1
Chapter 12
Bone and joint diseases
Soft tissue tumours
Muscle diseases
Topics to be discussed in this chapter are
Fractures
Infection
Arthritis
Osteo arthritis
Rheumatoid arthritis
Gout
Paget’s disease
Metabolic bone disease
Tumours
benign
malignant
primary
secondary
Soft tissue tumours
Muscle diseases
Fractures
Perhaps the most frequent pathological
condition of bones is fracture.
Bones are broken by many different types of
physical trauma.
Most fractures are simple and can be ‘mended’
by keeping the two ends of the broken bone
together and keeping them still until the natural
healing process results in their repair.
This can be done by the application of a plaster
of Paris bandage.
1 This X-ray shows a fracture of the forearm,
one of the commonest fractures encountered.
The radius (yellow arrow) is broken. The ends
of the broken bone are jagged and the two
broken bones are not properly aligned.
To get a good healing result, the forearm is
‘manipulated’ to bring the fragments into
alignment before applying a plaster of Paris
bandage.
The red arrow indicates the unbroken ulna, and
the yellow arrow the bones of the wrist.
This type of fracture is called a ‘closed’ fracture
as distinct from a ‘compound’ one in which the
skin is broken and the bone ends protrude
through the skin.
The latter is a more serious fracture because it
is exposed to the environment and infection is a
likely complication.
Infection greatly slows the healing of the
fracture and may result in further
complications.
Fractures of some other bones do not heal
easily with simple plaster fixation. They require
‘internal fixation’ using nails, plates and
screws.
Orthopaedic surgeons use scrupulously aseptic
techniques in treating such fractures because
there is an ever present risk of infection.
Two fractures that need internal fixation for
treatment are illustrated
Ankle
2(a) and (b) This combined image shows
(a) an X-ray of a fractured right ankle and
(b) an X-ray of a similar fracture that has been
treated by internal fixation with a screw and a
plate.
Red arrow tibia
Green arrow fibula
Yellow arrow talus bone of the ankle
A fracture of the ankle usually results in
fracture of the lower end of the tibia and
fracture of fibula as shown.
The X-ray of the fixation shows the fracture of
the tibia fixed with a screw and that of the
fibula by a plate.
2
After surgery, the ankle is immobilized in a
plaster cast.
This resulted in death.
Infection
Hip
Fractures of the neck of the femur are common
in elderly people.
They result from a fall.
The patient is unable to walk unless the two
ends of the fractured bone become ‘impacted.’
If the patient is frail this is often the final
episode that results in death.
In the middle of the 20th century, treatment of
fractured neck of femur was revolutionized by
the introduction of a ‘nail’ that is inserted as
shown in the specimen. A number of different
designs of this nail are in use.
3 Fractured neck of femur with a surgical nail
that became infected.
Unfortunately the patient died of other causes
about two weeks after the operation.
Complications of fractures
Fractures may not unite properly and this
results in a number of different problems which
include
non union
malalignment and shortening of bone which is a
problem in healing of fractures of weight
bearing bones – vertebrae and leg bones.
Infection of compound fractures.
This leads to the complications listed under
the heading of osteomyelitis.
Fat embolus
4 This brain specimen came from an autopsy on
a young man who had a motor bike accident.
He suffered compound fractures of both femora
and soon after the accident he became
unconscious and died as a result of fat emboli.
In the slice of brain, the sites of the fat emboli
can be seen as multiple petechial haemorrhages
throughout the white matter.
As a result of the fracture, fat from the marrow
cavity entered the lacerated vessels and caused
fat emboli which blocked the small arteries to
his lungs and the white matter of his brain.
Infection of bone is called osteomyelitis.
A wide range of organisms may cause
osteomyelitis but the commonest one is
Staphylococcus aureus.
Any bone in the body may become infected.
Treatment of osteomyelitis has always been
difficult because of the relatively poor blood
circulation to the bone.
Before the mid 20th century when antibiotics
became readily available, chronic osteomyelitis
was a medical ‘headache.’
In osteomyelitis, pus is enclosed within the
bone marrow cavity by the thick cortical bone.
Over time, the pus breaks through this barrier
and sinuses develop on the skin surface. The
sinuses continue to discharge pus and fragments
of necrotic bone for months or years.
Infection may spread by the blood stream to
other organs resulting in metastatic abscesses.
Very rarely, squamous cell carcinoma
developed on the skin adjacent to the
discharging sinuses.
In the early part of the 21st century antibiotics
are becoming less effective and some of the
complications that used to be seen are being
seen again.
5(a) and (b)
(a) PA and (b) lateral X-ray views of the tibia in
a child.
They show the features of an acute
osteomyelitis.
Brown arrow elevation of the periosteum by
pus escaping from the medullary cavity.
