Patellar Dislocation and Instability
Restore Knee Stability. Regain Confidence. Return to an Active Life.
Patellar dislocation and instability occur when the kneecap (patella) moves partially or completely out of its normal position within the groove at the front of the knee.This may occur following a sports injury, sudden twisting movement, direct trauma, or because of underlying anatomical factors that predispose the kneecap to instability.
Patients may experience pain, swelling, recurrent dislocations, or a sensation that the kneecap is slipping out of place. Repeated episodes can damage the surrounding ligaments and joint cartilage, potentially affecting long-term knee function.
Treatment focuses on restoring kneecap stability, protecting the joint cartilage, and helping patients return to their everyday activities and sports with confidence.Depending on the severity of instability and underlying anatomy, treatment may involve physiotherapy, bracing, ligament reconstruction, or corrective bony procedures.
What Is Patellar Dislocation and Instability?
The patella is a small bone located at the front of the knee. It normally moves within a groove at the lower end of the thighbone (femur), called the trochlear groove, as the knee bends and straightens.
Its stability depends on the shape of the joint, surrounding muscles, ligaments, and alignment of the lower limb.
The Medial Patellofemoral Ligament (MPFL) is an important structure that helps prevent the kneecap from moving excessively towards the outer side of the knee.
When these stabilising structures are injured or the underlying anatomy predisposes the patella to abnormal movement, instability may occur.
Patellar Subluxation: The kneecap partially slips out of its normal position but does not completely dislocate.
Patellar Dislocation: The kneecap moves completely out of its normal groove, usually towards the outer side of the knee.
Recurrent Patellar Instability: Repeated episodes of dislocation, subluxation, or a persistent sensation that the kneecap may slip out of place.
Some dislocations reduce spontaneously, while others require medical assistance to restore the kneecap to its normal position.
What Causes Patellar Dislocation?
Patellar instability may develop following an injury or because of anatomical and mechanical factors that affect normal kneecap movement.
Common causes and contributing factors include:
Sports Injuries and Trauma: Sudden twisting, pivoting, awkward landings, or direct impact during sports and physical activity can cause the kneecap to dislocate.
MPFL Injury: The medial patellofemoral ligament is frequently injured during lateral patellar dislocation, reducing the soft-tissue restraint against further instability.
Trochlear Dysplasia: A shallow or abnormally shaped trochlear groove may provide insufficient bony support to keep the kneecap stable.
Patella Alta: An unusually high-riding kneecap may engage the trochlear groove later during knee bending, increasing the risk of instability.
Abnormal Patellar Alignment: Increased lateral positioning of the patellar tendon attachment, sometimes measured using the tibial tubercle trochlear groove (TT–TG) distance, may contribute to abnormal patellar tracking.
Lower Limb Malalignment: Knock-knee deformity (genu valgum) or abnormal rotation of the femur or tibia may alter the forces acting on the kneecap.
Generalised Joint Laxity: Increased ligament flexibility or hypermobility can predispose some patients to recurrent instability.
Identifying the underlying cause is essential because patellar instability is not always simply a ligament injury. Successful treatment often requires addressing the anatomical and mechanical factors responsible for the instability.
Symptoms of Patellar Dislocation and Instability
Patients may experience:
- Sudden pain at the front of the knee following an injury.
- Visible displacement of the kneecap.
- Swelling around the knee.
- A popping sensation during injury.
- Difficulty walking or bearing weight.
- A feeling that the kneecap is slipping or giving way.
- Recurrent episodes of kneecap dislocation or subluxation.
- Apprehension or fear during certain knee movements.
- Difficulty running, squatting, climbing stairs, or participating in sports.
- Persistent pain, stiffness, or reduced knee movement.
Some patients experience repeated instability without a major injury, particularly when underlying anatomical abnormalities are present. An acute dislocation requires prompt medical evaluation, even if the kneecap returns to its normal position on its own. If it remains dislocated, urgent medical attention is required.
