Skip to main content

Read Time: 6 minutes

Patellar instability describes a range of conditions where the kneecap is displaced from its normal position. It can result from sports or other injuries or develop over time due to daily activities. Patellar instability affects about 7 out of 100,000 people in the United States. People in their teens and 20s are most likely to be diagnosed with some form of the condition. It is most common in teen female athletes.

Symptoms can include pain, swelling, and problems walking or using the stairs. A person may notice a feeling that the kneecap could become displaced. Once a person has had an episode of patellar instability, there is an increased risk for a recurrence.

Physical therapists prescribe specific exercises for those experiencing patellar instability to help decrease pain, restore proper movement, increase strength, and improve function.

Physical therapists are movement experts who improve quality of life through hands-on care, patient education, and prescribed movement. You can contact a physical therapist directly for an evaluation. To find a physical therapist in your area, visit Find a PT.

Find a PT Near You!

What Is Patellar Instability?

Normally, the kneecap (patella) rests in a groove on top of the thigh bone (femur). As the knee bends and straightens, the kneecap stays in this groove as it slides up and down. Think of the groove as a train track and the kneecap as the train. Patellar instability describes a situation when the "train," or the kneecap, "comes off of the track." It can occur during movement (if the kneecap does not stay in the groove). It also can occur without movement (if the kneecap does not rest properly in the groove).

Patellar instability can result from an injury, or develop over time with daily activities.

With traumatic injury. A specific injury can force the kneecap fully out of its groove, such as a:

  • Direct hit to the knee.
  • Quick direction change while running and "cutting" in sports.

The more extreme form of this injury is called patellar dislocation. It occurs equally in males and females. After a dislocation, knee pain will limit your activity. Most often, the kneecap can return to its proper place on its own. Sometimes, however, the kneecap does not relocate on its own. If it does not, you may require a medical procedure called a reduction.

Without a traumatic injury. Patellar instability also can occur without a specific injury. In these cases, the kneecap comes part of the way out of the groove. This occurs most often in females. The kneecap is unstable and does not fully stay in the groove during everyday activities. The knee becomes more irritated and painful with repeated activity. Pain is most common when:

  • Walking on uneven terrain.
  • Going up or down stairs.
  • Rolling over in bed.

When combined, several factors can lead to patellar instability over time. Some of these can be addressed, and some cannot. They include:

  • Abnormal bone structure. A shallow or rotated groove does not provide a stable base upon which the kneecap can rest and glide.
  • Muscle weakness. The muscles around the hip and knee may not be strong enough to control the leg’s position and keep the kneecap stable.
  • Soft tissue malfunction. Ligaments and tendons hold the kneecap in place. In very flexible people, or those with prior episodes, these tissues may stretch more easily. Over time, they can become too lax (loose) and lose their ability to hold the kneecap in place. Also, if the soft tissue on the outside of the knee is too tight (due to injury, overweight, or an underlying condition), it can pull the kneecap out of the groove.
  • Poor movement patterns. Running, jumping, and landing with the knee in a bad position can make the kneecap vulnerable to this condition.

How Does It Feel?

Patellar instability causes pain and other symptoms. These can limit your ability to do daily and leisure activities.

You may experience:

  • Knee pain. This is most common when climbing or going down stairs, squatting, running, jumping, or cutting during sport activities.
  • Feeling the kneecap shift or slide out of the groove.
  • Lack of confidence in your knee’s stability. You may notice this most when walking on uneven ground, landing from a jump, using stairs, or rolling over in bed.
  • Weakness in your leg, as if your knee might give way.
  • Swelling and stiffness in the knee.

How Is It Diagnosed?

Your physical therapist will review your medical history. They will then complete a full exam of your knee. They also will examine other areas, such as the hip and foot, that might contribute to your condition. Their goal is to assess the degree of your injury and determine its cause(s) and contributing factors. This will help to determine your treatment program.

