Dislocated Kneecap: Symptoms, Treatment & Recovery

What Is a Dislocated Kneecap?

A dislocated kneecap (patellar dislocation) occurs when the patella, the small bone at the front of the knee, slides out of the trochlear groove where it normally sits. The kneecap almost always displaces laterally (to the outside of the knee). This injury commonly results from a direct blow to the knee or a sudden twisting motion during sports activities.

The kneecap, or patella, is a sesamoid bone embedded within the quadriceps tendon that plays a crucial role in knee function. It serves as a fulcrum that increases the mechanical advantage of the quadriceps muscles, allowing for more powerful leg extension. The patella glides within a groove called the trochlea on the front of the thighbone (femur). When this tracking mechanism is disrupted, a dislocation can occur.

Patellar dislocation is one of the most common knee injuries in young people, with an annual incidence of approximately 5.8 to 7 cases per 100,000 people. The injury occurs most frequently in adolescents aged 10-17 years, particularly those who participate in sports involving cutting, pivoting, or jumping movements such as basketball, soccer, volleyball, and gymnastics. Female athletes have a slightly higher incidence than males.

Understanding the anatomy of the knee helps explain why dislocations occur and why certain individuals are more susceptible. The medial patellofemoral ligament (MPFL) is the primary soft tissue restraint preventing lateral patellar displacement. When the kneecap dislocates, this ligament is almost always torn or stretched, which is why proper healing and rehabilitation are so important for preventing future episodes.

It's important to distinguish between a true patellar dislocation and patellar subluxation. In a complete dislocation, the kneecap moves entirely out of its groove and may remain displaced until manually reduced. In subluxation, the kneecap partially slips out of place but returns to its normal position without intervention. Both conditions indicate underlying instability and require appropriate management.

Who Is Most at Risk?

Several factors increase the risk of patellar dislocation. Adolescents and young adults are most commonly affected, with the highest incidence occurring between ages 10-17 years. Athletes participating in sports that involve sudden direction changes, jumping, or pivoting are particularly vulnerable. Additionally, certain anatomical variations such as a shallow trochlear groove (trochlear dysplasia), high-riding kneecap (patella alta), increased Q-angle, or generalized joint hypermobility can predispose individuals to patellar instability.

What Causes the Kneecap to Dislocate?

The mechanism of injury typically involves one of two scenarios. The first is a direct blow to the medial (inner) side of the kneecap, forcefully pushing it laterally out of the groove. The second, and more common, mechanism is a non-contact injury where the knee twists while the foot is planted on the ground. This often occurs when landing from a jump or making a sudden cutting movement. In this scenario, the quadriceps muscle contracts forcefully while the knee is slightly bent and rotated inward, creating forces that push the kneecap outward.

What Are the Symptoms of a Dislocated Kneecap?

The main symptoms of a dislocated kneecap include sudden, severe pain at the front of the knee, visible displacement of the kneecap to the outer side of the knee, immediate swelling, inability to straighten or bend the leg, and difficulty bearing weight. Many patients report feeling or seeing the kneecap "pop out" of place.

When a kneecap dislocates, the symptoms are typically immediate and dramatic. The most prominent symptom is severe pain at the front and side of the knee. This pain is often described as sharp, intense, and debilitating, though interestingly, patients who have experienced previous dislocations often report less severe pain with subsequent episodes. The body may develop some tolerance or the tissue damage may be less extensive in recurrent cases.

Visual changes to the knee are often apparent. When the kneecap remains dislocated, you may be able to see it sitting abnormally on the outer side of the knee, creating an obvious deformity. The knee joint typically swells rapidly due to bleeding from torn soft tissues and accumulation of joint fluid (effusion). This swelling can be substantial and may develop within minutes to hours of the injury.

Functional impairment is significant following a patellar dislocation. Most patients are unable to straighten their leg completely, and bending the knee may also be limited or impossible. The leg may feel unstable or "give way" when attempting to stand. Walking is usually not possible without assistance, and bearing weight on the affected leg causes increased pain.

In many cases, the kneecap will spontaneously relocate (return to its normal position) when the leg is straightened. This often happens naturally as the person extends their leg or receives first aid. When spontaneous relocation occurs, the patient may feel or hear a "pop" as the patella returns to its groove. However, even after relocation, significant pain, swelling, and functional limitation persist due to the soft tissue damage that occurred during the dislocation.

