Understanding Knee (Patellofemoral) Instability

Patellofemoral instability happens when the kneecap (patella) doesn’t stay in the right place and moves out of its groove in the thigh bone. This can cause knee pain, swelling and make the knee feel unstable. For people who are very active or play sports, it can be a real problem. But you can return to your regular activities by knowing what causes this condition, how to spot it, and what to do about it.

What is Patellofemoral Instability?

The patella, or kneecap, is a small bone in front of your knee. It works with the thigh bone (femur) to help your leg extend. When you have patellofemoral instability, the patella doesn’t move in the femur groove like it should. Instead, it shifts out of place – fully (dislocation) or partially (subluxation).

Causes and Risk Factors

Some things that can cause patellofemoral instability include:

  • Injury: Sometimes, a hard hit or an awkward twist to the knee can force the patella out of its groove. This might happen during a sports game, a fall, or a car accident. The impact can stretch or tear the ligaments that hold the patella in place, causing it to dislocate. After this happens once, the ligaments can weaken, making it easier for the patella to move out of place again.
  • Born with it: In some people, the groove in the femur where the patella sits is naturally shallower. A person is born with this and can’t be changed. A shallow groove doesn’t hold the patella as securely, making it easier for the kneecap to slip out of place. This can lead to patellofemoral instability even without a specific injury.
  • Loose ligaments: Ligaments are tough, flexible tissues that connect bones to each other. Some naturally have more flexibility and are ‘looser’ ligaments than others. While this can sometimes be an advantage in certain activities like gymnastics or dance, it can also mean that joints are less stable. In the case of the knee, if the ligaments can’t hold the patella firmly in place, it can be more likely to move out of its groove.
  • Weak muscles: The muscles at the front of your thigh, known as the quadriceps, play a crucial role in stabilizing the knee. These muscles help control the movement of the patella, keeping it in its groove when you bend and straighten your leg. If these muscles are weak, they might be unable to hold the patella in place effectively. This is why strengthening exercises are often a key part of treatment for patellofemoral instability.

Symptoms and Diagnosis

Common signs of patellofemoral instability are:

  • Pain when you bend your knee is one of the most common symptoms. You might feel a sharp pain or a dull ache in the front of your knee, especially when you bend it. This can make everyday activities like climbing stairs, kneeling, or even sitting for long periods difficult.
  • Swelling: After a dislocation or a spell of instability, you might notice that your knee has swollen up. This happens because the soft tissues around your knee get irritated or injured, causing fluid to build up. The swelling can last for a few days or even a few weeks.
  • Feeling like your knee is giving out: Some people describe this as a sensation of their knee ‘giving way’ or ‘buckling.’ This happens when the patella slips out of its groove, and the knee suddenly can’t support your weight like it usually does. This might make you feel unsteady or even cause you to fall.
  • Trouble walking or running: Because of the pain, swelling, and instability, you might find it hard to walk or run as you normally would. You might limp or avoid putting weight on your affected leg.

If you notice any of these signs, it’s important to get checked out by Dr. Howard as soon as possible. He will do a physical examination, checking how your knee looks and feels and how it moves.

He may also order imaging tests like X-rays or an MRI. An X-ray can show if the patella is out of place or if there’s any damage to the bones. An MRI gives a more detailed picture and can show damage to soft tissues like muscles, ligaments, and cartilage. These tests help your doctor understand what’s causing your symptoms and decide on the best treatment plan.


Treatment for patellofemoral instability varies depending on your symptoms’ severity, physical needs, and lifestyle. Below are some common treatments:

  • Physical Therapy: This is usually the first step in treatment. A physical therapist can guide you through specific exercises designed to strengthen the muscles around your knee, particularly your quadriceps. These exercises help improve your knee’s stability and control your kneecap, reducing the chance of it slipping out of place. Besides strengthening exercises, physical therapy can include flexibility exercises, balance training, and techniques to control pain and swelling.
  • Bracing or Taping: Your doctor may recommend using a brace or tape to support your knee while healing. A brace is a supportive device that you wear around your knee. It helps keep the patella aligned and reduces the strain on your knee as you move. Taping uses strips of sticky tape applied in a particular way to the knee to help keep the patella in place. Both bracing and taping can also give you a sense of security as you return to your normal activities.
  • Surgery: In some cases, especially if your patella keeps moving out of place despite other treatments, you might need surgery. Several types of surgery can help. For example, the surgeon might reposition a ligament to hold the patella in place better, deepen the groove that the patella moves in, or remove any damaged knee parts. The aim of surgery is to improve the alignment and stability of your knee, reduce your pain, and help you get back to your normal activities.

Working closely with your doctor to find the right treatment is important. Everyone’s situation is different, and what works best for you will depend on many factors, including the cause of your instability, your symptoms, and your personal goals.


You can’t prevent all cases of patellofemoral instability, but some things can lower your risk:

  • Regular Exercise: Strengthening your leg muscles, especially your quadriceps, can help keep your knee stable.
  • Proper Technique: Using the right moves when you play sports or lift heavy things can help prevent injury.
  • Safety Gear: Wearing knee pads or braces during higher-risk activities can give your knee more support.

Contact Us

Patellofemoral instability can be a big problem, but you can handle it with the proper knowledge and help. Knowing what causes it, spotting the signs, getting a diagnosis, and following the right treatment plan can greatly help.

Do not delay care if you have been experiencing instability in the knee or other joints. Dr. Peter Howard can help you secure the treatment necessary to regain mobility. Contact us today!