How Is Patellar Instability Diagnosed?
A detailed clinical examination and appropriate imaging help identify the cause of instability and guide treatment.
- Clinical Examination : Your surgeon assesses kneecap movement, patellar tracking, ligament stability, knee alignment, muscle function, and any signs of generalised joint laxity.
- X-rays : Knee X-rays, including specialised views of the kneecap, help evaluate joint alignment, patellar position, trochlear shape, fractures, and associated bony abnormalities.
- MRI Scan : MRI helps identify MPFL injuries, cartilage damage, osteochondral fractures, and other soft tissue injuries. It can also help assess anatomical factors contributing to instability.
- CT Scan : In selected cases, CT imaging may be recommended for detailed assessment of bony anatomy, rotational deformity, or surgical planning.
The aim is not simply to confirm that the patella has dislocated, but to understand why it happened and assess the risk of further instability.
Can Patellar Dislocation Be Treated Without Surgery?
Yes. Many patients experiencing their first patellar dislocation can be managed without surgery, particularly when there is no significant associated cartilage or bone injury and the knee does not have major predisposing abnormalities.
Non-surgical treatment may include:
- Pain and Swelling Management: Rest from aggravating activities, ice, appropriate medication, and temporary activity modification.
- Patellar Stabilising Brace: A brace may provide comfort and support during the early recovery period.
- Physiotherapy: Targeted rehabilitation helps restore movement, improve muscle strength, and regain knee stability.
- Quadriceps and Hip Strengthening: Strengthening the muscles around the knee and hip can improve lower-limb control.
- Balance and Movement Training: Exercises help improve coordination, neuromuscular control, and confidence.
- Gradual Return to Sports: Sporting activities are resumed progressively after adequate functional recovery.
However, some patients have anatomical abnormalities, significant associated injuries, or a higher risk of recurrent dislocation that may warrant consideration of early surgical treatment. Your surgeon will evaluate your injury, anatomical risk factors, activity requirements, and risk of recurrence before recommending the most appropriate treatment.
When Is Surgery Recommended for Patellar Instability?
Surgery may be considered when the kneecap repeatedly dislocates, remains unstable despite appropriate rehabilitation, or when significant associated injuries or anatomical abnormalities are present.
Common indications include:
- Recurrent patellar dislocations.
- Persistent instability affecting daily activities or sports.
- Significant MPFL injury with recurrent instability.
- Osteochondral fractures or displaced cartilage fragments requiring treatment.
- Severe trochlear dysplasia associated with recurrent instability.
- Patella alta or abnormal patellar alignment contributing to repeated dislocations.
- Significant lower-limb malalignment or rotational deformity.
- Selected first-time dislocations with substantial risk factors or associated injuries.
Not every patient requires the same surgical procedure. The choice depends on the underlying cause of instability, joint anatomy, cartilage condition, skeletal maturity, and individual functional requirements.
Conventional vs Robotic-Assisted Partial Knee Replacement
Unicompartmental knee replacement can be performed using conventional surgical instruments or robotic-assisted technology.
- Conventional Partial Knee Replacement
Conventional surgery uses established surgical instruments and techniques to prepare the damaged joint surfaces and position the implants.
- Robotic-Assisted Partial Knee Replacement
Robotic-assisted surgery uses computer assisted planning and intraoperative guidance to help the surgeon assess knee anatomy, plan implant positioning, and execute bone preparation with greater precision.
The surgeon remains in control throughout the procedure.
Robotic technology may improve the accuracy and consistency of implant positioning. However, its ability to provide superior long-term clinical outcomes compared with well performed conventional surgery remains an area of ongoing research.
Your surgeon will discuss the suitability, advantages, and limitations of each approach based on your individual knee condition.
What Surgical Procedures Are Used to Treat Patellar Instability?
Several surgical techniques may be used individually or in combination to restore kneecap stability.
