Knee Injuries and Disorders
Introduction
The knee lets the leg bend and straighten. It also provides support for the body. Knee
problems can cause pain and difficulty walking. There are many injuries and disorders
that can affect the knee.
Treatment for knee injuries and disorders depends on the cause. Treatment may
include medicine, surgery or other treatments.
This reference summary will help you understand injuries and disorders that affect the
knee. It covers common injuries and disorders of the knee, as well as treatment
options.
The Knee
The knee is the largest joint in the body. It connects
the thigh bone to the shin bone. The thigh bone is
also called the femur. The shin bone is also called
the tibia.
The patella is also included in the knee joint. The
patella is a floating bone that gives the knee its
round shape. These bones are covered by special
tissue called cartilage or meniscus. The smooth
surface of the meniscus allows for smooth and
painless movement at the knee joint.
Thigh Bone
Patella
Synovium
Shin Bone
Between the two pieces of cartilage in a joint, there is a little bag lined by special
tissue. The tissue is known as synovium. The synovium secretes fluid that helps
lubricate the joint.
Tendons in the knee connect muscles of the leg to bone. Muscles and tendons help
the knee joint move. The knee joint allows the leg to bend up and down only, not side
to side.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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Ligaments connect the bones in the knee joint and help stabilize the knee. They
protect the knee from going sideways and getting injured. Two ligaments are located
on the sides of the knee. These are called the medial collateral ligament, or MCL, and
the lateral collateral ligament, or LCL. There are also two ligaments in the center of the
knee that cross each other. These are called the anterior cruciate ligament, or ACL,
and the posterior cruciate ligament, or PCL.
Even though the joint allows movement, the muscles of the legs perform the actual
motion.
Symptoms
Many knee injuries and disorders have similar symptoms. The main
symptoms are pain and swelling in or around the knee joint. The pain
may be dull or more severe. It can get worse when doing certain
activities, such as climbing stairs or straightening the knee. In some
cases, the pain may be relieved by rest.
Other common symptoms of knee injuries and disorders are:
• A knee that locks or buckles.
• A stiff knee.
• Clicking or popping noises from the knee.
• Weakness in the knee.
Some knee injuries and disorders may also cause:
• A knee that is red and warm to the touch.
• A tender, bony bump below the kneecap.
• Difficulty bending, extending or lifting the leg.
Talk to your health care provider if you notice any of these symptoms or other
changes. Finding a problem early makes treatment easier in most cases.
Arthritis
Arthritis is the most common disease that affects the knees. The cartilage in the knee
gradually wears away. This causes pain and swelling. There are many types of
arthritis. Almost all types of arthritis can affect the knee. The following types are the
most common.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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Osteoarthritis is due to chronic wear and tear. The cartilage wears away and causes
changes to the bone. It is more common in older people. Post-traumatic arthritis is due
to trauma to a joint. Trauma may happen during a car accident or a sports injury, for
example.
Rheumatoid arthritis involves swelling, redness and tenderness in the joint. It is an
autoimmune disease. This means the immune system attacks parts of the body. In
rheumatoid arthritis, the synovium is attacked and becomes inflamed. This leads to the
destruction of the synovium as well as the underlying joint.
Other rheumatic diseases can also affect the knee joint. These
include:
• Ankylosing spondylitis.
• Gout.
• Infectious arthritis.
• Lupus.
• Psoriatic arthritis.
Ankylosing spondylitis is an inflammatory type of arthritis. It
primarily affects the spine but can also affect the knee. Gout is
a very painful type of arthritis. It happens when crystals of uric
acid build up in the joints. Uric acid is a waste product of the body. Infectious arthritis is
an infection in the joint. The infection comes from a bacterial, viral or fungal infection
that spreads from another part of the body.
Lupus is an autoimmune disease. This means the immune system attacks healthy cells
and tissues by mistake. Lupus can cause many symptoms, including joint pain or
swelling. Psoriatic arthritis is a type of arthritis that often happens with psoriasis.
Psoriasis is a skin disease. It causes itchy or sore patches of thick, red skin with silvery
scales.
Unfortunately, there is no cure for most types of
arthritis. But arthritis can be slowed and controlled.
Medicines can decrease inflammation in the body.
Physical therapy can help keep joints affected by
arthritis in shape. Splints are commonly used to
prevent, slow down or make up for joint deformities.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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If other treatments are unsuccessful, surgery may be done. The type of surgery
depends on the type of arthritis. In severe cases, a knee replacement surgery can be
done. It involves removing damaged parts of the joint and replacing those parts with
man-made materials.
Ligament Injuries
Ligament injuries are common in sports. Two ligaments in
the knee that are commonly injured are the ACL and
PCL. These ligaments are in the center of the knee. The
ACL is often injured by a sudden twisting motion. This
may cause the ACL to tear. The PCL is often injured by a
direct impact. This could be caused by a car accident or
football tackle.
The MCL and LCL may also be injured. The MCL runs along the inside of the knee
joint. The LCL runs along the outside of the knee joint. The MCL and LCL may be
injured by a blow to the outer side of the knee. This can happen in sports, such as
football or hockey. The ligaments may be sprained or they may tear.
A ligament injury may cause your knee to swell. This can make walking painful. Your
knee may also feel unstable. Right after the injury happens, ice packs may be used to
reduce swelling. Physical therapy and rehabilitation use exercises to help restore the
knee to its pre-injury condition. Sometimes a knee-brace is used to give the knee
support. Surgery may be done for more severe injuries. It may also be done if the
patient wants to return to sports that put a high demand on the knees.