Green arrow lytic destruction of a segment of
the cortical bone by pus extending from the
marrow cavity.
Clinically the patient will have a temperature
and there will be pain over the site of the
infection.
3
6(a) and (b) This image shows both front (a)
and back (b) sides of a specimen of sterno
clavicular joint that was affected by acute
osteomyelitis.
This is a very unusual site for osteomyelitis, but
it illustrates the features of this condition.
Green arrow sternoclavicular joint
Red arrow sternum.
The green arrow in (b) shows purulent exudate
within the joint.
The joint has been destroyed by fibrosis that
was part of the chronic inflammation that
resulted as the acute process did not heal
quickly.
7 This specimen of spine shows vertebral
collapse (red arrow) from the effects of chronic
osteomyelitis.
Figs. 6 and 7 show show old specimens from
the days before the introduction of antibiotics.
Tuberculosis
Tuberculosis is still a very common infection in
many countries in the world.
Bone tuberculosis tends to affect the big joints
and the spinal column.
When it involves the vertebral bodies, it
frequently destroys the vertebrae and produces
a paravertebral abscess.
8 X-ray of a patient from Papua New Guinea.
He has a tuberculous infection that is involving
his thoracic vertebrae 8 to 10. T 9 has collapsed
and pus has escaped and stripped along the
periosteum of the vertebrae causing a
paravertebral abscess.
The collapsed vertebra caused paraplegia as a
result of pressure on the spinal cord.
Arthritis
Osteoarthritis
This is a degenerative condition which affects
particularly the knees, hips and vertebral
column.
Fingers are frequently involved and other joints
are less frequently involved.
It is an ageing process and occurs in people past
middle age.
Excessive trauma and injury to the large joints
appear to predispose to an earlier onset of
osteoarthritis.
Pathologically the articular cartilage of the joint
particularly the hip and knee joints, becomes
damaged, fragmented and eroded.
Fibrosis of the joint capsule occurs and
overgrowths of bone (osteophytes) occur at the
edges of the bone.
This results in progressive stiffness in the joint
and pain which, at least in the earlier stages of
the disease, is intermittent.
9 This knee joint shows the features of
osteoarthritis. The condyles of the femur are
above and the left one is seen best.
The articular cartilage is greatly eroded and the
bare bone has been exposed.
The articular cartilage of both condyles of the
tibia are also severely eroded.
The cruciate ligament that holds the femur and
tibia together has been ruptured as well. (red
arrow)
Since the late 20th century, joints affected like
this one have been treated by knee replacement
with various types of prosthetic joints.
Replacement of hip joints has also been done.
The results are on the whole satisfactory, but
significant complications do occur.
Replacement of finger joints has not been as
successful as replacement of hips and knees.
Rheumatoid arthritis
This is an autoimmune disease.
It is much more common in females than in
males.
It usually occurs in middle age, but it can occur
at any age.
It affects the joints of the hands and feet at first,
but other joints become involved as the disease
progresses.
It runs a prolonged and intermittent course and
the arthritic pathology is accompanied by
systemic symptoms.
4
The joints are stiff, painful and become
deformed.
corresponding articular surfaces on the base of
the skull.
This allows the head to ‘nod’ up and down.
The early pathology is a chronic inflammatory
cell infiltration of the synovium and swelling of
the joint.
The inflammatory process grows over the
articular cartilage destroying it and causing
adhesion between the articular surfaces of the
joint with resultant stiffness, deformity and
finally fusion.
The odontoid process is really the missing body
of the atlas and it is fused to the upper surface
of the body of the axis.
This ingenious arrangement allows the head to
swivel around and to move forwards and
backwards.
10(a) and (b)
(a) a knee joint and
(b) a head of femur from the hip joint of a
patient who during life suffered from advanced
rheumatoid arthritis.
In a judicial hanging in which the prisoner is
suddenly ‘dropped’ through a trapdoor at his
feet, the sudden tightening of the hangman’s
noose breaks the upper cervical vertebrae and
the odontoid process presses on the midbrain as
shown in this specimen. This results in sudden
death.
(a) The knee joint had to be dissected so that it
could be opened and the pathology viewed.
Red arrow the articular surface of the patella in
the patella tendon.
Yellow arrow the articular surface of the patella
on the anterior surface of the femur.
Green arrow shows the adhesion between the
articular surfaces of the femur and tibia.
Purple arrow eroded articular surface of the left
tibial condyle.
(b) Articular surface of the head of the femur.
There is extensive destruction of the articular
surface (blue arrow).
11 This is an unusual complication of
rheumatoid arthritis.
The first and second cervical vertebrae become
fused together, and the odontoid process of the
second cervical vertebra protrudes through the
first cervical vertebra and impinges on the brain
stem. (red arrow).
Pressure at this point may cause sudden death.