Medial Patellofemoral Ligament (MPFL) Reconstruction
MPFL reconstruction is one of the most commonly performed procedures for recurrent lateral patellar instability. The MPFL is an important ligament on the inner side of the knee that helps prevent the kneecap from dislocating outwards.
When this ligament is damaged or insufficient, it can be reconstructed using a tendon graft, commonly obtained from one of the patient’s own tendons or an appropriate donor graft.
The graft is positioned to restore the ligament’s stabilising function and help maintain normal patellar tracking. MPFL reconstruction aims to prevent recurrent dislocations while preserving natural knee movement and function.
In appropriately selected patients without significant underlying bony abnormalities, isolated MPFL reconstruction may be sufficient.
Tibial Tubercle Osteotomy (TTO)
A tibial tubercle osteotomy is a corrective procedure used in selected patients with abnormal patellar alignment or a high-riding kneecap.
The tibial tubercle, where the patellar tendon attaches to the shinbone, is carefully repositioned to improve the direction of forces acting on the kneecap.
Depending on the anatomical abnormality, the procedure may involve:
Medialisation: Moving the attachment towards the inner side of the knee to address excessive lateral positioning.
Distalisation: Moving the attachment downwards to correct significant patella alta.
Anteromedialisation: Repositioning the attachment forwards and inwards in selected cases to alter joint loading and alignment.
The repositioned bone is secured using screws until healing occurs.
Tibial tubercle osteotomy may be performed alongside MPFL reconstruction when both ligament insufficiency and significant bony abnormalities contribute to instability.
Trochleoplasty
Trochleoplasty is a specialised surgical procedure used in carefully selected patients with severe trochlear dysplasia.
In these patients, the groove in which the kneecap normally moves may be excessively shallow or abnormally shaped.
The procedure involves reshaping the trochlear groove to provide improved bony guidance and stability for the kneecap.
Trochleoplasty is generally reserved for selected skeletally mature patients with severe trochlear dysplasia and recurrent instability. It may be combined with MPFL reconstruction or other corrective procedures when indicated.
Corrective Osteotomy for Lower Limb Malalignment
Some patients develop patellar instability partly because of significant knock-knee deformity or abnormal rotational alignment of the lower limb.
In selected cases, a corrective femoral or tibial osteotomy may be required to address the underlying deformity and improve patellar tracking.
These procedures are considered when the malalignment contributes substantially to recurrent instability.
Arthroscopic Treatment of Associated Injuries
Patellar dislocations can sometimes cause cartilage damage, osteochondral fractures, or loose fragments within the knee.
Arthroscopy may be used to evaluate and treat associated joint injuries through small incisions using a camera and specialised instruments.
Depending on the findings, treatment may include removal of symptomatic loose bodies, fixation of suitable osteochondral fragments, or cartilage repair procedures.
Patellar stabilisation frequently involves ligament reconstruction or corrective bone procedures, which are not necessarily performed entirely through arthroscopy.
Your surgeon will determine whether arthroscopy, an open stabilisation procedure, or a combination of techniques is appropriate.
Expert Patellar Dislocation and Instability Treatment in Mumbai
Dr. Dhruva Utkarsh Angachekar is a fellowship trained Orthopaedic Surgeon in Mumbai with advanced international training in knee arthroscopy, sports injuries, ligament reconstruction, knee preservation, osteotomies, and deformity correction.
How Is Patellar Stabilisation Surgery Performed?
The surgical procedure varies according to the underlying cause of instability and the treatment required.
- Preoperative Evaluation : Your surgeon evaluates the history of dislocations, knee stability, anatomical alignment, ligament condition, cartilage damage, and relevant imaging findings.
- Surgical Planning : A personalised surgical plan is developed to address the underlying cause of instability. This may involve ligament reconstruction, correction of bony alignment, or a combination of procedures.
- Assessment and Treatment of Associated Injuries : Where necessary, arthroscopy is performed to evaluate the joint and treat cartilage injuries or loose fragments.
