph fluid.


The bony skeleton is made up of four different types of bones, categorised according to their shape: the long bones (e.g. the femur and the humerus), the irregular bones (e.g. the vertebrae and the carpal bones), the flat bones (e.g. the sternum and the skull) and the sesamoid bones (e.g. the patella and the pisiform bone). In terms of physiology, the important distinction to be made is between the long bones and the three other types of bone (irregular, flat and sesamoid) (see Q.4.2.a.1)image.



Long bones


The long bones (Figure 4.2a-I) in the body are the radius, ulna and humerus of the arm and the femur, tibia and fibula of the leg. They are characterised by a shaft and two widened ends known as ‘epiphyses’. The shaft is composed of dense, strong compact bone, with a central hollow that is filled with fatty yellow bone marrow. The epiphyses are the site of bone growth in the child, and are largely composed of soft, spongy cancellous bone containing bloody red marrow, all bounded by a rim of strong compact bone. The epiphyses are covered with hyaline cartilage in the regions where they make joints with other bones; elsewhere the long bones are bounded by a fibrous coat called the ‘periosteum’. Underneath the periosteum lie clusters of osteblasts and osteoclasts, the bone-forming cells that are responsible for bone remodelling and production. These cells are stimulated to form and reshape new bone when the periosteum or underlying bone becomes damaged. The design of the long bones confers strength, which is necessary for their main functions of locomotion, posture and manipulation.


image

Figure 4.2a-I • The structure of a long bone (partially sectioned).



Short, irregular, flat and sesamoid bones


The short bones are less strong than the long bones because they are composed largely of spongy, cancellous, red, marrow-containing bone, and are bounded by a relatively thin protective rim of compact bone. This structure (Figure 4.2a-II) supports their functions of intricate movements (in the back, hands and feet), protection (skull bones, pelvis and ribs) and bone marrow production (see Q4.2a-2)image.


image

Figure 4.2a-II • The structure of flat and irregular bones (sectioned).



The blood-forming marrow


It is the red marrow that is the site of the development of the blood cells. This marrow is abundant in the vertebrae and the flat bones of the skull, ribs, sternum and pelvis.



The growth of bone in childhood and adolescence


An understanding of how bones grow is relevant to the pathology of a number of the diseases of bone. In the fetus there is initially no hard bony material. Instead, at the future site of the long and irregular bones, soft cartilage, a form of connective tissue, appears. At the site of the flat bones a soft-tissue membrane develops. Gradually, as birth approaches, osteoblast cells within these areas of soft tissue secrete the hard substance that will form the non-living part of bone. This process of transformation of soft tissue into hard bone is called ‘ossification’. When bone has ossified, some of the osteoblasts mature into the bone cells situated deep within bone, where they are known as ‘osteocytes’.


This means that in the newborn only a small part of each of the bones is mature hard bone. For example, at the time of birth, only the centres of the skull bones have ossified. The edges of these flat bones are still thick membrane, which allows for some flexibility of movement between the skull bones (very important during childbirth). This soft membrane is most prominent in the diamond-shaped ‘soft-spot’ (the fontanelle) which can be felt on the top of the head of most babies under 1 year of age.


The bones do not fully ossify until early adulthood. Until then, there are still some areas of cartilage or membrane that are actively forming new bone and allowing for growth. Because of this, the approximate age of a child can be estimated from an X-ray image of the bones, which shows the state of progression of ossification of the bones. Puberty is a time during which the surge of sex hormones causes an initial spurt of growth of long bones followed by ossification of the growth centres in the long bones (see Chapter 5.2a). This is why growth slows considerably once puberty has been reached.



The continued growth of bones


After early adulthood the bones do not change significantly in size. Nevertheless, the osteoblasts remain active in secreting new bone. This laying down of new bone is counterbalanced by the activity of another type of bone cell called the ‘osteoclast’. The osteoclasts act continually to digest old bone and to return the calcium, phosphorus and other nutrients within the bone back to the circulation for reuse. This process, known as ‘remodelling’, allows bones to become stronger in areas in which there is perpetual physical stress (e.g. the upper part of the femur in someone who is physically active) and allows for the repair of bones in the case of fracture.


The rate of remodelling of bone is influenced by various hormones of the endocrine system. The thyroid hormones, growth hormone from the pituitary gland and insulin from the pancreas stimulate the correct development and ossification of the bones. In puberty, testosterone and oestrogen stimulate the growth spurt, and also the changes that differentiate the male and the female adult skeletons. Oestrogen also helps to maintain the calcium content of bones in premenopausal women. In addition, two hormones secreted from the region of the thyroid gland, calcitonin and parathyroid hormone, are essential in the control of the balance of the activity of the osteoblasts and the osteoclasts.


Vitamin D is an essential factor in the maintenance of the non-living (calcified) part of bone. In vitamin D deficiency the bones become softened. This leads to bowing of the bones during childhood (rickets) and pain and weakness in adulthood (osteomalacia). These conditions are discussed in more detail in Chapter 4.2d.



The structure of the skeleton


The skeleton can be considered as consisting of two parts: the axial skeleton and the appendicular skeleton. The axial skeleton (shaded bones in Figure 4.2a-III) forms the central bony core of the body, and consists of the skull, vertebral bones, sacrum, coccyx, ribs and sternum. All these bones are either flat or irregular, and so each is composed of a core of red-marrow-containing cancellous bone surrounded by a thin rim of compact bone. The skull and the vertebral column support and protect the fragile structure of the brain and spinal cord. The ribs and sternum likewise support and protect the lungs and the heart in the thorax, and the organs of the upper abdomen, including the liver, kidneys, pancreas and the spleen.


image

Figure 4.2a-III • The skeleton: anterior view (the bones of the axial skeleton are shaded).