Anecdote
The first cervical vertebra is called the atlas.
It has no body and is virtually a rim of bone
that swivels around the odontoid process of the
second cervical vertebra (the axis).
This allows the head to turn from side to side.
On its upper surface the atlas has two lateral
articular surfaces that engage the two
Arthritis due to gout
Gout is a metabolic disease in which there is an
impairment in the ability to metabolise uric
acid, and the patient has a high serum uric acid.
This results in high levels of uric acid being
passed in the urine, and resultant renal disease.
It is more common in men than in women.
It has a familial incidence.
Uric acid crystals are deposited in joints and in
subcutaneous tissues.
In the latter this results in the formation of
nodules called ‘tophi.’
In joints the uric acid crystals cause painful
arthritis that is intermittent and progressive.
The first joint to be affected is very frequently
the metatarsophalangeal joint of the big toe.
This presents as a very painful, red joint and is
usually associated with systemic malaise and
fever.
Other joints become progressively involved.
12 Knee joint, (red arrow)
MPJ of a big toe (purple arrow) and
patella (green arrow) from a patient who died
from the complications of gout.
These specimens demonstrate the deposition of
urate crystals in gout affected joints.
5
The toe and the patella are more affected than
the knee.
13 Specimen of an ankle joint with a gouty
tophus in the subcutaneous tissue adjacent to
the fibula. (red arrow)
Paget’s disease
Paget’s disease of bone is a moderately
common, non metabolic disease of bone whose
cause is not known.
It occurs in both males and females, usually
after middle age.
One or more bones may be affected and this is
not symmetrical.
The cortices of the bones become thickened and
they are soft and vascular.
When the tibia is involved it tends to bend with
an anterior bowing.
The skull enlarges and causes pressure on the
brain, and headache.
The vascularity of the bones may precipitate
heart failure.
A rare complication is an osteogenic sarcoma
arising in any of the diseased bones.
14(a) and (b) The skull (a) shows the gross
thickening characteristic of Paget’s disease.
Even though the bone was thick, it cut easily
with a scalpel blade.
(b) is a tibia which shows marked thickening of
the cortical bone (red arrow).
In this case, the whole length of the tibia shows
thickening of the cortical bone.
Quite often only portion of the bone is
thickened and the rest is of normal thickness.
Metabolic bone disease
Osteoporosis
This is defined as a loss of bone mass.
The bones become thin and fragile.
Fractures of long bones occur, crush fractures
of vertebrae occur with loss of height and
pressure on spinal nerves.
There are a number of different causes:
Idiopathic which occurs particularly in
postmenopausal women.
As a complication of long term steroid
therapy.
Disuse atrophy in patients confined to bed or
in limbs that are immobilized as a result of
treatment of fractures.
15 X-ray lateral view of the thoracic vertebrae
of a post menopausal woman.
It shows marked loss of bone density
(osteoporosis), and wedging of vertebrae from
collapse of vertebral bodies.
The red arrow indicates the most obvious one.
This deformity results in anterior bending of the
thorax (kyphosis) and loss of height.
It may also result in pressure on nerve roots as
they pass through vertebral foramena.
This causes local pain and sensory and motor
loss in the distribution of the nerve root
16 This specimen of thoracic vertebrae shows
collapse of osteoporotic vertebrae with
extrusion of the nucleus pulposis posteriorly
causing compression of the spinal cord. (red
arrows)
The patient had paraplegia as a result of the
compression.
17 X-ray showing osteoporosis of the lumbar
vertebrae.
Some of the vertebrae are crushed or wedged
anteriorly.
The red arrow indicates a point at which the
nucleus pulposis of the intervertebral disc has
herniated into the body of the vertebra below it.
Such herniations of the degenerate disc may
occur posteriorly or laterally in which case they
can compress either the spinal cord itself or the
nerve root at the site of herniation.
6
18 Specimen of lumbar spine showing
degeneration of a number of intervertebral
discs.
The green arrow indicates a herniation of disc
material into an adjacent vertebral body.
22 X-ray of left humerus which shows a pseudo
fracture of osteomalacia. (red arrow)
23 Xray of pelvis of a normal reproductive aged
woman. Note the normal symphysis pubis.
a x4
b x10
19(a) and (b) Normal cancellous bone.
The green arrow indicates the ostroblasts that
form the bone.
The blue arrow shows mature osteocytes.
(a) x4
(b) x10
20(a) and (b) Osteoporotic cancellous bone.
21 Normal cortical bone. Green arrow an
osteocyte. (x10)
Osteomalacia
This is a condition in which there is abnormal
formation of bone that results from abnormality
of calcium and phosphate metabolism. This in
turn is caused by deficiency of vitamin D.
Causes of vitamin D deficiency
Dietary deficiency of vitamin D – rickets.