Common Symptoms Include:

• Severe knee pain: Immediate, intense pain at the front and outer side of the knee
• Visible deformity: The kneecap may appear displaced to the outer side of the knee
• Rapid swelling: Significant swelling develops quickly due to bleeding and fluid accumulation
• Inability to move the leg: Difficulty or inability to straighten, bend, or bear weight on the leg
• Sensation of instability: Feeling that the knee might "give way" or is unstable
• Locked knee: The knee may become stuck in a bent position if the kneecap remains out of place
• Tenderness: Pain when touching the inner side of the kneecap where the MPFL attaches

Signs That the Kneecap Has Relocated

If the kneecap returns to its normal position spontaneously, you may notice a sudden decrease in the sharp, severe pain, though a dull ache and tenderness will persist. The visible deformity will no longer be present, though the knee will still be swollen and painful. You may have felt or heard a "pop" or "click" as the patella moved back into place. Despite relocation, medical evaluation is still essential to assess for associated injuries and initiate appropriate treatment.

When Should You Seek Medical Care?

Seek immediate emergency medical care if the knee is locked in a bent position and cannot straighten, if there is severe swelling that develops rapidly, or if there is intense pain regardless of whether the leg is still or moving. If the kneecap appears obviously displaced, do not attempt to force it back into place yourself.

Any suspected patellar dislocation warrants medical evaluation, even if the kneecap appears to have returned to its normal position. The injury damages soft tissues including the medial patellofemoral ligament (MPFL), and proper assessment and treatment are necessary to ensure optimal healing and prevent future problems. Additionally, associated injuries such as osteochondral fractures (damage to cartilage and underlying bone) occur in 20-40% of cases and require identification.

Emergency care is particularly important in certain situations. If the kneecap remains dislocated and the leg is locked in a bent position, professional medical intervention is needed to safely relocate the patella. This procedure, called closed reduction, should be performed by trained medical personnel who can provide appropriate pain management and ensure the maneuver is done safely.

Severe swelling that develops rapidly after the injury indicates significant bleeding within the joint (hemarthrosis) and warrants urgent evaluation. Similarly, if the pain is extreme and does not improve with rest, elevation, and over-the-counter pain medication, prompt medical attention is advisable. Any signs of circulatory compromise such as numbness, tingling, or color changes in the foot or lower leg require immediate emergency care.

What to Expect at the Emergency Department

Medical professionals will first assess whether the kneecap is still dislocated and, if so, perform a closed reduction procedure to return it to its normal position. Pain medication and sometimes sedation are provided before this procedure to ensure patient comfort. Once the patella is in place, X-rays are typically obtained to rule out fractures and assess the bony anatomy of the knee. In some cases, an MRI may be ordered to evaluate soft tissue injuries, particularly damage to the MPFL and any cartilage injuries.

How Is a Dislocated Kneecap Treated?

Treatment for a first-time patellar dislocation typically involves closed reduction (if the kneecap hasn't spontaneously relocated), immobilization with a knee brace for 2-4 weeks, pain management, and physical therapy to restore strength and stability. Surgery is generally reserved for recurrent dislocations or cases with significant associated injuries such as osteochondral fractures.

The approach to treating a dislocated kneecap depends on several factors, including whether this is a first-time or recurrent dislocation, the presence of associated injuries, and the patient's activity level and goals. The primary objectives of treatment are to restore normal kneecap positioning, allow damaged tissues to heal, prevent recurrence, and return the patient to their desired level of activity.

For first-time dislocations, conservative (non-surgical) treatment is generally the recommended initial approach. After the kneecap is reduced (either spontaneously or by medical professionals), the knee is typically immobilized in a brace or orthosis. The type and duration of immobilization vary, but most protocols involve wearing a hinged knee brace that limits movement for approximately 2-4 weeks. This allows the torn MPFL and other damaged tissues to begin healing while preventing re-dislocation.

Pain management is an important component of treatment. Over-the-counter pain relievers such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen can help manage pain and reduce swelling. Ice application for 15-20 minutes several times daily during the first few days helps control swelling. Elevation of the leg above heart level when resting also aids in reducing swelling.

Physical therapy is a cornerstone of treatment and is essential for both recovery and prevention of recurrence. A structured rehabilitation program typically begins once the initial acute phase has passed, usually within the first week or two after injury. The goals of physical therapy include restoring range of motion, strengthening the quadriceps muscles (particularly the vastus medialis obliquus or VMO), improving hip strength, and retraining proper movement patterns.