The appendicular skeleton (unshaded bones in Figure 4.2a-III) is so called because it consists of the appendages to the axial skeleton. These are the shoulder girdle (clavicles and shoulder blades), the upper limbs, the pelvic girdle (the hip bones) and the lower limbs. The bones of the shoulder girdle and the pelvic girdle are flat bones. The bones of the limbs are either long bones or irregular bones.



The healing of bones


Healthy bones are strong and slightly flexible. In health, bones will only break if exposed to significant trauma. Fractures of healthy bone can be classified as simple, compound or green-stick. If a fracture occurs because the bone is weakened in some way by an underlying disease process, it is described as a ‘pathological fracture’.


A simple fracture describes when the ends of the bone do not protrude through the skin, whereas a compound fracture involves a break to the skin by the sharp end of the fractured bone. A greenstick fracture occurs in the flexible bones of young children. In this fracture, the break is incomplete, as the bone is far less brittle than the fully ossified adult bone. This means that the bone bends like a green stick, rather than snapping into two.


The healing of broken bones can be compared to the healing of wounds in that it is the formation of a blood clot in the space between the broken ends that initiates the healing process. Figure 4.2a-IV illustrates the stages in the healing of the broken shaft of a long bone. The blood clot stimulates the inward movement of phagocytes and osteoblasts. The phagocytes remove unwanted debris, while the osteoblasts lay down an initially chaotic mass of new bone called ‘callus’. The callus is gradually remodelled by osteoclasts into new, ordered compact bone. In adults this process takes weeks to months, but it is significantly quicker in children (see Q4.2a-3 and Q4.2a-4)image.


image

Figure 4.2a-IV • The stages in bone healing.



image Information Box 4.2a-I The bones: comments from a Chinese medicine perspective


In Chinese medicine, the bones and bone marrow have a relationship with two of the extraordinary Yang organs: the Bones and the Marrow.


The Marrow corresponds to the substance that nourishes and forms nervous tissue and the bone marrow, and which is produced by Kidney Essence. Therefore, if the Kidneys are deficient, the bone marrow will be weak.


The Bones correspond directly to the physiological bones. They are nourished by Kidney Essence and Marrow, and will also become weak if the Kidneys are deficient.



The physiology of the joints


The joints are the sites in the body at which two or more bones come together. They are essential for allowing free, but controlled, movement of the body (see Q4.2a-5)image.


There are three categories of joint in the body: the fixed or fibrous joints (e.g. the sutures of the skull), the slightly movable or cartilaginous joints (e.g. symphysis pubis and intervertebral joints) and the movable or synovial joints (e.g. the elbow, knee and ankle).


Fibrous joints involve two edges of bone that are linked by tough strands of fibrous connective tissue. The suture lines of the skull are an example of fibrous joints (Figure 4.2a-V). The movement at a fibrous joint is limited.


image

Figure 4.2a-V • An example of a fibrous joint: a suture line of the skull.


Cartilaginous joints offer the potential for more movement because the bones in these joints are linked by a pad of fibrocartilage, which has more spring and bulk than the fibrous strands of a fibrous joint. In the pubis symphysis and in between the vertebral bodies this fibrocartilage pad has a shock-absorbing function (Figure 4.2a-VI).


image

Figure 4.2a-VI • An example of a cartilaginous joint: the intervertebral joint.


Synovial joints offer the most movement and have the most complex structure (Figure 4.2a-VII). The internal surface of the bones in synovial joints is lined with glassy smooth hyaline articular cartilage, and the rest of the joint space is bound by a fibrous joint capsule (the capsular ligament). The internal surface of the joint is lined with a fluid-secreting synovial membrane. The term ‘synovial’ has its root in the Greek word ‘ovum’ meaning egg. This is because the lubricating fluid contained within these joints has been likened in consistency to the white of an egg. The whole joint is given stability by means of fibrous bands (the ligaments) that link the bones and also by the muscle insertions (the tendons), which cross the joint to insert close to its margins.


image

Figure 4.2a-VII • An example of a synovial joint: section of the knee joint viewed from the front.


Some of the synovial joints have unique additional features, for example the knee joint illustrated in Figure 4.2a-VII contains thickened C-shaped cartilage pads, which sit on the tibial plateau, and two cruciate (crossing) ligaments, which run through the joint space to provide anterior to posterior stability.


Close to the large joints such as the knee, hip and shoulder are fluid-filled sacs lined with synovial membrane called ‘bursae’ (singular ‘bursa’). The purpose of a bursa is to prevent friction between the layers of tissue overlying the joint.


There are a wide range of structures of synovial joints, although all have the same basic features listed above. Diverse examples include the ball-and-socket joint of the hip, the hinge mechanism of the elbow, the pivot provided by the atlantoaxial joint (between the C1 and C2 vertebrae) and the complementary saddle shapes of many of the small bones of the hands and feet (see Q4.2a-6-Q4.2a-7)image.



image Information Box 4.2a-II The joints: comments from a Chinese medicine perspective


The physiological joints are made up of bone, ligaments and synovial fluid, further supported by muscles. In this way their health is dependent on Kidney Essence, Liver Qi and Blood, and Gallbladder Qi, all of which are said to have direct correspondences with these aspects.


The fluid that lubricates the joints in Chinese medicine is called Ye, and is under the control of the Spleen and the Kidneys.



The physiology of the skeletal muscles


The muscles that are responsible for the movement of the bony joints are all largely composed of skeletal muscle fibres (cells). The muscle fibres run parallel to one another within each muscle, and are bound together by fibrous connective tissue. The muscle fibres converge at two or more fibrous structures, called ‘tendons’, at the extremities of the muscle. Tendons usually insert into a part of the bony skeleton, but in some muscles they attach to the connective tissue of the skin (e.g. in the muscles of facial expression). The fibrous tissue of muscles (including the tendons) is glistening white and contains blood vessels and fat cells. This is the tissue that gives a raw steak its streaky appearance (see Q4.2a-9)image.


