knee is not simply a hinge-joint: you bend and straighten it, but
you can also turn it slightly in a twisting movement, when the knee
is bent. This rotary movement automatically accompanies the bending
and straightening movements. As you bend your knee, the shin-bone
turns inwards slightly relative to the thigh bone. As you straighten,
the shin-bone rotates outwards. You can only rotate the knee actively
and voluntarily when the knee is bent. When you bend your knee against
gravity or a resistance, the muscles at the back of the knee contracts
to perform the movement. The hamstrings do the main work of bending
the knee, but the gastrocnemius tendons help, especially if the
movement takes place against a strong resistance. When you straighten
your knee in the direction of gravity, for instance while you are
lying on your stomach, the hamstrings pay out to control the movement.
The quadriceps muscles on the front of the thigh straighten your
knee against gravity or a resistance, but they also act to control
the movement, when the knee bends in the direction of gravity's
of the knee-joint has two effects. Firstly, the knee is a very stable
joint, by virtue of its strong binding ligaments and the protective
effect of the muscles which control the joint's movements. Secondly,
the joint has quite a wide freedom of movement, because the bones
are not closely bound within their own configuration. The knee is
one of the three major joints in the leg which transmit loading
forces between one's body and the ground. Its stability helps to
keep us upright on our feet when we are standing, walking, hopping
This can arise from various causes. The knee can be affected by
a spontaneous inflammatory arthritis. Or it can be one of many joints
involved in a multiple inflammatory arthritis. Pain referred from
the hip or back may be felt as a simple knee pain. Problems in the
thigh-bone may causes knee pain. In older age, the knee, like the
hip, may be affected by osteoarthritis, or wear- and-tear degeneration.
In children, unexplained knee pain can be a sign of a very serious
hip condition, the slipped epiphysis.
Joint swelling is an important symptom in knee conditions. Because
of the complex and extensive synovial lining in the knee, the joint
may distend alarmingly, with swelling right round the joint, reaching
about seven centimetres above the knee onto the front of the thigh.
However, it can also be more subtle. You may also see a small pocket
of swelling, perhaps on one or the other side of the joint; or there
may be just a slight puffiness on the front of the joint, on either
side of the knee-cap. Swelling may occur at the back of the joint,
without any visible signs of it at the front. Joint swelling always
indicates inflammation. As in the ankle, knee swelling can be caused
by gravity bringing the fluid down from some higher tissues: the
swelling may track down from the hip joint or some part of the thigh
muscles. However, unlike the situation in the ankle, if you have
persistent swelling in the knee, which delineates the joint's shape,
it is unlikely to be gravitational swelling, and it is very likely
to mean that there is something wrong inside your knee.
If the swelling
has appeared for no obvious reason, it may indicate that you have
an inflammatory or degenerative condition. Your doctor will probably
arrange blood tests and X-rays, to decide whether this is so. If
the swelling occurs as the result of an injury to the knee, and
you are aware of having wrenched it, or fallen on the joint, it
is likely that you have damaged one or more of the knee's internal
structures, with irritation or damage to the synovial lining. The
swelling may come on at the moment of injury, or some hours afterwards.
The knee is
very prone to injury, because of its mobility and the variety of
stresses we subject it to. The most common type of traumatic injury
to the knee is the twisting or wrenching injury. This happens most
frequently when your knee is bent, while carrying your body-weight,
and you twist awkwardly or unexpectedly. Skiers and footballers
are most susceptible to this type of injury, but it can happen to
you while walking or running, if you trip and catch your foot, or
fall while turning. Any of the knee's structures may be damaged
in this type of injury. The full extent of the damage may be impossible
to assess immediately after the injury, and may only become evident
when the knee subsequently fails to recover its full function.
Damage Inside the Knee
of the knee's internal tissues can be damaged by a severe injury,
but the cartilage (menisci) and the cruciate ligaments are those
most commonly harmed in sportsmen.
The knee's soft-tissue cartilages can be damaged by pressure from
the bones of the joint when an abnormal force twists the bones against
each other unusually. In the normal way, the cartilages move slightly,
backwards and forwards, during knee movements. In this way, the
cartilages act as buffers throughout the whole movement, although
the joint surface of the thigh-bone is bigger than the receiving
surface on the shin-bone. However, with abnormal pressure, the cartilages
may be jammed between the two bones: if the bones then twist on
each other and apply a shearing stress on the cartilage, the tissue
The most common
cause is an abnormal twist in your knee while your weight is on
the leg. In each case, your knee is bent at the moment of injury.
