You walk up stairs; your knees hurt. You kneel in the garden; your knees hurt. Even after just sitting for a long time, your knees hurt. What's going on? Your knees may be telling you that it's time to take a break.

The cartilage under your kneecap (patella) is a natural shock absorber. But it doesn't come with a lifetime guarantee. Overuse, injury or other factors may lead to a condition known as chondromalacia patella — a general term indicating damage to the cartilage under your kneecap. A more accurate term for chondromalacia patella is patellofemoral pain.

Simple treatments — such as rest and ice — often help, but sometimes you may need physical therapy or even surgery to ease patellofemoral pain.

Signs and symptoms of patellofemoral pain include:

• A dull, achy pain in the front of your knee
• Increased pain when you walk up or down stairs (the most common symptom)
• Pain in your knee when kneeling or squatting
• Knee pain after sitting for long periods of time
• A grating or grinding sensation when you extend your knee
• Knee stiffness

When to see your doctor
If the knee pain isn't severe or disabling, treat it yourself with rest and cold packs. If the pain doesn't improve within a few days, consult your doctor.

Seek medical care immediately if:

• Your knee hurts and doesn't function properly after an injury
• Your knee hurts, even when you're not putting weight on it
• You have knee pain after a popping sound or snapping sensation
• Your knee locks rigidly in one position, or your kneecap is visibly out of place
• Your knee seems unusually loose or unstable when you put weight on it
• Your knee is swollen
• The pain is associated with fever, chills or redness around the joint

In adolescents and young adults, patellofemoral pain often is caused by muscle weakness, overuse or injury. Sometimes an unusual alignment of the kneecap is responsible. For older adults, patellofemoral pain may be related to arthritis of the knee joint — which causes cartilage to lose its normal shock-absorbing ability. Weak thigh and hip muscles or flat feet also may contribute to the pain. Even something as simple as worn-out or ill-fitting shoes can contribute to patellofemoral pain.

Runners and other people who routinely do a lot of exercise involving their lower legs may have a greater risk of developing patellofemoral pain. And, women are more likely to develop this condition than are men.

Other risk factors for developing patellofemoral pain include:

• Weakness of hip muscles, especially the muscles on the outside of the hip (hip abductors)
• Malalignment of the lower extremity
• Trauma to the kneecap, such as a dislocation or fracture
• Wearing worn-out shoes or shoes that don't fit properly

Patellofemoral pain can lead to difficulty with routine activities, such as squatting and climbing stairs.

You're likely to start by first seeing your family doctor or a general practitioner. However, in some cases, you may be referred to a physical therapist, an orthopedic surgeon or a sports medicine specialist.

Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, as well as any vitamins or supplements, that you're taking.
• Take copies of any imaging tests you've had done, such as an X-ray, MRI or CT scan, or arrange to have these test results sent to your doctor before the appointment. Ask your doctor's staff the best way to do this when making your appointment.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out. For patellofemoral pain, some basic questions to ask your doctor include:

• What is likely causing my symptoms?
• Are there any other possible causes for my symptoms?
• What kinds of tests do I need? How do I prepare for these tests?
• Is my condition likely temporary or chronic?
• What are my treatment options?
• What is the best course of action?
• Are there any alternatives to the primary approach that you're suggesting?
• Are there any restrictions on activity that I need to follow?
• How long do I need to restrict activity?
• Are there any exercises I can do at home that might help?
• Is there anything else I can do that will help ease my symptoms?
• Should I see a specialist? What will that cost, and will my insurance cover seeing a specialist?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions if don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous, or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

What you can do in the meantime
The first thing you need to do is rest, and stop participating in any activity that causes you pain. Applying ice to the injured area and elevating your knee may help. If needed, take acetaminophen (Tylenol, others) or nonsteroidal anti-inflammatory pain relievers, such as aspirin or ibuprofen (Advil, Motrin, others), until you can get in to see your doctor.

Diagnosis is based primarily on your symptoms and a physical exam. Tell your doctor about your typical activities and any recent changes to your routine. To gauge your knee's strength and alignment, your doctor may ask you to walk, jump, squat or move your knee in certain ways. He or she may detect tenderness or feel a grinding sensation below your kneecap when you extend your knee.

Your doctor may recommend X-rays or other imaging tests, such as an MRI or CT scan, to help determine the cause of your knee pain. If your symptoms are severe, a minor surgical procedure known as arthroscopy may be helpful in treating this condition.

Treatment of patellofemoral pain often begins with simple measures:

• Rest your knee as much as possible.
• Avoid any activities that increase the pain, such as climbing stairs.
• If needed, take pain relievers such as acetaminophen (Tylenol, others) or nonsteroidal anti-inflammatory pain relievers, such as aspirin or ibuprofen (Advil, Motrin, others).

Exercises and therapy
To promote your recovery, your doctor may recommend specific exercises or physical therapy to strengthen the muscles that support your knees and control limb alignment, such as your quadriceps, hamstrings and the muscles around your hips (especially the hip abductors). In other cases, knee braces or arch supports may be recommended.

When you exercise, choose activities that go easy on your knees, such as bicycling and swimming. Your physical therapist may show you how to tape your knee to reduce pain and enhance your ability to exercise. You may be able to return to activities such as running, but you may need to reduce the number of miles you run until it doesn't hurt during or after exercise. Icing after exercise may be especially helpful.

Don't rush back to activity, however. It can take six weeks or more before you begin to feel better.

Types of surgery
If these measures aren't effective, in rare cases surgery may be an option.

• Arthroscopy. During this procedure, the doctor inserts an arthroscope — a pencil-thin device equipped with a camera lens and light — into your knee through a tiny incision. Surgical instruments are passed through the arthroscope to remove fragments of damaged cartilage.
• Realignment. In more severe cases, a surgeon may need to operate on your knee to realign the angle of the kneecap or relieve pressure on the cartilage.

Sometimes knee pain just happens. But certain steps may help prevent the pain.

• Maintain strength. Strong quadriceps and hip abductor muscles help keep your knee balanced during activity.
• Think alignment and technique. Ask your doctor or physical therapist about flexibility and strength exercises to optimize your technique for jumping, running and pivoting — and to help the patella track properly in its groove. Especially important is exercise for your outer hip muscles to prevent your knee from caving inward when you squat, land from a jump, or step down from a step.
• Lose excess pounds. If you're overweight, losing the extra weight relieves stress on your knees.
• Warm up. Before running or any other exercise, warm up with five minutes or so of light activity.
• Stretch. Promote flexibility with gentle stretching exercises.
• Increase intensity gradually. Avoid sudden changes in the intensity of your workouts.
• Practice shoe smarts. Make sure your shoes fit well and provide good shock absorption. If you have flat feet, consider shoe inserts.

It's also important to listen to your body. If your knee hurts, stop what you're doing. Pushing yourself may only lead to injury.