The muscle fibres contract in unison in response to motor nerve impulses (see Chapter 4.1a). Each muscle fibre receives electrical impulses from a nerve fibre via a specialised synapse called the ‘motor end plate’. At this synapse, the electrical impulse travelling down the nerve fibre leads to the release of a neurotransmitter chemical. This chemical stimulates the changes within the muscle fibre that culminate in a temporary contraction. The contraction is sustained only for as long as the nerve continues to stimulate the motor end plate.


Muscles act because they are attached to at least two separate parts of the body, and because they can contract. When a muscle contracts, it draws the two or more parts of the body to which it is attached closer together, and this leads to movement.


Most skeletal muscles never attain a state of full relaxation. There is always a low level of nervous stimulation to the muscles, which gives them a firmness known as ‘tone’. This background level of tone is essential for correct posture. It is generated as a result of reflex nervous activity at the level of the spinal cord, and is modified further by nervous impulses originating from higher control centres in the brain (see Chapter 4.1a). If the nerve supply to a muscle is cut off, the muscle becomes completely flaccid, and loses the springy quality that is the normal state in good health.


Muscles act in a variety of ways, of which the biceps brachii, the buccinator and the pelvic floor muscles are good examples. These three muscles have the diverse effects of limb movement, facial expression and support of soft tissues respectively. The biceps (brachii) muscle of the upper arm is an example of a muscle that acts over a synovial joint (the elbow). The biceps has two tendon insertions on the scapula at its proximal end and a single distal insertion into the radius. The flat buccinator muscle of the cheek is an example of a muscle that inserts only into the connective tissue of skin to allow for the movements of the mouth. The muscles of the pelvic floor insert into bone (they are slung between the ischium of the pelvis and the sacrum and coccyx), but do not cause movement at a joint. Instead, by contracting they give support to the tissues of the pelvic floor and are important for maintaining continence of faeces and urine.



image Information Box 4.2a-III The muscles: comments from a Chinese medicine perspective


The muscles are made up of flesh, tendons and sinews. Their health is dependent on healthy Spleen, Liver and Gallbladder Qi.


Spleen Qi is more responsible for the springy fleshy quality resulting from healthy muscle tone, whereas Liver and Gallbladder Qi are responsible for the power of contraction and the movement that results.


The knots and excessive tone often felt in overtense muscles are usually a reflection of Liver Qi (and Blood) Stagnation. This, in turn, is more likely to occur in muscles that are weak as a result of Spleen Qi Deficiency.



image Information Box 4.2a-IV The musculoskeletal system: comments from a Chinese medicine perspective


In summary, a healthy musculoskeletal system is dependent on the health of the Kidney, Liver, Gallbladder and Spleen Organs. Kidney Essence is of particular importance to the bones. Healthy Blood and Yin are important for lubricating and nourishing the muscles and joints, as well as for preventing Stagnation of Qi. Hence, muscle and joint pains, stiffness or inflamed tendons can result if Blood and Yin, in particular of the Liver, are deficient.



image Self-test 4.2a The physiology of the musculoskeletal system




1. Why do you think it is that long bones are mostly made of compact bone, whereas the other types of bone are mostly composed of cancellous bone?


2. How is synovial fluid made? What is its purpose?


3. Why is it that our muscles can never be fully relaxed?



Answers




1. The long bones need to be strong because they have to withstand recurrent stress from lifting and weight bearing. Compact bone is a tissue that provides strength in the direction required. Strength is less important in the other bones. In the other bones (irregular, flat and sesamoid), cancellous bone minimises the weight of the bone and provides a site for the manufacture of the blood cells.


2. Synovial fluid is made by the cells of the synovial lining that covers the ends of the bones and the lining of the capsular ligament on the inside of the joint space. The fluid provides lubrication for the joint, contains immune cells, and also allows the passage of nutrients to the cartilage that covers the bony ends within the joint.


3. The muscles of the body are never in a state of full relaxation, even in sleep, because there is always a ‘background’ level of nervous stimulation of the muscles, which gives each muscle its tone. Without tone the muscles would become flaccid.



Chapter 4.2b The investigation of the musculoskeletal system



Learning points



At the end of this chapter you will:


• be able to recognise the main investigations used for diseases of the musculoskeletal system

• understand what a patient might experience when undergoing these investigations.

Estimated time for chapter: 30 minutes.



Introduction


Diseases of the bones, joints and muscles are investigated within two distinct conventional specialities. Diseases that are likely to require medical treatment with drugs are referred to a physician known as a rheumatologist, while those conditions that are likely to require surgery are referred to an orthopaedic surgeon.


An investigation of the musculoskeletal system might involve:



• a thorough physical examination


• investigations to examine the structure of the bones, muscles and joints (X-ray imaging, ultrasound imaging, magnetic resonance imaging (MRI) and bone scans)


• examination of the blood to look for disturbances in the hormones and chemicals that reflect bone disorders and autoimmune diseases


• examination of the synovial fluid of a joint


• arthroscopy, the endoscopic examination of the interior of a joint.


These investigations are considered briefly in turn below.



Physical examination


The physical examination is a very important aspect of the examination of the musculoskeletal system. A skilled examiner can identify the site and nature of a wide range of musculoskeletal problems without the need for further investigations. For each joint and muscle group there is a range of specific physical tests that can be performed to examine for particular disorders. For example, the FABER (flexion, abduction and external rotation) test is used to examine for a painful disorder of the hip joint.


The physical examination of the musculoskeletal system involves the stages listed in Table 4.2b-I.