Immediate First Aid

Before reaching medical care, certain first aid measures can help manage a dislocated kneecap. Help the injured person lie down in a comfortable position and keep them calm. Do not attempt to force the kneecap back into place, as this can cause additional damage. Support the leg in a comfortable position using pillows or cushions. Applying ice wrapped in a cloth can help reduce swelling and pain. Avoid putting weight on the affected leg. If possible, elevate the leg to reduce swelling while waiting for medical assistance.

Bracing and Support

A knee brace or orthosis is typically worn for several weeks following a patellar dislocation. These devices range from rigid braces that completely immobilize the knee to hinged braces that allow controlled movement. The purpose is to protect the healing tissues and prevent re-dislocation while gradually allowing the knee to regain mobility. Crutches are often necessary during the initial period, particularly if weight-bearing causes significant pain or instability.

When Is Surgery Needed?

Surgery is typically considered in the following situations: recurrent patellar dislocations (two or more episodes) despite appropriate conservative treatment, significant osteochondral fractures or loose bodies within the joint, high-risk anatomical factors for recurrence (such as severe trochlear dysplasia or patella alta), and first-time dislocations in high-demand athletes who require a rapid return to sport with minimal recurrence risk.

The most common surgical procedure for recurrent patellar instability is medial patellofemoral ligament (MPFL) reconstruction. This involves creating a new MPFL using a graft (often from the patient's own hamstring tendon) to restore the primary stabilizer of the patella. Success rates for MPFL reconstruction are excellent, with 85-95% of patients achieving stable knees without recurrent dislocation. Additional procedures such as tibial tubercle transfer or trochleoplasty may be performed in cases with significant underlying anatomical abnormalities.

What Can You Do Yourself?

Immediately after a kneecap dislocation, lie down and elevate the leg above heart level. Apply ice wrapped in a cloth for 15-20 minutes to reduce swelling. Do not try to force the kneecap back into place. Avoid bearing weight on the leg and seek medical care. Over-the-counter pain relievers can help manage discomfort.

In the immediate aftermath of a patellar dislocation, proper first aid can help minimize pain and swelling while awaiting medical care. The most important initial step is to keep still and avoid moving the injured leg. Attempting to walk or straighten the leg forcefully can cause additional damage or increase pain. If possible, have someone help you get to a lying or sitting position where you can rest comfortably.

Elevation is one of the most effective measures for reducing swelling. Position the leg so that the knee is above the level of your heart. This can be accomplished by lying down and placing pillows under the lower leg and ankle. Elevation helps fluid drain away from the injured area and reduces the pressure within the joint.

Cold therapy is beneficial for reducing swelling and numbing pain. Apply an ice pack or a bag of frozen vegetables wrapped in a thin cloth to the knee for 15-20 minutes at a time. Avoid applying ice directly to the skin, as this can cause cold burns. Ice can be applied every 2-3 hours during the first 48-72 hours after injury.

Pain management is important for comfort. Over-the-counter pain relievers such as acetaminophen (paracetamol) or ibuprofen can help reduce pain and, in the case of NSAIDs like ibuprofen, also help control inflammation. Follow the dosing instructions on the package and be aware of any contraindications based on your medical history.

Preventing Future Dislocations

Once the acute phase has passed and healing has progressed, taking steps to prevent future dislocations becomes paramount. Strengthening the muscles around the knee, particularly the quadriceps and hip muscles, is the most effective way to reduce recurrence risk. The vastus medialis obliquus (VMO), the innermost portion of the quadriceps muscle, plays a critical role in stabilizing the patella and preventing it from shifting laterally.

Key exercises for preventing recurrent patellar dislocation include straight leg raises, quad sets (isometric quadriceps contractions), mini squats, step-ups, and leg presses. Hip strengthening exercises targeting the hip abductors and external rotators are also important, as hip weakness can contribute to altered knee mechanics and patellar tracking problems. A physical therapist can design a personalized exercise program based on your specific needs and fitness level.

Proprioceptive training, which involves exercises that improve joint position sense and neuromuscular control, is another important component of prevention. Balance exercises, single-leg stance activities, and sport-specific drills help retrain the nervous system to better protect the knee during dynamic activities.

How Long Does Recovery Take?

