Were You Told You Need a Simple Ligament Repair for Your Dislocating Kneecap? That May Only Be Part of the Solution.
Patellar instability — a kneecap that dislocates, subluxates, or gives way — is one of the most complex decisions in knee surgery. The simplest operation to perform is an MPFL reconstruction: rebuilding the medial patellofemoral ligament that tears when the kneecap dislocates. Most sports medicine surgeons can perform this procedure, and when performed on the right patient, it works well.
The problem is that an MPFL reconstruction performed on the wrong patient — one whose instability is driven by underlying anatomical risk factors that have not been addressed — will fail. The kneecap will dislocate again. And each dislocation causes more cartilage damage, more bone loss, and a harder problem to solve the next time.
Patellar instability is not a single diagnosis with a single solution. It is the end result of a combination of anatomical factors — some or all of which must be identified and addressed for the treatment to succeed. The surgeon who performs an MPFL reconstruction on every dislocating kneecap without evaluating the underlying anatomy is making a significant and potentially irreversible error.
Dr. Raffy Mirzayan has spent 25 years treating patellar instability at every level of complexity — from first-time dislocators who need nothing more than reassurance and rehabilitation, to patients with end-stage patellofemoral cartilage destruction who need his invented BioPFJ™ procedure to restore the joint biologically. Every treatment plan he designs begins with a thorough evaluation of every anatomical risk factor — and the surgery, when indicated, addresses all of them.
Call (310) 746-5918 to schedule a consultation. Virtual consultations are available for patients traveling from out of state.
Why Kneecaps Dislocate: The Anatomy of Instability
The patella — the kneecap — sits in a groove at the end of the femur called the trochlea. As the knee bends and straightens, the kneecap glides up and down within this groove, guided by a combination of bony architecture, soft tissue restraints, and the alignment of the entire lower extremity. When any one of these factors is abnormal, the kneecap can slip out of its groove — partially, called subluxation, or completely, called dislocation.
Understanding why a specific patient's kneecap dislocates requires evaluating every contributing factor. Dr. Mirzayan considers all of the following in every patellar instability evaluation:
Trochlear dysplasia — a shallow, flat, or convex trochlear groove that fails to capture the kneecap and guide it through its normal path. This is one of the most important risk factors for recurrent instability and one of the most commonly under-recognized. A kneecap cannot stay in a groove that is not deep enough to hold it.
Patella alta — an abnormally high kneecap position that delays engagement of the patella into the trochlear groove until late in the range of motion, leaving it unsupported and vulnerable to dislocation during the early part of knee flexion.
TTTG distance — the lateral offset of the tibial tubercle relative to the trochlear groove. An elevated TTTG indicates that the pull of the quadriceps muscle is directed too far laterally, creating a lateral force on the kneecap that predisposes it to dislocation. This is measured on MRI or CT and guides the decision about whether a tibial tubercle osteotomy is needed.
Valgus alignment — excessive knock-knee deformity that increases the lateral pull on the patella and amplifies the destabilizing forces on the patellofemoral joint.
Ligamentous laxity — generalized joint hypermobility that reduces the passive restraint on patellar motion and increases the risk of dislocation.
Age and sex — young female patients with open growth plates represent the highest-risk group for recurrent instability, and their treatment must account for skeletal immaturity.
Cartilage damage — every dislocation impacts the medial facet of the patella against the lateral femoral condyle, chipping away cartilage with each event. The degree of cartilage damage at the time of evaluation determines which procedures are appropriate and, in advanced cases, whether biological joint reconstruction is needed.
No single imaging study captures all of these factors. No algorithm replaces the judgment of a surgeon who has evaluated thousands of unstable kneecaps and understands how these variables interact.
First-Time Dislocators: When to Treat and When to Wait
Not every first-time patellar dislocation requires surgery — and Dr. Mirzayan does not operate on the majority of patients who present after a first dislocation.
Approximately one in three patients who dislocate their kneecap for the first time will never dislocate again. With appropriate conservative management — bracing, physical therapy focused on quadriceps and hip strengthening, and activity modification — many first-time dislocators recover fully without surgical intervention.
The exception is the presence of a loose body — a fragment of bone or cartilage that has been knocked off the medial patella during the dislocation and is floating free inside the joint. Loose bodies cause mechanical symptoms — catching, locking, and ongoing cartilage damage — and require arthroscopic removal regardless of whether it is a first dislocation.
For all other first-time dislocators without loose bodies, Dr. Mirzayan recommends a structured rehabilitation program before any surgical decision is made. If the patient dislocates again, the anatomy is evaluated in full and a comprehensive surgical plan is designed to address every contributing factor.
The Surgical Options: A Comprehensive Spectrum
When surgery is indicated for patellar instability — whether after a first dislocation with compelling risk factors, after recurrent dislocations, or in the setting of significant cartilage damage — Dr. Mirzayan offers the full spectrum of procedures required to address the underlying anatomy. The right combination of procedures is determined individually for each patient.