Table 4.2b-I The stages in the physical examination of the musculoskeletal system







• Examination of the gait, posture and general appearance: this can reveal the characteristic features of musculoskeletal disease, such as a characteristic limp, areas of one-sided muscle wasting or postural deformity due to arthritis


• Examination of the muscle groups: looking specifically for areas of wasting or fine twitching, feeling for knots or swellings, and assessing the strength of the muscle groups


• Examination of the bones: looking specifically for areas of deformity or shortening, feeling for deformity, swellings or areas of tenderness, and percussion of the bones to examine for deep tenderness


• Examination of the joints: looking specifically for redness, swelling and deformity, feeling for heat and tenderness, and passively moving a joint to assess range of movement and the strength of the muscles that cause movement of the joint (active movement). In the case of a localised joint problem, the joint is examined using a range of specific tests



X-ray imaging


X-ray imaging is the most common investigation performed for musculoskeletal disease. This is because it is relatively cheap, quick to perform, and often produces an excellent picture of the bony structure of the body. The disadvantage of X-ray imaging is that it exposes the patient to radiation, although this is considered to be of minimal risk if X-ray imaging is only required on rare occasions during the lifetime of a patient.


However, X-ray images cannot reveal much information about muscle problems, and will only reveal changes of arthritis at a late stage in the condition, when the bony surfaces of the joint have become eroded. For this reason, the general medical view is that X-ray images are not helpful in the diagnosis of most cases of low back pain, which are usually the result of muscle strain, prolapsed disc or early arthritis, none of which are revealed on an X-ray image.



Ultrasound scan


This can be a useful and non-invasive test for the examination of a joint and the soft tissues that surround it. It is of particular value in the examination of the shoulder.



Magnetic resonance imaging (MRI)


MRI provides very high-quality information about joints and muscles, and reveals the structure of the low back in detail. However, it is expensive and can be uncomfortable for the patient to experience.



Bone scans


Bone scans involve the injection of a radioactive substance into the bloodstream. This substance is concentrated in areas of bone in which there is active growth, which are then revealed by scanning the body for radioactivity. This is useful for revealing areas where there may be a fracture or the site of bone cancer.


A DXA scan is a specialised form of X-ray imaging used to investigate the condition of osteoporosis. This form of bone scan does not necessitate injection of a radioactive substance. Instead, it uses a low-dose of X-rays to assess the degree of osteoporosis. The DXA scan is most usually performed in menopausal women and other people at risk of osteoporosis to assess need for medical treatment for this condition.



Blood tests


There are numerous blood tests that can give some information about certain diseases of the musculoskeletal system. A serum sample can give information about the levels of the mineral salts of calcium and phosphorus in the blood, as well as whether or not levels of hormones such as parathyroid hormone and calcitonin are within the normal range.


The erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) tests can indicate whether an inflammatory process is going on. There is a range of autoantibodies that can be assayed from a serum sample if an autoimmune disease is suspected. In the case of a chronic autoimmune disease, such as rheumatoid arthritis, a full blood count (FBC) may reveal anaemia of chronic disease.



Examination of the synovial fluid of a joint


Synovial fluid may be withdrawn from a joint by means of a needle and syringe for examination in the case of arthritis. If the joint is very swollen with fluid, this simple procedure may also give the patient relief from discomfort. In some cases, after withdrawal of the fluid, a corticosteroid drug may be injected directly into the joint through the same needle.


The fluid may reveal the microorganisms and pus characteristic of infection, and so can be a guide for appropriate antibiotic treatment. In the case of arthritis due to simple inflammation (e.g. autoimmune disease or osteoarthritis) the fluid will be clear. In gout the fluid will contain the microscopic crystals that are the cause of the pain.


There is a small risk of introducing infection into the joint with this procedure.



Arthroscopy


Arthroscopy is a procedure that enables the examination of the interior of a joint, usually the knee. It involves the insertion of a fine endoscope into the joint space via a small incision in the skin overlying the joint. A general anaesthetic is usually given. In this way, the integrity of the joint cartilage and any other structures, such as ligaments within the joint, can be examined. In some cases, surgery to the damaged structures within the joint (e.g. a tear in the cartilage within the knee) may be carried out at the same time.


Even if no surgery is carried out, many people report that chronic knee pain is relieved (usually temporarily) following arthroscopy.



image Self-test 4.2b The investigation of the musculoskeletal system




1. A 35-year-old female patient is referred to a rheumatologist because she has developed a painful condition of the joints in which a number of the joints (wrists, elbows, hips and knees) are swollen and warm. One knee in particular is very swollen with fluid. The patient is unwell and slightly feverish, and the joints feel very stiff in the mornings. The GP suspects rheumatoid arthritis. What investigations do you think this patient might have to undergo?


2. Faith is 55 years old. She has pain in the centre of her back. The GP suspects osteoporosis and is considering prescribing treatment to help prevent fractures. What investigations do you think the GP might perform?



Answers




1. The patient will be given a thorough physical examination in which the swollen joints are assessed and any joint deformities noted.


Blood tests will be ordered to examine for autoantibodies and anaemia in particular. A serum sample may also reveal some features suggestive of gout, which can also rarely give rise to a painful arthritis such as in this case.


X-ray images of the joints will be requested, although these may be normal at an early stage of an inflammatory arthritis. Nevertheless, they will be useful as a baseline against which to compare any future X-ray images should the condition progress. Other imaging tests are not likely to be helpful in this case.


Fluid may be withdrawn from the swollen knee joint to exclude the presence of infection or crystals, and to provide the patient with some relief from discomfort.


An arthroscopy would be unnecessary in this case.


2. Faith may undergo X-ray imaging of the painful part of her back. This might reveal the ‘thinning’ of the bones, which is characteristic of osteoporosis, and might also show if any of the vertebrae have become compressed as a result of the condition.


Blood tests might be performed to check that the mineral salts and hormones are within the normal range, which they should be in simple osteoporosis.


The other imaging test that can be useful is the DXA scan, which uses low-dose X-rays to assess the degree of osteoporosis in different parts of the body. This too can be used as a baseline against which progression of the condition and response to treatment can be assessed.


Examination of joint fluid and arthroscopy are not relevant to this case.



