Knee pain is a common complaint that affects
people of all ages. Knee pain may be the result of an injury, such as a
ruptured ligament or torn cartilage. Medical conditions including arthritis,
gout and infections also can cause knee pain.
Many types of minor knee pain respond well to
self-care measures. Physical therapy and knee braces also can help relieve knee
pain. In some cases, however, your knee may require surgical repair.
Symptoms
The location and severity of knee pain may
vary, depending on the cause of the problem. Signs and symptoms that sometimes
accompany knee pain include:
- Swelling and stiffness
- Redness and warmth to the touch
- Weakness or instability
- Popping or crunching noises
- Inability to fully straighten the knee
Causes
Knee pain can be caused by injuries,
mechanical problems, types of arthritis and other problems.
Injuries
A knee injury can affect any of the
ligaments, tendons or fluid-filled sacs (bursae) that surround your knee joint
as well as the bones, cartilage and ligaments that form the joint itself. Some
of the more common knee injuries include:
- ACL injury. An ACL injury is the tearing of the anterior cruciate
ligament (ACL) — one of four ligaments that connect your shinbone to your
thighbone. An ACL injury is particularly common in people who play
basketball, soccer or other sports that require sudden changes in
direction.
- Torn meniscus. The meniscus is formed of tough, rubbery cartilage
and acts as a shock absorber between your shinbone and thighbone. It can
be torn if you suddenly twist your knee while bearing weight on it.
- Knee bursitis. Some knee injuries cause inflammation in the bursae,
the small sacs of fluid that cushion the outside of your knee joint so
that tendons and ligaments glide smoothly over the joint.
- Patellar tendinitis. Tendinitis is irritation and inflammation of
one or more tendons — the thick, fibrous tissues that attach muscles to
bones. Runners, skiers, cyclists, and those involved in jumping sports and
activities are prone to develop inflammation in the patellar tendon, which
connects the quadriceps muscle on the front of the thigh to the shinbone.
Mechanical
problems
Some examples of mechanical problems that can
cause knee pain include:
- Loose body. Sometimes injury or degeneration of bone or cartilage
can cause a piece of bone or cartilage to break off and float in the joint
space. This may not create any problems unless the loose body interferes
with knee joint movement, in which case the effect is something like a
pencil caught in a door hinge.
- Iliotibial band syndrome. This occurs when the ligament that extends
from the outside of your pelvic bone to the outside of your tibia
(iliotibial band) becomes so tight that it rubs against the outer portion
of your femur. Distance runners are especially susceptible to iliotibial
band syndrome.
- Dislocated kneecap. This occurs when the triangular bone (patella)
that covers the front of your knee slips out of place, usually to the
outside of your knee. In some cases, the kneecap may stay displaced and
you'll be able to see the dislocation.
- Hip or foot pain. If you have hip or foot pain, you may change the
way you walk to spare these painful joints. But this altered gait can
place more stress on your knee joint. In some cases, problems in the hip
or foot can refer pain to the knee.
Types of
arthritis
More than 100 different types of arthritis
exist. The varieties most likely to affect the knee include:
- Osteoarthritis. Sometimes called degenerative arthritis,
osteoarthritis is the most common type of arthritis. It's a wear-and-tear
condition that occurs when the cartilage in your knee deteriorates with
use and age.
- Rheumatoid arthritis. The most debilitating form of arthritis,
rheumatoid arthritis is an autoimmune condition that can affect almost any
joint in your body, including your knees. Although rheumatoid arthritis is
a chronic disease, it tends to vary in severity and may even come and go.
- Gout. This type of arthritis occurs when uric acid crystals build up
in the joint. While gout most commonly affects the big toe, it can also
occur in the knee.
- Pseudogout. Often mistaken for gout, pseudogout is caused by
calcium-containing crystals that develop in the joint fluid. Knees are the
most common joint affected by pseudogout.
- Septic arthritis. Sometimes your knee joint can become infected,
leading to swelling, pain and redness. There's usually no trauma before
the onset of pain. Septic arthritis often occurs with a fever.
Other problems
Chondromalacia patellae (patellofemoral pain
syndrome) is a general term that refers to pain arising between your patella
and the underlying thighbone (femur). It's common in athletes; in young adults,
especially those who have a slight misalignment of the kneecap; and in older
adults, who usually develop the condition as a result of arthritis of the
kneecap.