Decreased absorption of vit D in malabsorption
syndrome.
Excessive amounts of circulating parathormone
in hyperparathyroidism.
Disordered metabolism of calcium and
phosphate occurs in chronic renal disease which
causes secondary hyperparathyroidism.
Renal osteodystrophy occurs in chronic renal
disease and this consists in a mixed pathology
of hyperparathyroid bone disease and
osteomalacia. (see Fig.)
X-ray features of osteomalacia
Pseudo fractures (cortical defects) are seen in a
number of different bones.
The symphysis pubis develops a ‘moth eaten’
appearance.
24 X-ray of pelvis of a patient with
osteomalacia. It shows a ‘moth eaten’
appearance of the symphysis pubis (red arrow).
(a) x10
(b) x10
25(a) and (b) Von Kossa stain showing the
bone trabeculae stained black and the osteoid
seams stained red.(green arrows)
In normal cancellous bone osteoid seams are
not prominent and when seen they are thin.
In osteomalacia, as shown here, the seams are
very obvious and very thick.
Bone biopsy to measure the thickness of
osteoid seams is one of the definitive tests for
the presence of osteomalacia.
Tumours
Benign
Malignant
Multiple myeloma (a tumour of
haematopoietic cells)
Jaw tmours
Metastatic
Benign tumours
Many varieties of benign bone tumours are
encountered, for example tumours of
Cartilage
Cancellous and cortical bone
Connective tissue, fibrous and vascular
Only a few will be demonstrated
Osteochondroma
These tumours appear as hard projections from
the surface of long bones near one end. (the
diaphysis.)
7
They are easily diagnosed by X-ray and they
are treated by being shaved off the surface of
the bone.
The thin walled vessels in the cystic lesion can
just be seen.
The cortical bone has been eroded.
They consist of a growth of cancellous bone
covered by a cap of cartilage.
(b) is an amputated forearm showing the
presence of an aneurysmal bone cyst (red
arrow) at the distal end of an ulna. (green
arrow)
Surgical treatment would now be aimed at
removing the tumour locally and replacing the
bone defect.
At the time that this patient was treated, the
entity had not been fully characterised and the
surgeon treated it as a malignant tumour.
(a) and (b)
(c) and (d)
26(a), (b), (c), (d)
(a) X-ray of an osteochondroma protruding
from the posterior aspect of the upper end of
the tibia. (red arrow)
(b) Osteochondroma (red arrow) gross
specimen of the upper end of a humerus
removed for other pathology.
(c) An osteochondroma that was shaved off the
surface of a long bone.
The thick cartilage cap shows the typical bluish
appearance.
(d) A microscopic section (x1 magnification) of
an osteochondroma with a light blue staining
cartilage cap and a base of cancellous bone.
Aneurysmal bone cyst
This is a benign tumour that consists of a
proliferation of thin walled blood vessels in the
bone.
It usually occurs in teenagers and involves
vertebrae and flat bones (e.g. ribs).
It also occurs in long bones.
X-ray shows a multicystic lesion that expands
beyond the cortex of the bone and causes
destruction of the cortical bone.
The cysts have thin walls which line vascular
spaces.
It is this expansion beyond the cortical bone
that has given it its name because it expands
like an aneurysm.
27(a) and (b)
(a) is an X-ray of the volar surface of the left
forearm.
It shows a typical appearance of an aneurysmal
bone cyst.
Malignant tumours
A variety of malignant tumours occur and they
have many subtypes which can be identified on
radiological and microscopic criteria.
As one would expect, the commonest tumours
arise from either bone or cartilage.
Imaging techniques now make it possible to
identify the exact extent of the tumours before
surgery is undertaken.
This allows surgeons to treat malignant bone
tumours by conservative limb sparing
operations rather than the radical amputations
that were done before the introduction of
sophisticated imaging techniques.
The specimens to be demonstrated in this
section were obtained some years ago from
radical amputations performed to treat the
tumours.
The two most common tumours will be
illustrated.
Osteosarcoma and chondrosarcoma.
Osteosarcoma
This is a tumour of bone forming tissue.
It occurs mainly in teenagers and young adults.
The commonest sites of origin of these tumours
are in the lower femur and in the upper tibia.
(That is around the knee joint.)
It presents with symptoms of a deforming
‘lump’ in the bone, pain or in advanced cases,
fracture.
8
Such fractures are called pathological fractures
to distinguish them from fractures due to
trauma.
There is a second small peak of osteogenic
sarcoma in older adults in association with
Paget’s disease of bone.
It is one of the tumours that can be caused by
excessive exposure to radiation either naturally
occurring, or following radiotherapy treatment
of other tumours.
28 (a) and (b) consist of front and back views of
the lower end of a femur.
The red arrows indicate the femoral condyles.
(a) An osteosarcoma is almost replacing the
whole lower third of the bone.