Cartilage Injuries and Disorders
Cartilage covers the bones in the knee joint. It allows for smooth and painless
movement at the knee joint. When cartilage is injured or damaged, the knee does not
move as smoothly. This can cause pain when moving or straightening the knee joint. It
can also cause the knee to lock or make a clicking noise. The most common problems
involving cartilage are arthritic issues discussed earlier. The rest of this section is about
the other problems that can affect cartilage.
Chondromalacia is a disorder that affects the cartilage of the kneecap. It causes the
cartilage under the kneecap to soften. This lets the kneecap rub against the thigh
bone. Eventually the cartilage may be worn away.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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Chondromalacia is more common in young adults. It can be caused by:
• Injury.
• Misalignment of the kneecap.
• Overuse of the joint.
• Weak muscles around the hip and knee.
The meniscus may also be injured. The meniscus is a
C-shaped piece of cartilage. It acts like a cushion
between the thigh bone and shin bone. The meniscus
is easily injured if the knee is twisted while supporting
weight. When injured, the meniscus may tear. If the tear is small, the meniscus stays
connected to the front and back of the knee. If the tear is large, the meniscus may only
be connected by a small thread of cartilage.
Treatment for cartilage injuries and disorders often includes exercises to strengthen
muscles. The exercises focus on muscles around the hip and knee. Exercises may
include:
• Riding a stationary bicycle.
• Swimming or exercising in a pool.
• Using a cross-country ski machine.
Electrical stimulation may be used to treat cartilage injuries and disorders. It can help
strengthen muscles.
For more severe injuries, surgery may be needed. During surgery, cartilage fragments
can be removed. Any tears or other types of damage can be repaired as well.
Tendon Injuries and Disorders
Tendons connect muscle to bone. There are three main types
of tendon injuries and disorders that can affect the knee. These
include:
• Tendinitis and ruptured tendons.
• Osgood-Schlatter disease.
• Iliotibial band syndrome.
Tendon
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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Tendinitis is inflammation of a tendon. A ruptured tendon is when a tendon tears.
These problems may be caused by:
• Overusing a tendon. This may be caused by playing certain sports.
• Trying to break a fall. This is more likely to happen in older people.
If a tendon is overused, it stretches and can become inflamed. One example of
tendinitis is called “jumper’s knee.” It affects the lower tendon of the kneecap. This
tendon is called the patellar tendon. “Jumper’s knee” happens in sports that require a
lot of jumping. One example of a sport that requires jumping is basketball.
Treatment for tendinitis often involves resting and elevating the joint. Applying ice and
taking NSAID medicines can help reduce swelling. Exercises may also be helpful.
NSAID stands for nonsteroidal anti-inflammatory drug. Some examples of these drugs
are aspirin or ibuprofen.
If a tendon ruptures, surgery can be done to reattach the ends. A cast
is worn after surgery. Crutches are used to allow the tendon time to
heal.
Osgood-Schlatter disease affects the growth area of the upper shin
bone. It is caused by repeated stress or tension to this area. The
disease often affects active young people, especially boys ages 10 to
15. Osgood-Schlatter disease may be caused by sports with a lot of
running or jumping. It is also associated with an injury where the
tendon tears away from the tibia. When the tendon tears away, it takes a piece of bone
with it.
Usually Osgood-Schlatter disease will improve without treatment. But applying ice can
help reduce inflammation. Exercises may also help strengthen the knee. Sports
activities may need to be avoided until the disease goes away.
Iliotibial band syndrome happens when a band of tissue rubs over the bone of the
knee. It may be caused by:
• Direct injury to the knee.
• Long-term overuse of the knee, especially with running.
Iliotibial band syndrome often goes away after a person reduces activity. Stretching
exercises and muscle strengthening exercises can help a person return to activities
over time. Rarely, surgery can be done to split the tendon so that it is not as tight.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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Other Knee Injuries
There are also some other common knee injuries, including:
• Osteochondritis dissecans.
• Plica syndrome.
Osteochondritis dissecans happens when part of the bone in a joint does not get
enough blood. This causes the bone and cartilage to slowly loosen. Some cartilage
may break off. It can cause sharp pain and locking of the knee joint. The main
treatment for osteochondritis dissecans is surgery. Loose cartilage fragments can be
pinned or screwed in place. Loose fragments can be reattached.
Plica syndrome affects bands of tissue in the knee called plicae. When these bands of
tissue swell, it is called plica syndrome. Plica syndrome is caused by overuse or injury.
Treatment of plicae syndrome may include:
• Ice or medicines to reduce swelling.
• Resting the joint.
• Elastic bandage on the knee.
• Exercises to strengthen muscles.
• Cortisone injections into the plicae.
• Surgery to remove the plicae if other treatments are unsuccessful.
Summary
The knee lets the leg bend and straighten. It also provides support for the body. Knee
problems can cause pain and difficulty walking. There are many injuries and disorders
that can affect the knee. These include:
• Arthritis.
• Ligament injuries.
• Cartilage injuries and disorders.
• Tendon injuries and disorders.
• Other knee injuries.
Treatment for knee injuries and disorders depends on the
cause. Treatment may include medicine, surgery or other
treatments. It may also include exercises, knee braces and
reduced activity. Talk to your health care provider if you
notice any abnormal changes or knee symptoms. Finding a
problem early can make its treatment easier.
This document is for informational purposes and is not intended to be a substitute for the advice of a doctor or healthcare professional or a
recommendation for any particular treatment plan. Like any printed material, it may become out of date over time. It is important that you rely on the
advice of a doctor or a healthcare professional for your specific condition.
©1995-2016, The Patient Education Institute, Inc. www.X-Plain.com
Last reviewed: 07/21/2016
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