Chapter 4.2c The treatment of musculoskeletal pain



Learning points



At the end of this chapter you will:


• be able to describe the mode of action of the simple analgesics, the non-steroidal anti-inflammatory drugs and the opioid analgesics

• understand the principles of treatment with analgesics

• be able to describe how muscle relaxants and corticosteroid preparations may be used to relieve musculoskeletal pain

• be able to describe the use of non-drug methods of pain relief in conventional medicine.

Estimated time for chapter: 60 minutes.



Introduction


This chapter explores the way in which conventional medicine manages the problem of pain due to musculoskeletal disease. The approach to musculoskeletal pain can be broadly categorised into disease modification and symptom relief.


Disease modification involves the use of medication which actually alters the progression of the underlying disease. Because the disease has been slowed or halted, symptoms abate. The disease-modifying treatments are described in the next three chapters on diseases of the musculoskeletal system because they vary according to the disease being treated.


Symptom relief involves the use of medication or other therapies to block the sensation of pain. It does not attempt to alter the underlying disease process. Almost by definition, symptom relief is suppressive in nature. The most common form of symptom relief in musculoskeletal pain is the use of painkillers. The medical term for a painkiller medication is an ‘analgesic’.



Analgesics in musculoskeletal disease


Musculoskeletal disease is the most common reason for the prescription of analgesics. Analgesics are also used for a wide range of other conditions, including headache, menstrual pain and the pain of cancer. The analgesics used can be broadly categorised into simple analgesics, non-steroidal anti-inflammatory drugs (NSAIDs) and opioid (morphine-like) analgesics. These might be prescribed on their own or in combination with each other. There are, in fact, many analgesic preparations that contain a combination of two drugs that are believed to complement each other in their mode of action (e.g. co-codamol and co-dydramol, which combine paracetamol with codeine and dihydrocodeine, respectively). Other compound analgesics incorporate non-analgesic drugs such as caffeine or decongestant medication.


A vast range of analgesics is available for direct sale to the public. Many of these are compound preparations. These are listed at the end of Section 4.71 of the British National Formulary.



Simple analgesics


The simple analgesics are aspirin and paracetamol. Aspirin is anti-inflammatory in action, which means that it inhibits the chemical communication between the leukocytes that maintain the process of inflammation. Therefore, aspirin acts to reduce the heat (fever), redness, pain and swelling that are characteristic of inflammation. Paracetamol has a poorly understood mechanism of action. It is believed not to be anti-inflammatory. However, its effect is similar to that of aspirin in that it can reduce pain and fever.


Aspirin also reduces the tendency of platelets to stick together. This is why it is of value in the prevention of thrombosis and embolism. For this effect, a very low dose (75 mg) is required daily. The analgesic dose is much higher (up to 600 mg four times a day).


Aspirin tends to irritate the lining of the digestive tract, although in most cases this effect is mild and painless. However, in some people this can result in severe inflammation, with bleeding into the stomach (gastritis). Other side-effects include asthma and rashes. In children under the age of 12 years there is a very small risk of a severe form of inflammation of the liver called Reye’s syndrome.


Paracetamol has few side-effects in low doses, but in overdose it is highly toxic to the liver.


Simple analgesics are recommended for mild pain. Aspirin should not be given to children, and ideally should not be taken at analgesic doses for a long-standing (chronic) condition because of the risk of stomach irritation.



image Information Box 4.2c-I Simple analgesics: comments from a Chinese medicine perspective


In Chinese medicine, the reduction in pain from the simple analgesics corresponds to Movement of Stagnation and Clearance of Heat. In pain relief the action is suppressive in nature, as it clears the symptom locally without necessarily addressing the underlying cause.


Aspirin is believed to be generally Warming and Dispersing in nature. In some cases it may enable the clearing of Wind Cold by causing sweating and the Release of the Exterior. The Warm nature is evidenced by the side-effect of Heat in the Stomach. Asthma and rashes suggest that, in some people, aspirin may also depress Lung Qi and permit Wind Heat Invasion.


In high doses, the liver toxicity described in conventional medicine strongly suggests that paracetamol stagnates and damages the Liver Qi from a Chinese medicine viewpoint.



Non-steroidal anti-inflammatory drugs (NSAIDs)


The NSAIDs are a family of drugs that have an anti-inflammatory effect similar to that of aspirin. Like aspirin they can reduce pain, fever, redness and swelling, and they also have side-effects which include gastric irritation, asthma and rashes.


Commonly prescribed NSAIDs include ibuprofen and diclofenac.


NSAIDs generally have a more powerful effect than aspirin, and are particularly useful in any pain that has inflammation as its root cause. Therefore they are useful in the inflammatory conditions of the musculoskeletal system such as arthritis, tendon and ligament injuries, and most bony pain, including fractures. NSAIDs at maximum dose can be safely used in combination with paracetamol or with opioid analgesics to increase the effect of pain relief.


The side-effect of gastric irritation is less marked than for aspirin. Nevertheless, it is recommended that NSAIDs are taken with food. However, NSAIDs can also be toxic to the kidneys in susceptible people, particularly if taken at a high dose for a prolonged period. For this reason they should be used with caution in the elderly or in combination with other medication that may affect the kidney function.


The cyclo-oxygenase-2 NSAIDs (etoricoxib and celecoxib), which are selective inhibitors, were developed to minimise the risk of upper gastrointestinal bleeding, and short-term data suggest that they do indeed carry a low risk of bleeding events in clinical practice. However, there does seem to be an association between these cox-2 inhibitors and adverse thrombotic cardiac events, and so their use is reserved only for those situations when older generation NSAIDs cannot be used and risk of cardiovascular disease is low.


For reasons that are unclear, the response in terms of pain relief of an individual to different NSAIDs is unpredictable. For this reason a number of these drugs may be tried in succession before the best effect is found.



image Information Box 4.2c-II Non-steroidal anti-inflammatory drugs: comments from a Chinese medicine perspective


In Chinese medicine, the energetic action of NSAIDs is similar to that of aspirin. In the long term, the warming nature of these drugs may deplete Blood and Yin, primarily of the Liver and Kidney.



