Background Information on Patella Dislocation
The patella, or kneecap, is a small bone that sits in front of the knee joint. The patella is connected to the thighbone (femur) by the quadriceps tendon and helps to stabilize the knee joint. Normally, the patella glides smoothly up and down as the knee bends and straightens. The bony groove that it glides back and forth in is known as the trochlea.
However, sometimes the patella can become dislocated. This means that it slips out of place, usually to the outside of the knee. Patella dislocation occurs when the patella slides out of its normal position. This can happen if there is a sudden force applied to the knee, such as during a fall or car accident.
A dislocated kneecap is a relatively common injury, particularly among young athletes. Symptoms of patella dislocation include knee pain, swelling, and instability. Treatment typically involves wearing a brace or splint to immobilize the knee and allow it to heal. In some cases, surgery may be necessary to repair the damage.
In This Article ▼
What are Symptoms of a Dislocated Kneecap
The most common symptom of patella dislocation is knee pain. If you have a patella dislocation, you will likely feel a sharp pain in your knee. Your knee may look deformed and feel unstable. You may also have difficulty straightening your leg. You may also feel a pop or snap at the time of injury. Other symptoms include:
- Swelling
- Pain
- Instability
- Difficulty straightening the knee or inability to straighten the leg
- Tenderness around the knee joint
- Inability to bear weight on the injured leg
How does the Kneecap Dislocate (Risk Factors)
There are many components that contribute to dislocation of the kneecap. There are bony stabilizers, such as the shape of the patella and the shape of the trochlea (the groove that the kneecap slides back and forth in). There are also soft tissue stabilizes, such as the medial patellofemoral ligament (MPFL). This ligament acts as a “check rein” to keep the patella from sliding too far to the outside of the knee.
Risk Factors
Other risk factors for recurrent patella instability include things like ligamentous laxity (looseness of the connective tissues of the joints), height of the patella (patella Alta, or being too high), trochlear dysplasia (shape of the groove), knee valgus (knees bowing in, sometimes referred to as “knock knees”), femoral anteversion (rotation of the thigh bone, or femur), and position of the tibial tubercle (where the patellar tendon attaches on the tibia, or shin bone).
- Ligamentous laxity
- Patella Alta (high-riding patella)
- Trochlear Dysplasia (shallow shaped groove)
- History of repeated dislocations
- Knee valgus (“knock knees”)
- Internal rotation of the femur
- Lateralized tubercle, or increased tibial tubercle-trochlear groove distance (TTTG)
- Poor neuromuscular control
Injury Mechanism
Patella dislocation is a relatively common injury, particularly in young people. It is more common in women than men and often occurs during sports that involve sudden stops or changes in direction, such as basketball, football, volleyball, and skiing.
Video analysis has demonstrated that the typical injury mechanism for a patellar dislocation involves a flexed hip, valgus position at the knee, slightly flexed knee, and external rotation to the tibia. However, there are other varieties of knee positions that can also lead to a dislocated patella.
Dislocated Kneecap Recovery Time
Recovery from patella dislocation typically takes several weeks. Depending on the severity of the injury, return to sports is usually assessed at 6-8 weeks. It is important to follow your doctor’s instructions during this time to avoid further injury. Once the knee has healed, you will likely need to undergo physical therapy to help regain range of motion and strength. Surgical treatment is typically only necessary in severe cases where there is significant damage to the ligaments or tendons around the knee or there are recurrent dislocations. Surgical recovery time depends on the procedure(s) performed.
In general, 6 criteria are used to determine if athletes are ready to return to sport after a patellar dislocation (based on article by Ménétrey et al)
- No pain
- No effusion
- No patellofemoral instability
- Full range of motion
- Nearly symmetrical strength
- Excellent dynamic stability
Ideally, patients should be able to meet these criteria 6 weeks after a dislocation treated non-surgically, and 3-4 months after surgical treatment. However, there is considerable variability depending on the severity of the injury and the type of surgical treatment performed. For athletes recovering from other major knee injuries, the ACL surgery recovery timeline guide at Ochsner-Andrews illustrates how similar criteria-based return-to-sport benchmarks are applied across knee rehabilitation programs.
Diagnosis of Patellar Dislocation
A patella dislocation is diagnosed through a physical examination and medical history. Your doctor or health care provider will ask you how the injury occurred and whether you’ve had any previous patellar dislocations. They will also check for signs of patellar instability, such as swelling or tenderness around the knee joint. X-rays may be taken to rule out other possible causes of your symptoms, such as a fracture. In some cases, an MRI scan may be ordered to assess the damage to the ligaments and tendons around the knee joint.