It has penetrated through the cortex and
periosteum into the adjacent muscle and
connective tissue (yellow arrow)
It has breached the articular cartilage and is just
entering the joint (white arrow).
29 This is an osteosarcoma which has arisen in
the upper part of the tibia.
It has extended along the shaft of the bone and
penetrated through the cortex and periosteum
(red arrow).
The green arrow indicates the intact cortex at
the distal end of the specimen.
Some of the haemorrhage is spontaneous, but
that near the red arrow resulted from the bone
biopsy that was done before the lower leg was
amputated.
Chondrosarcoma
This is predominantly a malignant tumour of
cartilage.
It occurs almost exclusively in adults.
It occurs in long bones and also in bones such
as pelvis and scapula.
Comment
Microscopically many osteosarcomas and
chondrosarcomas show mixed features of
osteoid and cartilaginous tissue and it requires
an experienced pathologist to categorise them
accurately.
30(a) and (b) This X-ray of the upper femur
shows the characteristic features of a
chondrosarcoma.
There is an osteolytic lesion through which
there are focal spotty areas of calcification.
31(a) and (b) This is the surgical specimen that
corresponds with the X-ray.
The tumour has replaced the head and neck of
the femur and is extending down the shaft of
the bone.
The haemorrhage is the result of the bone
biopsy performed before operation.
32 This is a chondrosarcoma that arose from the
ischium of the pelvis.
Its cut surface shows the bluish colour often
seen in cartilage tumours whether they are
benign or malignant.
Chondrosarcomas are not sensitive to
radiotherapy and the operation of
hemipelvectomy is rather horrendous.
Metatastatic potential of bone tumours
Bone tumours metastasise particularly to lung
and to brain.
33(a) and (b) Female 39 who died with
metastatic chondrosarcoma in lung (a) and
brain (b)
Multiple myeloma
A tumour of haematopoietic tissue in the bone
marrow.
Multiple myeloma is a malignant proliferation
of plasma cells.
These cells accumulate in the bone marrow as
localised deposits.
This may cause bone pain particularly when the
vertebrae are extensively infiltrated and they
collapse causing pressure on spinal cord and
nerve roots.
9
Multiple myeloma usually occurs in late middle
age and is slightly more common in males than
in females.
The haematopoetic aspects of this disease are
discussed in Chapter
Microscopic examination is needed to
determine the site of the primary tumour in
secondary tumours in bone.
34 Lumbar spine showing multiple
haemorrhagic deposits of multiple myeloma in
the vertebral bodies and vertebral spinous
processes (red arrows).
Many of the tumours that affect other bones
also occur in the jaws.
However there are a few tumours that
specifically arise in the jaws.
One of these, and perhaps the most common
one is the ameloblastoma which arises from the
tooth forming epithelium.
In passing note the filum terminale (green
arrow) and cauda equine (blue arrow) of the
spinal cord.
35 Skull from a patient who died from multiple
myeloma.
Multiple rounded haemorrhagic deposits of
myeloma cells can be seen throughout the skull.
This gross appearance is seen on plain X-ray of
the skull as multiple ‘punched out’ areas.
Metastatic tumours
Many tumours metastasise to the vertebrae.
They are usually osteolytic and result in
collapse of the vertebrae causing pressure
effects on spinal cord and spinal nerve roots.
Tumours that particularly metastasise to bone
are breast, lung, kidney, thyroid and prostate.
Prostate secondaries often produce
osteosclerotic deposits.
36 Spine from a male 63 showing the thoracic
vertebrae.
All the vertebrae except the one marked with
the red arrow contain secondary deposits of
tumour which were identified as being from a
lung cancer on microscopic examination.
37(a) and (b)
(a) vertebrae almost completely replaced by
sclerotic secondaries from a primary
adenocarcinoma of the prostate.
(b) vertebrae from the spine of a female 55.
There are extensive secondary deposits from a
primary breast cancer (green arrows).
Jaw tumours
It occurs in all races but it is more obvious in
countries that do not have a well funded
medical service.
They are slowly growing benign tumours and in
these countries they may reach a great size
before the patients have an opportunity to have
them attended to.
The tumours have areas of solid tumour and
many cystic areas.
They have a characteristic X-ray appearance
and when they are palpated they crackle – ‘egg
shell crackling.’
These features are illustrated in the following
case from Papua New Guinea.
38(a) and (b)
(a) A middle aged man from Papua New
Guinea who has an enormous ameloblastoma of
the mandible.
He complained of the weight of his jaw.
The marks on his forehead are an attempt to
relieve his pain.
(b) The X-ray shows the cystic nature of the
tumour.
39 A hemimandibulectomy specimen of an
ameloblastoma from another man from Papua
New Guinea.
It shows the characteristic appearance of solid
and cystic areas.