A sudden stress with the knee bent, even when you are not standing
on the leg, can be enough to tear the cartilage. Cartilage tears
can also be caused by a sudden over- stress when your knee is straight,
for instance if you miss a drop-kick in rugby.
gives instant pain, to the extent that you may not be able to move
the knee at all, let alone take weight through your leg. Immediate
swelling will inhibit movement further, although the swelling may
not appear until some hours later, in which case the knee will feel
weak rather than stiff in the first instance. Visible swelling may
extend right round the knee, making the joint look bloated, or it
may be only a small patch, barely visible over the line of the joint.
At the moment of injury, it is impossible to tell, from the outside,
exactly how much damage has been done. First-aid for the swollen
knee must be applied. (see "treatment
of acute sports injury").
The only external
sign that you might have torn a cartilage is the so-called 'locked'
knee. More often, the knee is too painful to move immediately, and
this 'locking' feeling only becomes evident when the knee has recovered
enough for you to be moving it. Once you have applied first-aid
measures and made the knee comfortable, you must be taken for specialist
help as quickly as possible.
Once a specialist
has diagnosed a cartilage tear in the knee, there are two possible
courses of action. Either the torn part of the cartilage must be
removed surgically, or the problem must be treated with rehabilitation
only. The one certainty is that the torn cartilage will not heal,
or mend itself, naturally. If the specialist decides on immediate
surgery, it is because he deems that the torn cartilage will create
functional problems in the knee.
removal operation is called a meniscectomy. Recovery from the surgery
can take a varying time, according to individual circumstances.
It is possible to be back to full sporting activities within two
weeks of removal of the cartilage through the arthroscope.
If a specialist
decides not to remove the torn cartilage, after diagnosing the tear,
it is because he believes that the damage is slight, and the knee
can recover functionally without any need for surgery. Your leg
may be immobilized in plaster, to protect the knee, if the injury
was severe; or you may simply be given a supporting bandage to control
Cruciate Ligament Tears
The cruciate ligaments are two strong bands which bind the shin-
bone to the thigh-bone, across the centre of the knee. It takes
a strong force to damage them; they can be torn in a severe twisting
injury, for instance in a blocked kick or a sliding fall in a tackle
during football; or by excessive pressure forcing the knee to 'bend
backwards' when it is straight, for instance if an opponent falls
across your extended leg in rugby or hockey.
A major shearing
force can tear both cruciates together, usually tearing one or both
of the cartilages at the same time. A moderate injury may tear one
of the cruciates completely, without damaging the second, and with
or without accompanying cartilage damage. At the moment of injury,
it is totally impossible to assess the extent of the internal damage
through outward signs. The only certainty is that, if your knee
has swollen painfully, some of its internal structures have been
damaged. If you do not have an accurate diagnosis at the time of
injury, it may only become apparent that the cruciate ligaments
have been damaged much later when you have started doing sport again.
Then you may find that in certain positions your knee feels loose
and unstable. It may feel as though it is 'rolling' on itself, backwards
or forwards, usually giving a 'clunking' sound, with a sharp pain.
This makes running and turning difficult. This unstable feeling
is an external indication that there is some damage to the cruciates.
If your knee locks as well, then there is also likely to be cartilage
At the moment
of injury, the knee should be made comfortable in applying the first-aid
measures for the swollen knee. It is essential to obtain a specialist
opinion as quickly as possible. If the surgeon finds that both cruciate
ligaments are completely torn, he will probably perform an immediate
operation to try to repair the damage. If there is partial damage
to one or both of the cruciates, the surgeon will choose whether
to operate, or whether to allow the knee to recover enough for you
to resume sport, and see whether there is any residual disability
when you use the knee.
repair is done straight away, or after residual disability has shown
up, there are various methods which the surgeon may choose to mend
the damage. Some procedures involve mending the cruciates themselves,
either by re-attaching a torn end to the bone from which it has
snapped off, or by replacing the whole ligament with a synthetic
substance. Other methods of stabilizing the knee involve tightening
up the capsule and tissues around the joint, to compensate for the
internal instability. Whichever method the surgeon chooses, rehabilitation
is a slow process; full recovery may take up to a year. It is vital
to follow the surgeon's rehabilitation program to the letter, as
recovery phases differ according to the particular operation done.