Opioid analgesics


This range of painkillers is so called because their action is similar to that of the naturally occurring drug opium. They all appear to mimic the effect of the body’s natural painkillers, the endorphins, and act within the spinal cord and the brain to reduce the sensation of pain.


The opioid analgesics provide strong pain relief, although they do not reduce inflammation directly. They are generally only used in musculoskeletal conditions when pain is very severe (e.g. after acute trauma such as a fracture). They may safely be used in combination with aspirin, paracetamol or the NSAIDs. The opioid analgesics include codeine, morphine, buprenorphine, diamorphine (heroin), dihydrocodeine, pethidine and tramadol.


The opioids are highly addictive, and also induce bodily tolerance to the effects of the drug. This means that, with recurrent use, increasing doses may be required to maintain a steady level of pain relief. They may induce a sense of euphoria or well-being.


The most common adverse side-effect is nausea and vomiting. This means that an anti-sickness medication may have to be prescribed at the same time. Constipation is also a common side-effect. With very high doses the depth of breathing may be inhibited, and the patient may fall into a stupor. In overdose, death may result from respiratory failure.



image Information Box 4.2c-III The opioids: comments from a Chinese medicine perspective


In Chinese medicine, the pain-relieving effect of the opioids seems to correspond to the Movement of Stagnation. This effect is suppressive in nature. The side-effects of euphoria and stupor may reflect the effect of Heat (at the Blood Level) on the Heart Organ. Constipation is also a result of Heat, in this case in the Small and Large Intestine. Suppression of respiration may reflect a depression of Lung and Kidney Qi. Nausea and vomiting might be seen as a manifestation of rebellion of Stomach Qi.



Other drugs used for symptom relief in musculoskeletal disease


The two other classes of drugs that are used for symptom relief in musculoskeletal disease are the muscle relaxants and the corticosteroids.



Muscle relaxants


An important drug used to relax tense muscles in musculoskeletal conditions is diazepam. This drug is most commonly prescribed for its effect in calming anxiety in minor mental illness (see Section 6.2).


In certain painful conditions of the joints and muscles, in particular low back pain, reflex muscle spasm can worsen the underlying pain and may slow healing by making the whole area surrounding the injury rigid. In cases such as these, diazepam may be prescribed for a short period (ideally a few days at the most) to relieve the pain and tension caused by the muscle spasm.


The side-effects of diazepam include drowsiness and unsteadiness of gait, but these are not usually problematic in short-term use for an acute musculoskeletal problem. Diazepam is also highly addictive, but again this should not be a problem when used in the short term.



image Information Box 4.2c-IV Diazepam: comments from a Chinese medicine perspective


From a Chinese medicine perspective, the calming and slowing effect of diazepam could correlate with a Cooling effect, and thus a depression of Yang, in particular of the Heart. Side-effects of drowsiness and unsteadiness indicate that in excess it might be seen as Phlegm Forming.



Corticosteroids


Corticosteroids may be used for their disease-modifying properties in the forms of arthritis that result from autoimmune disease (e.g. rheumatoid arthritis). In this case they are given regularly by mouth to calm the underlying inflammatory process.


Corticosteroids may also be administered by injection to reduce local inflammation in a wide range of musculoskeletal conditions. The injection can be directed into a joint in cases of arthritis, or around a tendon in cases of tendonitis (e.g. tennis elbow). The injection may bring about a rapid relief in the symptoms of inflammation, and can be relatively long acting (days to weeks).


The side-effects are mostly a consequence of the locally high concentration of steroid in the tissues. They include wasting of the tissues below the skin (fat atrophy) and, in rare cases, weakening of the connective tissue of the tendons themselves. Occasionally, tendons may rupture as a result. The anti-inflammatory properties of steroids may promote the development of infection (unchecked by the immune system), which can have disastrous effects within a joint.



image Information Box 4.2c-V Corticosteroid injections: comments from a Chinese medicine perspective


The effects of corticosteroid injections might be interpreted as Clearing of Heat by Moving of Stagnation. These effects are suppressive. Other side-effects (e.g. irritation of the stomach lining) suggest that corticosteroids are actually Heating in nature. Fat atrophy and wasting of tendons could be a manifestation of depletion of Yin and Qi of the tissues.



Non-drug methods of pain relief in musculoskeletal disease


Many patients with chronic musculoskeletal disease are referred to an orthopaedic physiotherapist who may use one or more of the following approaches to relieve pain. Unfortunately, because of the time-consuming nature of many of these therapies, they are not always available free of charge within the UK National Health Service (NHS).



Advice and training on posture and physical exercises


This is very commonly offered, as it is considered a therapy that can help patients to help themselves. Usually, a few appointments are offered to teach the patient some basic exercises to help strengthen muscles or stretch out tense areas. It is probably true that if all patients could stick to an allotted exercise regimen much discomfort from muscular and arthritic problems would be relieved. Unfortunately, many people are not able to generate the commitment required for a regular exercise and posture routine, particularly if little long-term follow-up of their progress is arranged.



Manipulation and massage


Some physiotherapists are skilled in the manipulation of joints and massage of tense muscles. These therapies can relieve muscle spasm, but may need to be repeated to be of long-term benefit. Heat and ice packs may also be used to relieve pain and swelling.



image Information Box 4.2c-VI Exercises, massage and manipulation: comments from a Chinese medicine perspective


The Chinese medicine interpretation of attention to appropriate exercise and correction of posture is that it helps to move Stagnant Qi and benefits the Kidneys. This is an energetically appropriate treatment, as long as it is not too strenuous.


Massage and manipulation would be seen as moving Stagnant Qi and Blood. If an underlying imbalance is not attended to, this form of therapy can be suppressive in nature, dissipating a symptom without addressing the underlying cause.