Very rarely amleoblastomas may be malignant.
10
Soft tissue tumours
The subtypes depend on the microscopic
appearances.
Benign and malignant
Benign soft tissue tumours.
Those to be demonstrated will be
Lipoma
Haemangioma
Diseases of synovial membrane
Synovial cyst
Lipoma
A lipoma is a local proliferation of normal
adipose tissue.
It is usually difficult to determine the margin of
a lipoma from the surrounding normal adipose
tissue.
40 This is a large lipoma that was removed
from the back of a male 61 years.
It has the characteristic yellow colour and
lobulated appearance on its cut surface.
Haemangioma
This is a benign proliferation of blood vessels,
usually small vessels.
Haemangiomas can occur in any organ and they
vary in size.
Haemangiomas are common on the skin where
they appear as small red nodules.
Occasionally they may be very large and
disfiguring and require surgical removal.
41 This is a large haemangioma that presented
as a swelling in the right buttock of a female 18
years.
It was excised by a local excision.
The cut surface shows a well circumscribed
tumour with white areas of fibrosis and
multiple blood filled channels of varying size.
The clinical and gross appearances are fairly
similar and these will be illustrated.
42 This middle aged man has a large tumour in
the medial aspect of his left thigh.
After biopsy it was treated by amputation.
43 The amputation specimen showed an
apparently well circumscribed tumour (black
arrow).
Its cut surface was mainly cream coloured with
some areas of cystic change that resulted from
necrosis of tumour.
The gross appearance of malignant soft tissue
tumours is misleading.
Very often they appear to be so well
circumscribed, as in this case, that the surgeon
thinks that they can be shelled out ‘like a pea
out of a pod.’
This is not the case because microscopic
examination invariably shows the presence of
residual tumour
They must be treated by wide excision.
44 This is another large malignant soft tissue
tumour that was removed from behind the left
knee of a female 91 years.
It has been removed by local excision ‘like a
pea from a pod.’
Its cut surface shows large areas of
haemorrhage and necrosis.
Diseases of synovial membrane
The synovial membrane is a layer of villous
like connective tissue that lines the joint surface
of the dense fibrous tissue that forms the
capsule of movable joints.
Malignant soft tissue tumours
It secretes the thick synovial fluid that
lubricates the moving surfaces of the joint.
There is a great variety of different types of
malignant soft tissue tumours and they cannot
be differentiated on gross examination.
Trauma to the joint, or infection results in an
oversecretion of synovial fluid, and the joint
becomes swollen.
11
Some pathological conditions in which there is
proliferation of the synovial tissue.
Rheumatoid arthritis which has been mentioned
already in this chapter.
Two conditions that result in proliferation of
synovial tissue, and which present with pain in
the joint – pigmented villonodular synovitis and
lipomatosis of the synovium will be illustrated.
The cyst (red arrow) has a thin lining and is
filled with thick sticky fluid like that in the
normal joint.
(b) is a thin walled cyst that was removed from
the connective tissue near the back of the knee.
It contained fluid like that of a normal joint.
It has a thin transparent wall.
It is large enough to be called a bursa.
Degenerations in the connective tissue around
joints, and actual extension of the synovium
from the joint into the adjacent connective
tissue are common.
They result in the formation of cysts that are
called ganglia (ganglion is the singular term.)
If the cyst becomes very large it is called a
bursa.
When this type of cyst is found near small
joints it is usually about the size indicated
between the two green arrows, that is about
20mm in diameter.
In that situation it is called a ganglion.
45(a) and (b)
(a) is a solid mass approximately 30mm in
length that was removed from a knee joint.
It has a well circumscribed margin, a
multilobulated appearance, some bluish areas
and a considerable amount of red pigment. (red
arrow)
Diseases of muscle
Microscopically this was a pigmented
villonodular synovitis. The pigment was
haemosiderin resulting from trauma.
Morphologically, this lesion is closely related
to a tumour of similar gross and microscopic
appearance that occurs as a small tumour found
near the wrist and ankle joints. This is called a
benign synovioma (giant cell tumour of tendon
sheath).
(b) is an infiltration of adipose tissue in the
synovial membrane of a knee joint.
This is termed synovial lipomatosis.
The patient had a painful knee and suffered
from hyperlipidaemia.
Synovial cysts (ganglia and bursae)
46(a) and (b)
(a) is a bursa in the patella tendon.
A large cyst at the back of the knee is
sometimes called a Baker’s cyst.
A student wanting to study diseases of muscle
is confronted with a myriad of different names
of the various types of muscle disease.
To add to this confusion, most of these diseases
are called after the person who described the
clinical entity.
I would like to present an introduction to a
study of diseases of muscle by first presenting a
classification according to the microscopic
appearances of the muscle in the various types
of muscle disease.