Your initial exam can include several tests. Your physical therapist may:

    • Assess the strength and mobility (movement) of your knee and kneecap.
    • Observe how you walk, step onto a stair, squat, or balance on one leg.
    • Locate the most painful area. Your physical therapist may gently press on the front, side, and back of your knee to find where it is most painful.
    • Ask you questions about your daily activities, exercise routines, and footwear. This can help to identify other factors that may contribute to your pain.

X-rays or MRIs are rarely needed to diagnose patellar instability. However, they may help to assess bone alignment and rule out other problems after a traumatic injury or repeated episodes of patellar instability

How Can a Physical Therapist Help?

You and your physical therapist will work together to develop a plan to achieve your specific goals. Based on your exam, your physical therapist will select treatment strategies and design a personalized program for your condition. Your physical therapy treatment program may include some or all of the following:

Pain management. Your physical therapist may use several pain-relief strategies. The most common one is to apply ice to the area. Often, they will provide or recommend a knee brace to hold the kneecap safely in position. Your physical therapist also may recommend that you avoid certain activities for a period of time.

Range of motion exercises. Knee motion is often limited after an injury. Your physical therapist will guide you through targeted exercises to help restore range of motion without worsening your condition.

Muscle strengthening. Improving and balancing the strength in your leg can help control kneecap stability and reduce your risk for reinjury. Your physical therapist will select safe resistance exercises for you. You may begin by doing exercises lying on a table. You then may advance to doing exercises while standing. Your physical therapist will choose the right exercises for you based on your age, physical condition, and goals.

Functional training. Once your pain eases and your strength improves, you will need to safely transition into more demanding activities. The way you move can affect the stability of your kneecap. Your physical therapist will help you build your kneecap stability and lessen your chances of reinjury. They will teach you safe, controlled movements. Your physical therapist is an expert who can design a series of activities to help you move your body correctly.

Patient education. Your physical therapist will work with you to identify and change any external factors causing your pain. This can include the type and amount of exercise you do, and your footwear. They will look at all possible personal factors and recommend improvements. They will develop a specific exercise program designed to help you return to your desired activities pain-free.

Physical therapy promotes recovery by addressing factors that you can modify. These include lack of strength, flexibility, and body control. Your physical therapist also may recommend a rest period during which you avoid activities that aggravate your knee. Afterward, they will help you gradually resume safe activities. At the right time, they will carefully guide your progression into more demanding activities.

If patellar instability remains untreated, pain will persist and may worsen, resulting in long-term difficulty.

Teen doing leg lift exercises with a physical therapist

If Surgery Is Required

Surgery may be needed for a serious tear of the medial patellofemoral ligament. A tear is most common after a traumatic injury or repeated episodes of kneecap instability. Surgery also may be recommended if your condition does not improve after several weeks of physical therapy.

The goal of surgery is to restore normal kneecap stability. Depending on your specific condition, your surgeon may:

  • Reconstruct a damaged ligament.
  • Release tight surrounding soft tissue that is pulling the knee off track.
  • Make changes to the bone alignment of the thigh and/or shin bone.

After surgery, you will receive physical therapy to:

  • Protect your healing knee.
  • Decrease pain.
  • Restore strength.

Immediately after surgery, you may be required to limit any movement of the knee to help it heal. At the right time, your physical therapist will help guide you through exercises to safely increase your knee motion. They also will address any factors that caused your knee injury, to minimize the risk of reinjury.

Your physical therapist will then help you reintroduce more challenging movements while avoiding overstraining your knee. They will help you gradually add activities such as:

  • Stair climbing.
  • Squatting.
  • More demanding activities such as sports.

They will guide you through safely adding activities into your routine without overstraining your knee.

Caution: Keep in mind that returning to activities too soon after injury often leads to lasting pain. It also can make it harder to resolve the condition. Your physical therapist will monitor your progress and recommend only those movements and activities that can safely lead to recovery.

Can This Injury or Condition Be Prevented?

Not all cases of patellar instability can be prevented. However, the best ways to prevent the condition are to:

  • Maintain muscle strength and control in your hip, leg, and ankle.
  • Pay attention to your movements. This is especially important while climbing stairs, squatting, jumping and landing, or cutting during sports.