MPFL Reconstruction
The medial patellofemoral ligament is the primary soft tissue restraint that prevents lateral patellar dislocation. It tears in virtually every patellar dislocation. MPFL reconstruction — rebuilding this ligament using a tendon graft — is the foundational procedure for patellar instability surgery and is appropriate as a standalone procedure when the underlying bony anatomy is normal or near-normal. When anatomy is abnormal, MPFL reconstruction must be combined with procedures that address the bony risk factors — or it will fail.
Tibial Tubercle Osteotomy
When the TTTG distance is elevated — indicating that the tibial tubercle is positioned too far laterally — a tibial tubercle osteotomy mediates the bony attachment of the patellar tendon, redirecting the pull of the quadriceps to reduce the lateral force on the kneecap. This procedure is frequently combined with MPFL reconstruction in patients with elevated TTTG measurements. Dr. Mirzayan also performs tibial tubercle distalization — moving the tubercle distally as well as medially — in patients with patella alta, lowering the kneecap position to improve trochlear engagement.
Distal Femoral Osteotomy
In patients with significant valgus alignment — a knock-knee deformity that creates an abnormally high lateral force on the patella — a distal femoral osteotomy corrects the mechanical axis of the lower extremity and reduces the destabilizing valgus force on the patellofemoral joint. This procedure is required in a subset of patients with patellar instability and significant valgus malalignment, and it must be addressed for any soft tissue or tubercle procedure to succeed reliably.
BioPFJ™ — For End-Stage Patellofemoral Cartilage Destruction
For patients with recurrent patellar instability who have sustained significant cartilage damage to both the kneecap and the trochlear groove — particularly those with trochlear dysplasia — Dr. Mirzayan's invented BioPFJ™ procedure addresses both the instability and the cartilage destruction simultaneously.
BioPFJ™ is a complete biological reconstruction of the patellofemoral joint using fresh donor tissue from a single matched donor — replacing both the patellar and trochlear cartilage surfaces with living human cartilage and, in patients with trochlear dysplasia, correcting the abnormal groove geometry at the same time. It is the only procedure that addresses the cartilage loss and the anatomical dysplasia together, in one operation, without metal or plastic implants.
Dr. Mirzayan has performed BioPFJ™ in approximately 75 patients — more than any other surgeon in the world — with 100% graft integration, no revisions, no re-dislocations, and dramatic improvements across all functional outcome measures. His outcomes study was published in the peer-reviewed journal Cartilage: Bipolar Osteochondral Allograft Transplantation of the Patella and Trochlea — Cartilage (2018)
The Most Important Principle: Treating All the Risk Factors, Not Just the Most Obvious One
This is the central message of this page — and the most important thing a patient, parent, or referring physician needs to understand before making a surgical decision about patellar instability.
An MPFL reconstruction is not wrong. It is an excellent procedure — when performed on a patient whose instability is driven primarily by ligamentous laxity and whose bony anatomy is normal. In that patient, MPFL reconstruction alone will succeed.
But in a patient with trochlear dysplasia, patella alta, and an elevated TTTG — performing only an MPFL reconstruction is like repairing a door lock without fixing the door frame. The lock will hold for a while. But the underlying structural problem will eventually overcome it.
Every failed patellar instability surgery that comes to Dr. Mirzayan for revision has the same story: an MPFL reconstruction performed without addressing the underlying anatomical risk factors. Each of those patients dislocated again. Each of those revisions is more complex, more expensive, and more morbid than the index procedure would have been if it had been designed correctly from the start.
Getting the treatment right the first time — by evaluating every risk factor and addressing every one that is present — is not just better surgery. It is the only surgery worth doing.
What to Expect: Evaluation and Treatment
Every patellar instability evaluation begins with a detailed history and physical examination. Dr. Mirzayan assesses alignment, ligamentous laxity, patellar mobility, apprehension, and the presence of crepitus or effusion. Imaging includes standard X-rays with specific patellar views, MRI for assessment of cartilage, ligament integrity, and TTTG distance, and CT scanning when precise measurement of torsional alignment or trochlear morphology is required.
Surgery, when indicated, is planned comprehensively based on the complete anatomical picture. Recovery timelines vary depending on the procedures performed — MPFL reconstruction alone has a faster recovery than combined osteotomy procedures — and Dr. Mirzayan will give you a personalized timeline based on your specific case. Return to sport typically ranges from 4 to 6 months for isolated soft tissue procedures to 9 to 12 months for combined osteotomy and reconstruction cases.
Coming from Las Vegas, Phoenix, or Out of State?
Patellar instability is a condition where the breadth of your surgeon's anatomical knowledge and surgical repertoire matters enormously. A surgeon who offers only MPFL reconstruction will perform MPFL reconstruction — regardless of whether it addresses your underlying anatomy. A surgeon who can offer MPFL reconstruction, tibial tubercle osteotomy, tibial tubercle distalization, distal femoral osteotomy, and BioPFJ™ will design the treatment around your specific anatomy.
Dr. Mirzayan regularly treats patients from Las Vegas, Henderson, Phoenix, Scottsdale, and across the country. If you carry a commercial insurance plan — Blue Cross Blue Shield PPO, Aetna, Cigna, United Healthcare, or a self-funded employer plan — you likely have out-of-network benefits that cover a substantial portion of the cost of surgery. His office will verify your coverage before you commit to anything.
