What is patellofemoral instability?

When you bend or straighten your knee, your kneecap, or patella, glides within a small groove at the end of your thighbone, or femur. This groove is called the trochlea. With patellofemoral instability, the kneecap does not move easily up and down within this groove. Instead, it tends to push out to one side. This change in movement can cause pain and irritation to soft tissues in and around the knee joint.

What causes patellofemoral instability?

This disorder often occurs because of a structural problem in the knee, such as a shallow trochlear groove. It can also be caused by:

• Weak or tight muscles of the thigh or hip

• Foot problems

• Differences in leg length

• Problems with gait, or how you walk

• An injury to the knee

• Problems with alignment of the bones in the knee joint

• Loose ligaments

• Other problems with muscles, tendons, or ligaments

What are the symptoms of patellofemoral instability?

The main symptom of this disorder is knee pain. The pain tends to get worse with activity, like climbing stairs or kneeling. You may also have pain in your knee after sitting for a long time. Other symptoms include:

• Dull, aching pain that makes it hard to do daily activities

• Sore kneecap

• Popping or crackling sounds with movement

• Knee is unstable

• Knee joint is dislocated (the patella pops out of its location)

Over time, this disorder can lead to osteoarthritis in the knee.

How is patellofemoral instability diagnosed?

Your healthcare provider will ask about your symptoms and health history. They will also do a physical exam of your knee. They may ask you to do certain movements, like walking, jumping, or squatting. These can help your provider see how your knee is working.

To help diagnose patellar tracking disorder, your provider may also advise these tests:

• X-rays. This test uses energy beams to make images of internal tissues, bones, and organs onto film.

• CT or MRI scan. These tests make detailed images of organs and structures in the body. They can find structural problems in the knee, such as a shallow trochlear groove. They can also show joint damage.

How is patellofemoral instability treated?

Your healthcare provider will talk with you about your treatment options. They will depend on things like your age and overall health. Together, you and your provider can decide on the best treatment for you. Your treatment options may include:

• Rest. Your provider may advise resting your knee for a while to ease your symptoms. Or you may need to choose activities that put less stress on your knee.

• Medicines. Your provider may give you medicines to relieve pain and reduce inflammation.

• Ice. Your provider may recommend putting a cold pack on your knee a few times a day. It can help limit pain and swelling.

• Physical therapy. A physical therapist can help strengthen and restore movement in your knee. They can teach you exercises that build up weak muscles to help keep the kneecap in place. They can also ease pain with heat and cold.

• Taping. Putting tape around your kneecap may help stabilize the knee joint. It can help with movement and physical therapy.

• Orthotics. Your provider may advise shoe inserts. These can help keep your feet and lower leg aligned when moving.

• Surgery. If other treatments don’t work, your provider may advise surgery. Arthroscopy is one surgical option. This procedure uses special tools inserted through small cuts (incisions). With the tools, your surgeon can fix what may be affecting the movement of your kneecap.

Can you prevent patellofemoral instability?

You may be able to prevent the symptoms of this disorder by:

• Warming up before physical activity

• Doing exercises that strengthen and stretch muscles of the thigh and hip

• Wearing appropriate shoes during physical activity

• Stopping or limiting any activity that causes knee pain

• Losing weight, if needed

Key points about patellofemoral instability

• With this disorder, the kneecap does not move easily up and down within the trochlear groove.

• This disorder is often caused by a structural problem in the knee.

• The main symptom of this disorder is knee pain. The pain tends to get worse with activity, like climbing stairs or kneeling.

• Treatment may include rest, pain medicine, physical therapy, and orthotics. If these treatments don’t work, surgery may be needed.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.