Ultrasound, TENS and local acupuncture


These three approaches are used by physiotherapists to relieve the pain in localised musculoskeletal problems. Ultrasound therapy involves focusing ultrasound waves so that they are concentrated at the site of the injury. TENS (transcutaneous electrical nerve stimulation) involves the passage of a low-voltage electrical current across the affected area of the body via electrode pads fixed to the skin. The acupuncture offered in the NHS often involves the use of local and tender (Ah-shi) points.


The mechanism of all three approaches is not clearly understood in conventional terms, although there is a belief that all have a similar action in stimulating suppressive neurotransmitters (including endorphins) within the spinal cord and the brain.



image Information Box 4.2c-IX Ultrasound, TENS and local acupuncture: comments from a Chinese medicine perspective


In Chinese medicine, all three of these treatments will move Blood and Qi Stagnation and may enable the Clearance of Pathogenic Factors. However, if the underlying imbalance is not attended to, all three may be suppressive in action.



Anaesthetic and surgical approaches to pain relief


In some cases of severe intractable pain, specialised procedures can be performed to reduce the sensation of pain. These involve the deadening or destroying of nerves or nerves roots within the peripheral nervous system. These procedures are carried out by anaesthetists or surgeons. It is extremely rare for these procedures to be necessary in musculoskeletal pain, although they may be used in cases of severe chronic low back pain.



image Self-test 4.2c The treatment of musculoskeletal pain




1. A 60-year-old patient is taking three 200 mg tablets of ibuprofen a day for a constant pain in both hips. This pain has been diagnosed as early osteoarthritis. Because she gets slight indigestion if she takes any more tablets than this, her GP recommends that she also takes up to 4000 mg/day of paracetamol to relieve her pain. She finds she often needs to take all these tablets. Do you think that this approach to symptom relief is a reasonable one in conventional terms?


2. A 27-year-old gardener has suffered a sudden onset of back pain while digging. He is in so much pain that he is unable to drive himself home, and finds that his only relief is to lie flat on the floor. The GP examines him on a home visit and finds excessive muscle spasm in the lumbar area. Flexion of the hip joint induces pain on the left-hand side which radiates into the buttock and down the back of the leg (sciatica).


(i) What medication do you think the GP might prescribe?

(ii) Assuming that the condition is much better 5 days later, but is still very tense and painful, what other additional treatment approaches might the GP consider?


Answers




1. The GP has prescribed reasonably in conventional medicine terms. Ibuprofen is the best choice for arthritis, as long as the patient can tolerate its side-effects. In the short term, maximum-dose paracetamol is considered relatively safe, and may complement the action of the ibuprofen.


Nevertheless, both these treatments are suppressive, and in the long term may be causing increasing energetic imbalance. This issue is not really accepted in conventional medicine, although serious adverse effects such as gastritis and kidney damage are, of course, recognised as rare complications of this treatment.


2.


(i) If the pain is very severe the GP might consider giving a single dose of an opiate mediation by injection, but this would be unusual. The most usual approach would be to offer a regular dose of a NSAID, with the option of a combined paracetamol and opiate preparation (e.g. co-codamol). In addition, diazepam might be prescribed for a few days to relax the muscle spasm. Current advice is for the patient to continue to move the back gently as soon as possible (mobilisation rather than bed rest; see Chapter 4.2f).

(ii) If the patient is improving but pain and spasm are persisting, the GP might consider referral to a physiotherapist so that the patient can be taught some back and postural exercises. The physiotherapist might also choose to offer additional therapies such as massage, TENS and acupuncture, according to his or her interest, training and the time available. If the problem persists the GP might decide to refer the patient to an orthopaedic surgeon for further investigation of the back pain (see Chapter 4.2e).


Chapter 4.2d The diseases of the bones



Learning points



At the end of this chapter you will:


• be able to name the main features of the most important diseases of the bones

• understand the principles of treatment of a few of the most common diseases

• be able to recognise the red flags of the diseases of the bones.

Estimated time for chapter: 120 minutes.



Introduction


This chapter is concerned with the important diseases that affect the bones. The diseases of the bone marrow have already been summarised in Chapter 3.4e. The conditions studied in this chapter are:



• Generalised disorders of the formation of bone (see Q4.2d-1)image:


– osteoporosis

– Paget’s disease.

• Rickets and osteomalacia (vitamin D deficiency).


• Inherited or childhood bone disorders:


– achondroplasia

– brittle bone disease.

• Infection of the bones:


– osteomyelitis.

• Tumours of the bone:


– benign tumours

– malignant osteosarcoma.

• Metastatic disease of the bone:


– myeloma.


Generalised disorders of the formation of bone



Osteoporosis


‘Osteoporosis’ is a term used to describe a condition in which the actual amount of bony material within the bones is decreased, meaning that there are more spaces within the bone tissue. This has the effect of weakening the bones, and the bones look pale on an X-ray image. In laymen’s terms, the bones in osteoporosis are ‘thin’. In conventional medical terminology the term ‘low bone density’ means the same thing.


The solidity or density of bone normally rapidly increases as a response to the hormone surge of puberty. At this time the bones in a healthy adolescent become more heavy and resistant to fracture. From the age of about 40 years onwards there is a progressive natural decline in this density of bone. This decline is called ‘bone loss’. In men the bone loss continues gradually into old age. In some women the rate of bone loss increases very rapidly at the menopause, when the natural levels of oestrogen suddenly drop, and bone density can suddenly become significantly reduced over a relatively short period of a few years.


Certain factors reduce the rate of bone loss. These include a healthy vitamin- and calcium-rich diet and a moderate level of physical activity from childhood. Weight-bearing physical activity (e.g. walking and running rather than swimming) is known to be particularly important in the maintenance of good bone density.