Physical therapists understand which movements put you at highest risk for patellar instability. One of the goals of physical therapy is to educate you on proper movement techniques to keep your knee safe. They will assess how you move, and then provide the right exercises to allow you to move safely.

For athletes, this may include observing and improving the way you jump, land, pivot, and cut. For others, it may include improving the way you climb stairs or even how you sit in a chair. Your physical therapist will identify which movements to improve to minimize your risk of knee injury.

Experiencing patellar instability once increases the likelihood of reinjury in the future. To reduce this risk, a physical therapist will select exercises specific to you. Exercises to increase your strength will, in turn, help increase your stability. You also may work on improving your control when doing activities like running, cutting, and jumping. Your physical therapist can safely guide your return to activity, introducing tasks at the right time for you. They also may recommend using a brace when doing higher-level activities to reduce your risk of reinjury.

Physical therapy can reduce your risk of reinjury and help you return to your regular activities.

What Kind of Physical Therapist Do I Need?

All physical therapists are prepared through education and experience to treat various conditions, such as patellar instability. You may want to consider:

  • A physical therapist who is experienced in treating people with patellar instability or other orthopedic injuries. Some physical therapists have a practice with an orthopedic or musculoskeletal (muscle, bone, and joint) focus.
  • A physical therapist who is a board-certified clinical specialist or who completed a residency or fellowship in orthopedic or sports physical therapy. This physical therapist has advanced knowledge, experience, and skills that may apply to your condition.

You can search for physical therapists in your area who have these and other credentials by using Find a PT, a tool built by the American Physical Therapy Association.

General tips when you're looking for a physical therapist (or any other health care provider):

  • Get recommendations from family, friends, or other health care providers.
  • Ask about the physical therapist's experience in helping people with patellar instability when making an appointment.
  • Be prepared to describe how your injury occurred and your symptoms in as much detail as possible.

Is this content helpful?

Thanks for the feedback!

Thank you. Your feedback has been sent.

The American Physical Therapy Association believes that consumers should have access to information that can:

  • Help them make health care decisions.
  • Prepare them for a visit with their health care provider.

The following articles provide some of the best scientific evidence for the treatment of patellar instability. The articles report recent research and give an overview of the standards of practice both in the United States and internationally. The article titles link either to a PubMed* abstract of the article or to the free full text, so that you can read it or print out a copy to bring with you to your health care provider.

Watson R, Sullivan B, Stone AV. Lateral patellar dislocation: a critical review and update of evidence-based rehabilitation practice guidelines and expected outcomes. JBJS Rev. 2022;10(5). Article Summary in PubMed.

Munim M, Smith N, Smith TO, et al. Clinical outcomes after the nonoperative management of lateral patellar dislocations: a systematic review. Orthop J Sports Med. 2018;6(6):2325967118766275. Article Summary in PubMed.

Sanders TL, Pareek A, Hewett TE, et al. High rate of recurrent patellar dislocation in skeletally immature patients: a long-term population-based study. Knee Surg Sports Traumatol Arthrosc. 2018;26(4):1037–1043. Article Summary in PubMed.

Christensen TC, Sanders TL, Pareek A, et al. Risk factors and time to recurrent ipsilateral and contralateral patellar dislocations. Am J Sports Med. 2017;45(9):2105–2110. Article Summary in PubMed.

Ries Z, Bollier M. Patellofemoral instability in active adolescents. J Knee Surg. 2015;28(4):265–277. Article Summary in PubMed.

Smith TO, Song F, Donell ST, Hing CB. Operative versus non-operative management of patellar dislocation: a meta-analysis. Knee Surg Sports Traumatol Arthrosc. 2011;19(6):988–998. Article Summary in PubMed.

*PubMed is a free online resource developed by the National Center for Biotechnology Information. PubMed contains millions of citations to biomedical literature, including citations in the National Library of Medicine's MEDLINE database.