Video & Discussion About Patrick Mahomes’ Patellar Dislocation
Patella Dislocation Treatment
Most patella dislocations can be treated without surgery. Treatment typically involves wearing a knee brace or splint to immobilize the knee and allow it to heal. You may also be prescribed pain medication and anti-inflammatory drugs to help reduce swelling and pain. Walking after patellar dislocation will depend on the severity of the injury and the treatment initiated.
Non-operative management
Most of the time, first-time patellar dislocations are treated non-surgically. After adequate healing time, physical therapy may be recommended to help improve range of motion and strength. The goals of physical therapy are to help reduce swelling, maintain range of motion, and strengthen dynamic stabilizers of the patella such as the quad muscle (VMO) and the glut muscles. Athletes interested in how structured rehabilitation phases are organized for knee injuries can review the phase-based ACL rehabilitation guide at Ochsner-Andrews, which illustrates the progressive loading principles that apply broadly to knee recovery. Patella dislocation exercises include:
- Eccentric and isometric quad strengthening, focusing on the vastus medialis obliquus (VMO)
- Straight leg raises
- Knee extensions
- Hip abduction exercises (lateral leg lifts) focusing on the glut medius muscle
- Core exercises such as crunches
Specific braces may be used to help push the patella more medially and keep it from subluxing or dislocating to the lateral side (outside of the knee)
Surgical Management
In some cases, surgery may be necessary to repair damage to the ligaments or tendons around the knee joint. Potential surgical procedures can include knee arthroscopy, surgery to repair the torn ligaments (MPFL repair), MPFL reconstruction, and/or tibial tubercle transfer.
Patella Subluxation: When the Kneecap Partially Slips
Patellar subluxation occurs when the kneecap shifts partially out of its normal position in the trochlear groove but does not fully dislocate. Unlike a complete dislocation where the patella displaces entirely to the outside of the knee, subluxation involves a momentary shift that often reduces on its own. Patients frequently describe a sensation of the kneecap “slipping” or “catching” during activity, particularly with pivoting, squatting, or going down stairs. The knee may feel unstable or give way, and there is often mild swelling and tenderness along the inner (medial) side of the kneecap where the medial patellofemoral ligament (MPFL) has been stretched.
Patellar subluxation shares many of the same underlying risk factors as full dislocation, including trochlear dysplasia (a shallow groove), patella alta (a high-riding kneecap), increased Q-angle, and ligamentous laxity. Damage to the MPFL, the primary soft tissue restraint preventing lateral patellar displacement, is common in both conditions. Treatment for subluxation typically begins with physical therapy focused on strengthening the vastus medialis obliquus (VMO) and hip stabilizers, along with patellar stabilization bracing. For patients who continue to experience recurrent subluxation episodes despite conservative management, surgical options such as MPFL reconstruction, tibial tubercle osteotomy, or trochleoplasty may be considered. Dr. Jeremy Burnham evaluates each patient’s anatomy and instability pattern to determine the most appropriate treatment approach, whether non-surgical or surgical.
First-Time vs. Recurrent Patellar Dislocation
One of the most clinically important distinctions in patellar instability is whether a patient is experiencing their first dislocation or a recurrent episode. The management approach, surgical risk assessment, and long-term prognosis differ significantly between these two groups.
Most first-time patellar dislocations in young athletes are treated non-surgically with immobilization followed by structured physical therapy. However, the recurrence rate after a first dislocation is notably high, ranging from 15% to 44% in published studies. This risk increases substantially when anatomic risk factors are present, such as trochlear dysplasia, patella alta, or an elevated tibial tubercle-trochlear groove (TTTG) distance.
Patients who experience a second or third dislocation have a significantly elevated ongoing risk and almost universally have a torn or incompetent MPFL. Progressive cartilage damage occurs with each subsequent dislocation event, which provides a strong rationale for surgical stabilization. Dr. Burnham’s 2021 editorial in Arthroscopy argued that recurrent patellar instability requires an individualized, anatomic approach, similar to the philosophy behind modern ACL reconstruction, that addresses each patient’s specific structural abnormalities (MPFL, trochlea, tibial tubercle, limb alignment) rather than applying a one-size-fits-all procedure. For patients with recurrent instability, surgical consultation is generally recommended after a second dislocation event to prevent progressive cartilage damage.
| Feature | First Dislocation | Recurrent Dislocation |
|---|---|---|
| Typical initial treatment | Non-surgical in most cases | Surgical consultation generally recommended after 2nd+ episode |
| MPFL status | Acutely torn | Chronically torn or incompetent |
| Cartilage damage | Usually mild to moderate | Progressive with each episode |
| Recurrence risk | 15-44% without surgery | High (>50%) without surgical stabilization |
| Key surgical considerations | Significant bony abnormalities or failed conservative care | MPFL reconstruction ± tibial tubercle transfer or trochleoplasty based on anatomy |
| Recommended workup | Clinical exam + MRI | Clinical exam + MRI + CT for TTTG distance and trochlear morphology |
FAQ. Frequently Asked Questions
How do you treat patella dislocation?