- Ligament Reconstruction or Corrective Procedure : The MPFL is reconstructed when indicated. Additional procedures, such as tibial tubercle osteotomy or trochleoplasty, may be performed if significant anatomical abnormalities require correction.
- Assessment of Patellar Tracking and Stability : The surgeon evaluates kneecap movement, alignment, and stability throughout the appropriate range of knee motion.
- Postoperative Care : Following surgery, patients receive appropriate pain management, wound care, bracing or walking aids when necessary, and a structured rehabilitation programme.
What Happens After Patellar Stabilisation Surgery?
Recovery depends on the procedure performed, any associated cartilage or bony reconstruction, and individual rehabilitation progress.
Following an isolated MPFL reconstruction, many patients begin walking with assistance shortly after surgery, subject to the surgeon’s weight-bearing and bracing instructions.
When additional procedures such as tibial tubercle osteotomy or cartilage repair are performed, weight-bearing, knee movement, and activity progression may be restricted for a longer period to protect healing tissues and bone.
Rehabilitation focuses on restoring knee movement, rebuilding quadriceps strength, improving stability, and gradually returning to daily activities and sports.
Rehabilitation After Patellar Stabilisation Surgery
A structured postoperative rehabilitation programme is essential for restoring knee strength, movement, and stability while protecting the reconstructed ligament and any associated bony procedures.
- Phase 1: Early Recovery (Weeks 0–2) The initial focus is on controlling pain and swelling, protecting the surgical reconstruction, and beginning appropriate knee movement.
Patients may use a brace and crutches according to their surgeon’s instructions. Gentle exercises help activate the quadriceps and maintain muscle function. - Phase 2: Restoring Movement (Weeks 2–6) Rehabilitation progresses towards improving knee bending and straightening, quadriceps activation, and walking ability.
Weight-bearing and brace use are adjusted according to the surgical procedure and recovery. Patients undergoing additional bony procedures may require more prolonged restrictions. - Phase 3: Strengthening and Functional Recovery (Weeks 6–12) As movement and stability improve, rehabilitation focuses on progressive muscle strengthening, balance, walking mechanics, and functional exercises.
Patients gradually resume routine daily activities and may begin suitable low-impact exercises under supervision. - Phase 4: Advanced Rehabilitation (Months 3–6) The focus shifts towards improving strength, endurance, neuromuscular control, and confidence during more demanding activities.
Selected patients may begin jogging, controlled jumping, agility exercises, and progressive sports-specific training when appropriate functional criteria are achieved. - Phase 5: Return to Sports (Months 6–12 and Beyond) Return to sport is based on adequate healing, muscle strength, knee stability, balance, functional testing, and psychological readiness.
Many patients may begin progressing towards sports participation after approximately six months, while competitive or high-demand sports may require 9–12 months or longer, depending on the procedure and individual recovery.
Patients undergoing combined ligament reconstruction and bony procedures may require a longer rehabilitation period.
Your surgeon and physiotherapy team will guide you through a personalised rehabilitation programme, with progression based on clinical recovery rather than time alone.
“These milestones are general guidelines and may vary considerably depending on the procedure performed.”
What Are the Benefits of Patellar Stabilisation Surgery?
For appropriately selected patients, surgical treatment may provide:
- Reduced episodes of patellar dislocation.
- Improved kneecap stability and tracking.
- Greater confidence during walking and physical activity.
- Reduced apprehension during knee movement.
- Improved ability to participate in daily activities and sports.
- Treatment of associated cartilage or osteochondral injuries.
- Correction of relevant anatomical abnormalities.
- Potential reduction in further instability related joint injury.
The objective is to restore stable, functional kneecap movement while preserving the natural knee joint whenever possible. Results vary between patients, and surgery does not guarantee complete pain relief or eliminate the possibility of future instability.
Are There Any Risks Associated With Patellar Stabilisation Surgery?
As with any orthopaedic procedure, patellar stabilisation surgery carries certain risks.