Factors that increase the rate of bone loss include a poor diet, physical inactivity, reduced levels of oestrogen in women (including early menopause), smoking and chronic diseases. The amenorrhoea that affects some women athletes and women with anorexia will lead to thinned bones if prolonged. It follows that excessive physical activity may not necessarily be so beneficial to the bones in women. Numerous pregnancies and prolonged periods of breastfeeding will also deplete calcium reserves in the bone. It is now known that it is very significant if any of these factors are present in adolescence, as the bones will then never achieve the optimum starting point of bone density after the growth spurt. This is of concern in westernised countries today in which adolescents tend to live an increasingly sedentary existence and eat a highly processed diet. In addition, particularly in girls, eating disorders are increasingly prevalent in younger age groups.


Osteoporosis is of enormous health concern in developed countries, in which there is an increasing proportion of the population who are elderly. Osteoporotic hip fractures will affect 15% of all women and 5% of men from the age of 60 years. A hip fracture can have disastrous consequences in an elderly person. A high percentage of people who suffer from these fractures either die as a direct result of the injury or complications of the fracture, or suffer from long-term disability.


The symptoms of osteoporosis can be broadly categorised according to the age and sex of the patient, although there is much overlap between the categories.


In some postmenopausal women a very rapid decline in cancellous bone mass causes the vertebrae in the cervical and thoracic spine to thin very quickly. These spongy bones are then at risk of collapsing under the weight of the head and upper body. This form of ‘crush fracture’ can be very painful and will lead to progressive bowing forward of the upper back. In extreme cases, a so-called ‘dowager’s hump’ results. In addition, there is particular thinning of the distal end of the radius, which means that a fall onto the outstretched hand may lead to a fracture of the wrist (Colles’ fracture).


In more elderly people (over the age of 70 years) the strength of the compact bone of the long bones is more gradually reduced, and it is at this stage that hip fracture becomes more common. The vertebrae of the spine also soften and compress down, but because the bone loss is less abrupt, sudden painful crush fractures are less common.


The ideal approach to the management of osteoporosis is prevention. Ideally, this begins in adolescence with a calcium-rich diet and regular moderate weight-bearing exercise. Women, in particular, should also be encouraged to keep up a calcium-rich diet, particularly when breastfeeding. All people should keep up a steady level of activity throughout adult life in order to minimise the rate of bone loss.


Osteoporosis can be graded in severity by means of a DXA scan, in which bone density of the lumbar spine and hip are assessed. The results are expressed in the form of a ‘T score’, in which a negative value suggests lower than predicted bone density for a young healthy adult. A T score below –1 would lead a doctor to consider preventive medical treatment.


Hormone replacement therapy (HRT) used to be a widely prescribed preventive treatment for osteoporosis in perimenopausal and postmenopausal women. However, recent clinical research following large groups of women on HRT has prompted the UK Committee on the Safety of Medicines (CSM) to advise that HRT is no longer recommended as a principal (“first-line) treatment. This guidance has come in the light of an established link between HRT and an increased risk of breast cancer, ovarian cancer and endometrial cancer. The clinical studies also demonstrated that HRT has a less protective effect against the development of coronary heart disease than was previously believed.


The bisphosphonates form a class of drugs that is increasingly used in established early osteoporosis. These drugs prevent the action of the osteoclasts in breaking down bone, and do seem to slow bone loss, and reduce the fracture rate. Alendronate and clodronate are two types of bisphosphonate in common use. Nausea and oesophagitis are unwelcome common side-effects. These drugs may be prescribed together with calcium and vitamin D.


Calcium and vitamin D in a low-dose preparation may be prescribed together as a preventive treatment in elderly people. This treatment, which is less well supported by evidence of benefit than the biphosphonates, should be unnecessary if dietary intake is adequate, but a poor diet and poor absorption may work together in old age to reduce intake of calcium.


A late preventive measure is to prevent the occurrence of falls in the elderly. Exercise programmes can improve muscle strength and improve balance, and therefore may prevent falls. Regular Tai Chi classes are one of the active measures that have been shown in experimental studies to reduce the incidence of falls in elderly people.



image Information Box 4.2d-I Osteoporosis: comments from a Chinese medicine perspective


In Chinese medicine, the thinning of bones in osteoporosis corresponds to deficiency of Kidney Jing. The gradual decline in bone density corresponds to the idea in Chinese medicine that Essence gradually declines from its maximum flourishing state in early adulthood. Attention to a healthy diet and moderate exercise will allow for a measured and natural decline of Kidney Yin and Jing, whereas under- or overexercising and undereating will deplete Kidney Yin and Jing. Pregnancy and breastfeeding are draining of Blood and Yin.


The hormone oestrogen is nourishing to the Spleen and to Yin, as evidenced by its beneficial effect on fleshiness and fertility. Hormone replacement therapy (HRT) likewise Boosts Yin, but this may be at the expense of drawing on reserves of Kidney Yin and Jing. The common side-effects of HRT include headaches, fluid retention and weight gain. There is also an increased risk of breast, ovarian and womb cancer. This suggests that there is additional Stagnation of Liver Qi and accumulation of Phlegm and Damp. These symptoms could be a form of drug-induced disease, as HRT is not identical to natural oestrogen. As HRT actually ‘suppresses’ the natural progression to the menopause, these symptoms may even be a form of expression of suppressed imbalance.


By slowing bone loss, bisphosphonates directly Boost the Kidneys and Jing, but are depleting to Spleen Qi and Stomach Yin, as evidenced by the very common side-effects of nausea and oesophageal ulceration. They are suppressive in nature. Vitamin D and calcium nourish the bones, and therefore are nourishing to the Kidneys and Jing. In normal dietary quantities this treatment is curative in nature.

Related posts:

Infectious disease Comparisons with alternative medical viewpoints Diseases of the endocrine system The urinary system Diseases of the nervous system Gastrointestinal disease

Stay updated, free articles. Join our Telegram channel
Tags:
Oct 3, 2016 | Posted by in MANUAL THERAPIST | Comments Off on The musculoskeletal system

Full access? Get Clinical Tree
Get Clinical Tree app for offline access