Virtual consultations are available. You can submit your MRI and CT imaging in advance, meet Dr. Mirzayan on video, and get a comprehensive assessment of your instability and all of its contributing factors before committing to travel or time away from sport.
Call (310) 746-5918 or contact us online to schedule your consultation.
Frequently Asked Questions
Do I need surgery after my first kneecap dislocation?
In most cases, no. Approximately one in three patients who dislocate their kneecap for the first time will never dislocate again with appropriate conservative management — bracing, physical therapy, and activity modification. Dr. Mirzayan recommends non-operative treatment for the majority of first-time dislocators. The exception is the presence of a loose body — a fragment of bone or cartilage knocked free during the dislocation — which requires arthroscopic removal regardless of whether it is a first event.
Why do some MPFL reconstructions fail?
Because MPFL reconstruction addresses only one component of patellar instability — the torn medial ligament. When instability is driven by trochlear dysplasia, patella alta, an elevated TTTG distance, or valgus malalignment, rebuilding the MPFL alone does not correct the underlying anatomical forces that caused the dislocation. The kneecap will eventually overcome the reconstructed ligament and dislocate again. Successful surgery requires identifying and addressing every contributing anatomical factor — not just the most visible one.
What is trochlear dysplasia and why does it matter?
Trochlear dysplasia is an abnormally shallow, flat, or convex trochlear groove — the channel in the femur where the kneecap is supposed to glide. A dysplastic trochlea fails to capture and guide the kneecap, dramatically increasing the risk of dislocation. It is one of the most important risk factors for recurrent instability and must be factored into surgical planning. In patients with trochlear dysplasia and significant cartilage damage, Dr. Mirzayan's BioPFJ™ procedure addresses both problems simultaneously — correcting the groove geometry and restoring the cartilage surface with living donor tissue.
What is a tibial tubercle osteotomy and when is it needed?
A tibial tubercle osteotomy repositions the bony attachment of the patellar tendon — moving it medially to reduce the lateral pull on the kneecap, and in some cases distally to lower an abnormally high kneecap position. It is indicated when the TTTG distance is elevated above threshold values on MRI or CT, or when patella alta is present. It is frequently performed in combination with MPFL reconstruction and is essential for a durable result in patients with these anatomical abnormalities.
What is BioPFJ™ and when is it the right treatment for patellar instability?
BioPFJ™ is a complete biological reconstruction of the patellofemoral joint using fresh donor cartilage and bone from a single matched donor — invented by Dr. Mirzayan. It is indicated for patients with recurrent patellar instability who have sustained significant cartilage damage to both the kneecap and the trochlear groove, particularly those with trochlear dysplasia. It addresses both the instability and the cartilage destruction simultaneously, corrects the dysplastic groove geometry, and eliminates the need for metal or plastic joint replacement. Dr. Mirzayan has performed this procedure in approximately 75 patients with 100% graft integration and no re-dislocations.
I had a kneecap surgery that failed and my kneecap keeps dislocating. What are my options?
Revision patellar instability surgery requires a comprehensive re-evaluation of every anatomical risk factor — because failed prior surgery almost always reflects risk factors that were not addressed at the index procedure. Dr. Mirzayan evaluates revision instability cases individually, including detailed CT and MRI analysis, and designs a revision plan that addresses the complete anatomical picture. Failed prior MPFL reconstruction is not a dead end — it is a starting point for a more complete solution.
Do you offer virtual consultations for out-of-state patients?
Yes. Please submit your MRI and CT imaging in advance so that TTTG distance, trochlear morphology, patella height, and cartilage status can all be assessed before your visit. Call (310) 746-5918 to schedule.
Does being out-of-network mean I will pay full price out of pocket?
Not necessarily. Many patients with commercial insurance — especially PPO plans and self-funded employer plans — have strong out-of-network benefits. Dr. Mirzayan's office will verify your coverage before your consultation so you have a clear picture of what to expect before making any decisions.
About Dr. Raffy Mirzayan
Dr. Raffy Mirzayan, MD is a double-board certified orthopedic sports medicine surgeon with 25 years of experience treating patellar instability at every level of complexity — from first-time dislocators managed conservatively to revision cases requiring combined osteotomy, ligament reconstruction, and biological joint resurfacing. He is the inventor of BioPFJ™ — the world's first and only complete biological patellofemoral joint reconstruction using matched fresh donor tissue from a single donor — and has performed this procedure in approximately 75 patients with outcomes published in the peer-reviewed journal Cartilage. His approach to patellar instability is grounded in a single principle: every anatomical risk factor must be identified and addressed. The surgeon who fixes only the most obvious problem while ignoring the underlying anatomy will produce a result that fails — and a revision that is harder than the original surgery needed to be. He practices at DOCS Health in Los Angeles, serves as a Clinical Professor of Orthopaedic Surgery at USC, and welcomes patients from across the United States, including Las Vegas, Phoenix, and Scottsdale, for virtual consultations and in-person care.
DOCS Health | 8436 W 3rd St #800, Los Angeles, CA 90048 | (310) 746-5918 | raffymirzayan.com