Then I will present the clinical features of the
diseases that are most frequently encountered.
Types of muscle disease
Neurogenic muscle diseases
Primary diseases affecting the motor neurons
Damage to peripheral nerves that innervate the
motor neurons.
Myopathic muscle diseases
Idiopathic, non genetic myopathies
Genetic myopathies
Myositis
Affecting a single muscle
Affecting many muscles – polymyositis
12
Affecting muscles and skin dermatomyositis
Muscle weakness associated with myotonia
Neurogenic muscle diseases
Poliomyelitis attacks the motor neurons of the
anterior horn cells of the spinal cord.
This results in paralysis of a limb for example
an arm or a leg.
Various forms of motor neuron disease.
These are idiopathic and appear in children or
in adults.
Peripheral nerve pathologies
Traumatic severance of a nerve
Peripheral neuritis
Specific infections of the nerve, for example
leprosy.
Toxic damage to nerves, for example some
medications and some industrial toxins.
Vasculitis, for example polyarteritis.
Infiltrations such as amyloid.
Idiopathic causes
Myopathic muscle diseases
Idiopathic, non genetic myopathies
These various forms of myopathy begin as
muscle weakness first occuring in later adult
life.
They have no familial or other detectable cause.
They are slowly progressive and at present
there is no specific therapy available.
Genetic myopathies
These begin in childhood.
They are progressive.
There is no specific treatment.
They usually result in death in the teenage or
early adult life.
The cause of death is respiratory failure from a
combination of weakness of the diaphragm and
respiratory infection.
The most well known example of this type of
muscle disease is pseudohypertrophic muscular
dystrophy.
Myositis
Infection in a muscle by a pyogenic organism
for example Staphylococcus aureus causes a
muscle abscess.
Polymyositis
This occurs when there is muscle weakness
affecting a number of muscles.
Causes
Autoimmune. These cases respond to steroid
therapy.
Hyperthermia. This is usually caused by over
use of muscles under adverse climatic
conditions.
This results in muscle necrosis.
Myoglobin is released from the necrotic
muscles and myoglobinuria occurs as shown by
the presence of red coloured urine.
Toxic – some medications, snake bite venom,
industrial toxins.
Dermatomyositis
In this condition there is a skin rash as well as
muscle weakness.
It may occur in adults or in children.
It is an autoimmune condition.
It responds to treatment with steroids.
I will demonstrate some of the clinical
manifestations of muscle diseases with some
illustrative cases.
Idiopathic non genetic myopathy
A 61 year old male began to have weakness of
his hands, arms and leg muscles 6 years
previously.
The weakness has slowly progressed over this
time.
47(a) and (b) These are the legs of a 61 year old
male who has one of the types of idiopathic non
genetic myopathy
In (b) note the wasting of the thigh muscles and
lower leg muscles of both legs, more marked on
the left than on the right.
The left lower leg has a tapering shape which is
characteristic of wasting of these muscles.
13
In (a) note the attitude of the left knee.
The knee joint is ‘locked’ by pushing the femur
backwards into the capsule of the knee joint.
This hyperextension of the knee is called ‘genu
recurvatum.’
Everyone who has weakness of the thigh
muscles adopts this ‘trick’ so that they can
stand up.
Note also the sagging of the left buttock which
is a result of weakness of the gluteus maximus
muscle.
All of these atrophied muscles are so weak that
he needs assistance from a spring loaded seat,
and help from his forearms to allow him to rise
from a chair.
48 The same patient as in Fig. 47 shows his
hands.
The fingers are hyperextended because the
flexor muscles of the forearms are weak, and
therefore the extensor muscles on the backs of
the forearms are overactive, causing this
excessive extension.
He is just able to form a fist by flexing the
muscles of the right hand but he cannot make a
proper fist with his left hand.
The extent of the weakness of all of these
muscles can be tested by appropriate clinical
tests.
Genetic myopathies
The best known and the commonest example of
this type of myopathy is pseudohypertrophic
muscular dystrophy.
It begins in infancy and is transmitted as an
autosomal X linked recessive genetic trait. So it
occurs in males and is transmitted by females.
Infants with this condition are weak from birth
and they do not pass the normal physical
milestones for movement.
Their calf muscles are enlarged and hard
because of fatty infiltration, but are weak.
Hence the name pseudo hypertrophic muscular
dystrophy.
49(a) and (b) This young boy has markedly
enlarged calf muscles. They are weak and he
has pseudohypertrophic muscular dystrophy.
(a)
(b)
50(a) and (b) This 5 year old boy has
pseudohypertrophic muscular dystrophy.
He has had progressive weakness of his
muscles from birth.
(a) He now needs to be propped up with pillows
to maintain a sitting position.
(b) When the pillows are removed he topples
over.