There are a few different ways that patella dislocations can be treated, depending on the severity of the injury. For less severe cases, the doctor may simply recommend resting and icing the knee to reduce swelling. They may also prescribe a physical therapy regimen to help strengthen the muscles around the knee, and a patellar stabilization brace to help the kneecap stay in place.
For more severe cases, or in the case of recurrent instability, surgery may be necessary to repair any damage to the ligaments or bones. After surgery, you will likely need to go through physical therapy to regain strength and flexibility in your knee.
How serious is a patella dislocation?
A patella dislocation is a serious injury. It occurs when the patella, or kneecap, pops out of place. This can happen due to a fall, a direct blow to the knee, or sudden twisting motion. Patella dislocations are most common in young people aged 15-25 years old.
Patella dislocations can be very painful and may cause the knee to swell up. You may also have trouble moving your leg or bearing weight on it. In some cases, patella dislocations can damage the surrounding ligaments, nerves, or blood vessels.
Can you walk on a dislocated patella?
A patella dislocation, also known as a dislocated kneecap, is a very painful injury. If the kneecap is dislocated, you will be unable to walk during that time. After the knee cap goes back in place (either on its own or with the help of a healthcare provider), the ability to walk is variable.
In some cases, the pain is minimal, and the knee stability is adequate to allow walking. In other cases, the pain and/or the degree of knee stability limits the ability to walk.
What is the difference between patella subluxation versus dislocation?
Patella subluxation is a partial dislocation of the patella, meaning that the patella partially pops out of place. A patella dislocation is a complete dislocation, meaning that the patella completely pops out of place.
Patellar subluxation and patellar dislocation can both cause pain, swelling, and instability in the knee joint. Patellar subluxation is often treated with physical therapy and knee braces. Patellar dislocation may require surgery to repair the ligaments around the knee joint.
If you think you may have patellar subluxation or patellar dislocation, it is important to see a doctor or orthopedic surgeon.
How bad is the pain after patellar dislocation?
The pain is typically very severe and can cause the person to stop whatever activity they are doing. It may also be accompanied by a popping or snapping sound. The knee will usually swell and look deformed. There may also be bruising around the knee.
What are the risk factors for kneecap dislocation?
There are several risk factors that increase the likelihood of patellar dislocation, including:
– previous patellar dislocation
– structural abnormalities in the knee, such as a shallow groove for the patella to sit in (trochlear dysplasia)
– loose ligaments around the knee joint
– muscle weakness or imbalances around the knee joint
– impact to the kneecap from the side
Can you walk on a dislocated kneecap?
A patella dislocation, also known as a dislocated kneecap, is a condition in which the patella (kneecap) becomes dislodged from its normal position. This can occur due to a traumatic injury, such as a fall or car accident, or due to overuse of the knee joint.
Symptoms of a patella dislocation include knee pain, swelling, and deformity. The patella may also appear to be shifted to the outside of the knee joint. In some cases, patellar dislocations may also cause nerve damage and/or bruising. The pain or instability may be so severe that you can’t walk on it. However, in some cases, especially with mild injuries or minimal subluxation, you may be able to immediately walk after injury.
How long does it take to heal a dislocated kneecap?
Recovery time for a dislocated kneecap depends on the severity of the injury and whether surgery is required. For a first-time dislocation treated without surgery, most patients can return to light activities within 4 to 6 weeks, with full return to sports typically assessed at 6 to 8 weeks. If surgery is needed (such as MPFL reconstruction), the recovery timeline is longer, generally 4 to 6 months before returning to full athletic activity. Physical therapy plays a critical role in recovery regardless of whether the dislocation is treated surgically or non-surgically.
Can a dislocated kneecap fix itself?
In many cases, a dislocated kneecap will spontaneously relocate (slide back into place) on its own, especially if the knee is gently straightened. This is called spontaneous reduction. However, even when the kneecap goes back into position on its own, the injury still requires medical evaluation. The dislocation often damages the medial patellofemoral ligament (MPFL) and may cause cartilage injuries or bone bruising that need to be assessed with X-rays and potentially an MRI. Simply because the kneecap returned to its normal position does not mean the knee is fully healed.
What does a swollen dislocated kneecap look like?
