When your kneecap slips out of its groove, it’s not just painful. It can really slow you down and bring risks that go way beyond those first few hours or days of pain and swelling. The more you understand about this injury, the better your decisions about treatment and recovery will be.
What Actually Happens in a Patella Dislocation?
When the patella pops out and moves off to the side of the knee (patella dislocation) it’s usually because of a sudden twist, a direct hit while your knee is bent, or sometimes because of natural factors in your anatomy that make your kneecap less stable. A patella dislocation means the kneecap has come all the way out of its groove, while subluxation means it only partially slips out and may quickly go back into place. Both can be painful and cause joint damage. These injuries often affect adolescents and young adults, particularly females and those active in pivoting sports.
When this happens, you’ll notice it right away. The shape of your knee looks different, it swells up fast, and straightening your leg can be next to impossible. Even if the kneecap slips back into place quickly, you might be dealing with hidden damage that needs attention.
If you think your kneecap is dislocated, don’t force it back into place on your own. Rest your leg and try to straighten it if possible, and use a cold pack to help with pain and swelling. Seek medical attention promptly if it doesn’t reduce on its own. Imaging and a thorough exam are needed within a week or so to confirm that there wasn’t additional damage done to the knee.
What Happens Right After a Patella Dislocation?
Some people think a kneecap dislocation is a simple fix, but it nearly always hurts important tissues in your knee and needs a real management plan. The occurrence of patella dislocation signals a traumatic force strong enough to tear the medial patellofemoral ligament (MPFL), the primary soft tissue stabilizer that prevents the kneecap from shifting laterally.
A kneecap dislocation always injures the MPFL, and often results in bruising of the bone and possible cartilage injury.
Common immediate consequences include:
- Tearing of the MPFL.
- Bone bruising along the lateral femur and medial patella.
- Cartilage damage, sometimes significant enough to require surgery.
- Swelling and joint effusion (a swollen joint).
- Instability and loss of confidence in the affected knee.
- Acute pain and loss of function. Sometimes you may need crutches at first and/or a brace to help you walk.
After your first patella dislocation, I almost always suggest an MRI. It helps us spot cartilage damage and anatomic abnormalities you can’t see from the outside, and shapes the best plan for getting your knee back to normal. After the first few days, your provider should start gentle motion and physical therapy unless there is a significant loose fragment. This transition helps restore movement, build strength, and protect your knee as you heal.
Why Is Future Instability a Concern?
This isn’t always a one-time event. At least one third of people who skip surgery have another kneecap dislocation, and some individuals have a higher risk of repeat dislocations (up to 88%), depending on their unique knee anatomy or activity level.
Recurring patellar dislocation risk is especially high if you are young, female, or have certain anatomical risk factors such as:
- Shallow trochlear groove (trochlear dysplasia)
- High-riding kneecap (patella alta)
- Increased lateral pull on the patella (elevated TT-TG distance)
- Ligamentous laxity or generalized hypermobility
Published studies show between 33-88% of patients will experience another dislocation, sometimes more, without corrective intervention. Each repeat dislocation increases the chance of more joint damage and early arthritis.
Can You Prevent Another Dislocation?
The best way to protect your knee is to strengthen your thigh, hip, and core muscles with exercises prescribed by your physical therapist. They may recommend a brace for certain activities. You can also modify your workouts to avoid sudden twists or direct impacts to reduce your risk.
Cartilage Injury and Early Arthritis
A lesser-known but major consequence of kneecap dislocation/patella dislocation is the potential for cartilage injury. The shearing force of dislocation often scrapes the cartilage surface of the kneecap or the underlying femur, sometimes dislodging fragments into the joint (osteochondral fracture). Even a single event can accelerate cartilage breakdown, raising the risk for early arthritis in the patellofemoral joint, especially if instability or further dislocations occur.
If imaging shows loose bone or cartilage, surgery is often indicated to retrieve or repair these fragments, and decisions about ligament reconstruction versus nonoperative care become more urgent.
Recovery and the Psychological Toll
It’s not just about ligaments and cartilage, either. This injury can really shake your confidence, especially if you’re active. Many of my patients worry about their knees giving out again, and rehab is just as much about rebuilding trust as it is about strength.
A detailed, supervised rehabilitation program addresses both strength and confidence, but the risk of reinjury can still alter people’s lifestyle and activity choices. Understanding exactly what happened and how to resolve it, as well as recovery timelines, can help you return to an active lifestyle with confidence. Most people start gentle movement in the first week. Return to full activity can take several months and depends on the degree of injury or surgery performed.
When Is a Patella Dislocation Most Serious?
- You’re dealing with large loose fragments in the joint.
When a dislocation knocks off a chunk of bone and/or cartilage, those loose pieces can get stuck, causing pain, swelling, and locking in the knee. These often need surgery to remove or repair, since leaving them alone can increase the risk of long-term damage or accelerated arthritis. - Your kneecap doesn’t pop back into place on its own.
Normally, most patella dislocations reduce spontaneously or with gentle straightening before patients get to the ER. If your kneecap is stuck and can’t be relocated, it might be trapped by tissue, bone fragments, or damage inside the joint, which always requires prompt attention. - The knee gets stuck and won’t extend.
If your knee can’t straighten fully after a dislocation, it may be because of mechanical blockage from a loose fragment or significant swelling inside the joint. This calls for urgent imaging and often aspiration to remove the fluid in the knee to restore normal motion. - You’ve had several episodes, or you have high-risk anatomy.
If patella dislocation has happened more than once, or you have factors like a shallow trochlear groove, a high-riding patella, and/or ligamentous laxity, you’re at much higher risk for repeated instability. Each repeat event can worsen cartilage or bone damage, increasing the risk of early arthritis. - You’re a high-level athlete worried about getting back to your sport.
Athletes place greater demands on their knees, and recurrent instability or delay in restoring normal function can threaten both performance and long-term knee health. Early, targeted treatment (sometimes surgical) can be important for protecting the joint and supporting return to play at your level.
Each of these scenarios warrants close evaluation with an orthopedic specialist, and often consideration of surgical intervention (such as MPFL reconstruction surgery) to restore knee stability and protect your joint health.
More Than a Temporary Setback
A patella dislocation is a serious injury because even a single event creates significant damage to the ligament and can set the stage for long-term instability, repeat injuries, and degenerative joint changes. Accurate assessment, including imaging, and creating a management plan that addresses both the initial injury and any underlying anatomical risk factors are essential for you to achieve the best long-term outcome.
If you (or someone close to you) have had a kneecap dislocation, don’t wait. Getting the right orthopedic evaluation as soon as possible helps protect your knee for the long haul and can minimize future problems.
For additional information on knee cap dislocation and joint instability, see the American Academy of Orthopaedic Surgeons guide.
For more treatment options and recovery stories, take a look at these resources on my site:
While some people recover easily from a patella dislocation, don’t underestimate the injury’s seriousness and its long-term impact. Getting the right treatment and follow-up care can make all the difference in returning to full activity and avoiding future problems. Regular check-ins with your orthopedic team are important to track your progress and adjust your recovery plan if needed. Have questions? Please reach out.
(Image generated with AI.)