Death usually occurs during childhood or early
adult life because of respiratory insufficiency
from a combination of weakness of the
diaphragm and respiratory infection.
Muscle weakness associated with myotonia
The best known example of this phenomenon is
dystrophia myotonica.
This is an inherited disorder (autosomal
dominant) that appears either in childhood or in
early adult life.
It is characterized by the presence of
generalised muscle weakness.
In particular these patients show the
phenomenon of myotonia, that is the weak
muscles contract but then take some time to
relax. (for example when they shake hands,
they have difficulty in letting go.)
The myotonia can be demonstrated by striking
an affected muscle, for example the thenar
eminence of the hand, or the tongue with a
patella hammer.
The muscle contracts and then takes an
abnormal amount of time to relax – delayed
relaxation.
The patients also exhibit frontal baldness,
cataract, hypogonadism and cardiomyopathy.
14
51 This middle aged female has dystrophia
myotonica.
She has weakness of facial muscles as shown
by the lack of facial expression and ptosis of
both eyelids.
This facial appearance is sometimes called the
myotonic facies.
This stain differentiates the 2 major types of
muscle fibre.
Type 1 (slow twitch fibres) stain brown and
Type 2 (fast twitch fibres) stain black.
x10
52(a) and (b) The right hand of the lady in Fig.
51 shows the phenomenon of myotonia.
(a) The thenar eminence of her right hand is
struck with a patella hammer and the adductor
muscles contract and then take a long time to
relax. (b)
56 This is a muscle biopsy from a patient with a
myopathy.
There is marked variability in the size of the
muscle fibres, with some being very large.
53(a) and (b) This young female shows the
effect of myotonia when her tongue (a) is struck
with a patella hammer. It contracts and then
takes some time to relax (b).
57 This muscle biopsy shows the appearances
of neurogenic atrophy in which groups of fibres
in individual muscle fascicles (green arrow)
that are innervated by a single nerve fibre
become atrophied.
The fibres in the adjacent muscle fascicles are
normal.
Dermatomyositis
This condition may occur in children or in
adults.
Muscle weakness is accompanied by a skin
rash.
x10
(a) x10
(b) x20
(a)
(b)
54(a) and (b) The rash on legs and hands of a
young female who had muscle weakness as
well as this skin rash. She had dermatomyositis.
Ancillary tests in the examination of a patient
with a muscle wasting disease
58(a) and (b) This is the muscle biopsy of the
child with dermatomyositis.
It shows variation in the size of the muscle
fibres and an inflammatory infiltrate of
mononuclear cells which is associated with
necrosis of muscle fibres.
(a) x10
(b) x20
Electromyogram
Enzyme biochemistry
Muscle biopsy
Muscle biopsy
x10 ATPase enzyme stain.
55 A microscopic section of a normal muscle
stained with the enzyme stain ATPase.
It shows the muscle fibres are fairly similar in
size and shape and there is no inflammatory
infiltration.
59(a) and (b) This section comes from the
muscle of a patient like the one illustrated in
Figs.
The muscle fibres have almost all been
completely destroyed and replaced by adipose
tissue.
Some atrophic fibres can still be seen. (blue
arrow) and there are a few scattered
hypertrophied fibres. (purple arrows)
15
The muscle spindle (black arrow) which is a
stretch sensor that triggers contraction of
muscle is almost the last normal structure to be
destroyed.
This can be regarded as being an ‘end stage’
muscle.
60 A low magnification electron micrograph
view of a normal muscle fibre.
Dark Z bands (red arrows) divide each
myofibril into numerous contractile units.
EM examination is one of the routine tests
included in a muscle biopsy test.
16
Question 5:
a. Why is the bone so commonly affected by
secondary tumour deposits (metastases)?
Question 6:
How do osteoarthritis and rheumatoid arthritis
differ in their aetiologies?
E. Skin diseases
Question 1:
a. Under what circumstances would acute
osteomyelitis become chronic?
b. What main cellular changes distinguish
acute from chronic inflammation?
Question 3:
a. Why might the meningomyelocoele in 3a
have become infected?
b. What neurological complications occur in
association with meningomyelocoele?
c. What factors predispose to osteoporosis?
d. Why is the kidney important in the
regulation of calcium?
Question 4:
What are 2 complications of Paget's disease of
bone and why might they occur?
of the tibia.
There are limited specimens available of skin
diseases.
However, skin diseases can be divided into 2
main categories:
•
Inflammatory diseases;
•
Proliferative diseases (including both
benign and malignant lesions).
9.1
Inflammatory diseases
These include immunologic hypersensitivity
(dermatitis, eczema, blistering diseases etc.)
and infectious.
9.2
Skin cancers
•
Basal cell carcinoma
•
Squamous cell carcinoma
S1.861.7
•
Melanoma
S1.862.1
S1.858.4