After a patellar dislocation, the knee typically swells significantly within the first few hours. The swelling is caused by bleeding inside the joint (hemarthrosis) from torn soft tissues, particularly the MPFL. The knee may appear visibly enlarged compared to the other side, with puffiness concentrated around and above the kneecap. There is often bruising along the inner (medial) side of the knee where the MPFL was torn, and sometimes bruising on the outer (lateral) side of the knee where the kneecap impacted during the dislocation. The kneecap itself may appear slightly shifted if it has not fully relocated.
What is the difference between patellar subluxation and dislocation?
Patellar subluxation is a partial displacement of the kneecap where it shifts out of its normal groove but does not completely dislocate. Patients often describe a feeling of the kneecap “slipping” or “catching” before it returns to position. A full patellar dislocation occurs when the kneecap completely displaces out of the trochlear groove, usually to the outside (lateral side) of the knee.
Both conditions involve similar underlying risk factors, including trochlear dysplasia, ligamentous laxity, and MPFL insufficiency. Subluxation episodes tend to be less traumatic than full dislocations but can still cause cartilage damage over time if left untreated. Treatment for both conditions ranges from physical therapy and bracing to surgical procedures such as MPFL reconstruction, depending on the frequency and severity of episodes.
What does a dislocated knee mean?
A dislocated knee can refer to two different injuries. When people say they have a dislocated knee or dislocated kneecap, they usually mean a patellar dislocation, which is when the kneecap (patella) slips out of its groove on the front of the knee. This is a common injury in young athletes. A true knee dislocation, by contrast, is a rare and severe injury where the tibia (shin bone) and femur (thigh bone) separate from each other at the knee joint, often tearing multiple ligaments simultaneously. Patellar dislocation is far more common than true knee dislocation and has a very different treatment course. If you are not sure which type of injury you have sustained, it is important to seek evaluation from an orthopedic specialist.
Is a dislocated kneecap the same as a dislocated knee?
Not exactly. A dislocated kneecap (patellar dislocation) refers specifically to the kneecap sliding out of its trochlear groove, usually to the outside of the knee. This is a relatively common sports injury, particularly in teenagers and young adults. A true knee dislocation refers to a far more severe injury in which the two main bones of the knee joint (femur and tibia) are completely displaced from each other, tearing multiple ligaments and sometimes injuring blood vessels or nerves. True knee dislocations are uncommon and represent orthopedic emergencies. When most people say they dislocated their knee during sports, they are describing a patellar (kneecap) dislocation.
What happens if a dislocated kneecap is left untreated?
Leaving a patellar dislocation untreated can lead to significant long-term problems. Most importantly, an untreated first dislocation leaves the medial patellofemoral ligament (MPFL) torn and the kneecap unstable, dramatically increasing the risk of repeat dislocations. With each subsequent dislocation, cartilage on the underside of the kneecap and the trochlear groove is progressively damaged, which can lead to early-onset patellofemoral arthritis. Patients who experience recurrent, untreated patellar instability often develop chronic knee pain, giving-way episodes, and activity limitations well before middle age. Early evaluation after a first dislocation is important to assess for loose bodies, cartilage injuries, and anatomic risk factors that might warrant surgical stabilization before further damage occurs.
References & Recommended Reading
- Burnham JM. Editorial Commentary: Treating Patients With Recurrent Patellar Instability With an Individualized, Anatomic Approach Is Needed: Learn From the Anterior Cruciate Ligament. Arthroscopy. 2021 May;37(5):1680-1682. doi: 10.1016/j.arthro.2021.01.018. PMID: 33896516.
- Dewan V, Webb MSL, Prakash D, Malik A, Gella S, Kipps C. Patella dislocation: an online systematic video analysis of the mechanism of injury. Knee Surg Relat Res. 2020 May 27;32(1):24. doi: 10.1186/s43019-020-00031-w. PMID: 32660635; PMCID: PMC7251696.
- Bulgheroni E, Vasso M, Losco M, Di Giacomo G, Benigni G, Bertoldi L, Schiavone Panni A. Management of the First Patellar Dislocation: A Narrative Review. Joints. 2019 Dec 31;7(3):107-114. doi: 10.1055/s-0039-3401817. PMID: 34195538; PMCID: PMC8236325.
Dr. Jeremy Burnham is fellowship-trained in the treatment of sports medicine knee injuries such as dislocation of the kneecap (Patellar dislocation). He treats patients in the Louisiana and Mississippi area including Baton Rouge, Hammond, Brusly, Walker, Denham Springs, Walker, New Roads, St. Francisville, Central, Zachary, Port Allen, Plaquemine, Gonzales, Prairieville, Natchez, Centreville, Woodville.