Potential complications include infection, blood clots, persistent pain or swelling, knee stiffness, reduced movement, recurrent instability, and complications related to graft fixation or healing.
MPFL reconstruction may occasionally result in graft failure or excessive tightness, which can affect kneecap movement.
Procedures involving bone correction carry additional risks, including delayed bone healing, nonunion, hardware irritation, or the need for further surgery.
A detailed preoperative assessment and carefully planned rehabilitation help minimise complications. Your surgeon will discuss the potential benefits, limitations, and risks of the proposed procedure before surgery.
Is Patellar Stabilisation Surgery Right for Everyone?
Not every patient with patellar instability requires surgery.
The decision depends on:
- Whether the dislocation is a first-time or recurrent episode.
- The severity of ligament damage.
- Associated cartilage or osteochondral injuries.
- Trochlear morphology and patellar height.
- Lower-limb alignment and rotational abnormalities.
- Age and skeletal maturity.
- Response to physiotherapy and non-surgical treatment.
- Activity requirements and sporting goals.
- Individual expectations and functional limitations.
The most appropriate treatment is determined by the underlying cause of instability rather than the number of dislocations alone.
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Frequently Asked Questions
Not necessarily. Many patients recover after a first-time patellar dislocation without experiencing further episodes.
However, the risk of recurrence is higher in some patients, particularly younger individuals and those with trochlear dysplasia, patella alta, generalised joint laxity, or other anatomical risk factors.
Your surgeon will assess these factors and discuss your individual risk of recurrence.
No. Many first-time patellar dislocations can be treated without surgery.
Physiotherapy, temporary bracing, and structured rehabilitation are often effective. Surgery may be considered for recurrent instability, significant cartilage or bone injuries, or selected high-risk cases.
MPFL reconstruction involves replacing the damaged medial patellofemoral ligament with a tendon graft to help stabilise the kneecap.
It is commonly recommended for recurrent patellar instability when ligament insufficiency is a major contributing factor.
Your surgeon will determine whether isolated MPFL reconstruction is sufficient or whether additional corrective procedures are required.
MPFL reconstruction is generally performed using small open incisions or minimally invasive surgical techniques to position and secure the ligament graft.
Arthroscopy may be performed alongside the reconstruction to evaluate and treat associated cartilage injuries or loose bodies.
Yes. Some patients have underlying anatomical factors such as trochlear dysplasia, patella alta, abnormal limb alignment, or joint hypermobility that predispose them to instability.
In these cases, the kneecap may dislocate during relatively minor movements or routine activities.
Yes. Patellar instability is particularly common among adolescents and young athletes.
Treatment depends on the severity of instability, associated injuries, anatomical risk factors, and whether the growth plates are still open.
Surgical techniques may need to be modified in patients who have not completed skeletal growth.
Many patients gradually return to routine daily activities over the first several weeks, with continued improvements in strength and knee function over subsequent months.
Return to sporting activities commonly requires six months or longer, while competitive sports may require additional rehabilitation.
Recovery may take longer when procedures such as tibial tubercle osteotomy or cartilage repair are performed.
Many patients return to sporting activities after successful rehabilitation.
However, returning to competitive sports requires adequate knee strength, stability, balance, movement control, and confidence.
Your surgeon will assess your progress and guide a gradual return to sports based on functional recovery and the demands of your activity.
Yes. Repeated dislocations may cause cartilage injuries involving the kneecap or trochlear groove, sometimes resulting in loose osteochondral fragments within the joint.
These injuries may contribute to persistent pain and increase the risk of longer-term joint problems.
Early evaluation helps identify associated injuries and determine whether treatment is required.
Physiotherapy plays an important role in strengthening the quadriceps and hip muscles, improving movement control, and restoring confidence.
It may be sufficient for many first-time dislocations. However, patients with recurrent instability or significant anatomical abnormalities may require surgical treatment despite appropriate rehabilitation.
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