Recovery from a first patellar dislocation typically takes 6-12 weeks for initial healing, with full return to sports usually occurring at 3-6 months. The timeline varies based on the severity of tissue damage, whether surgery was required, patient age, and commitment to rehabilitation exercises.

The recovery timeline following a patellar dislocation varies considerably depending on individual factors. However, understanding the general phases of recovery can help set realistic expectations and guide the rehabilitation process. Most patients can expect their recovery to progress through several distinct phases, each with specific goals and activities.

During the first one to two weeks (acute phase), the focus is on protecting the injured structures, managing pain and swelling, and initiating gentle range of motion exercises within pain-free limits. Most patients wear a knee brace and use crutches during this phase. Ice, elevation, and pain medication are used as needed to manage symptoms.

From weeks two to six (early rehabilitation), patients gradually increase their range of motion and begin more active strengthening exercises. The brace may be worn less frequently, and many patients can discontinue crutches as pain allows. Physical therapy typically becomes more intensive during this phase, with a focus on quadriceps strengthening, particularly the VMO.

Between weeks six and twelve (late rehabilitation), most patients achieve full or near-full range of motion and can walk normally without assistive devices. Strengthening exercises progress to include more functional activities such as squats, lunges, and stair climbing. Balance and proprioceptive training become important components of rehabilitation.

Return to full activity, including sports, typically occurs between three and six months after injury, depending on the demands of the activity and the patient's recovery progress. For athletes, sport-specific training is introduced gradually, and return to competition is guided by objective criteria such as strength testing and functional performance measures.

Factors Affecting Recovery Time

Several factors influence how quickly and completely someone recovers from a patellar dislocation. The extent of soft tissue damage plays a significant role; more severe injuries with larger MPFL tears or associated cartilage damage may take longer to heal. Whether surgery was required also affects the timeline, with surgical patients generally having longer recovery periods but potentially better long-term stability.

Age can influence recovery, with younger patients often healing faster but also having higher recurrence rates. Commitment to rehabilitation exercises is crucial; patients who consistently perform their prescribed exercises and attend physical therapy sessions typically achieve better outcomes than those who are less compliant. Overall physical fitness and health status also play roles in recovery speed.

What Are the Possible Complications?

The main complications of patellar dislocation include recurrent instability (15-44% redislocation rate), patellofemoral osteoarthritis in the long term, osteochondral fractures (20-40% of cases), and persistent pain or knee stiffness. Younger patients and those with anatomical risk factors have higher recurrence rates.

While most people recover well from a patellar dislocation, certain complications can occur that may affect long-term knee health and function. Understanding these potential complications helps patients make informed decisions about treatment and underscores the importance of proper rehabilitation.

Recurrent patellar instability is the most common complication following a first dislocation. Studies report recurrence rates ranging from 15% to 44%, with younger patients and those with certain anatomical risk factors at higher risk. Each subsequent dislocation can cause additional damage to the joint and may increase the likelihood of developing osteoarthritis over time. For patients with multiple dislocations, surgical stabilization is often recommended to prevent further episodes and protect the joint.

Osteochondral injury, which involves damage to the cartilage and underlying bone surface, occurs in 20-40% of patellar dislocations. When the kneecap dislocates and then relocates, the articular surfaces can be damaged as they impact against each other. Osteochondral fractures may produce loose bodies within the joint that can cause mechanical symptoms such as catching, locking, or giving way. These injuries may require surgical treatment if they are large or if loose fragments are present in the joint.

Long-term, patients who have experienced patellar dislocation are at increased risk of developing patellofemoral osteoarthritis, a degenerative condition affecting the cartilage between the kneecap and thighbone. This risk is higher in patients with recurrent dislocations or those who sustained osteochondral injuries. Symptoms of patellofemoral arthritis include pain with activities such as squatting, stair climbing, or prolonged sitting, as well as crepitus (grinding sensation) in the knee.

Other Potential Complications

Persistent knee pain or stiffness can occur following patellar dislocation, even after the acute injury has healed. This may result from scarring, muscle weakness, altered movement patterns, or early arthritic changes. Comprehensive rehabilitation and, if necessary, additional treatments can help address these issues.

Muscle weakness, particularly of the quadriceps, is common after patellar dislocation and can persist if not addressed through targeted strengthening exercises. Quadriceps weakness not only affects knee function but also increases the risk of re-injury. Physical therapy focusing on muscle strengthening is essential for complete recovery.