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Patellofemoral Surgery
Orthopedics and Traumatology

Patellofemoral Surgery

About This Department

 
Orthopedics

Patellofemoral surgery stops a kneecap that slips out of place. Arthritis behind the kneecap has its own operation.

After a first kneecap dislocation, 17 percent of patients had further episodes in a prospective study, against 49 percent of those who had dislocated before. For repeat dislocations, reconstruction of the medial patellofemoral ligament brought instability down to 1.2 percent in pooled studies, with 84 percent back to sport. Send your MRI or X-rays and a note of how many times the kneecap has come out, and our orthopedic team will tell you which operation, if any, fits.

17% vs 49%
Further instability after a first dislocation and after repeat ones
1.2%
Instability after MPFL reconstruction, pooled studies
84%
Return to sport after MPFL reconstruction
Free
Review of your scans before you book
Free consultation

The patellofemoral joint sits where the kneecap glides in a groove at the front of the thigh bone. Three problems bring patients to surgery there. A kneecap that dislocates or slips sideways, pain from a kneecap that tracks badly, and arthritis that wears the cartilage behind it.

Fewer first-time dislocators (17%) had episodes of instability during follow-up than patients with a previous history of instability (49%) (P < .01).
Prospective study of 189 patients, American Journal of Sports Medicine, 2004

Kneecap dislocation and instability

A kneecap dislocates sideways during a twist with the foot planted, and teenage girls carry the highest risk.

Some knees are built to let it happen.

  • A shallow groove on the thigh bone, trochlear dysplasia.
  • A kneecap that sits high, patella alta.
  • A shin tubercle set too far to the outside, pulling the kneecap outward.
  • Loose ligaments throughout the body.

The first dislocation tears the medial patellofemoral ligament, the MPFL, the main restraint against sideways slipping. It heals loose. Whether the kneecap comes out again then depends on the history and on the shape of the knee, and a teenager with a shallow groove and a high kneecap who has already dislocated twice faces far higher odds than an adult with a normal groove after one fall. We read the MRI with that in mind.

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Risk of the kneecap coming out again
Situation Further instability Source
First dislocation 17 percent over two to five years Prospective study, 189 patients
Previous dislocations 49 percent, odds 6.6 times higher Same study
First dislocation treated without surgery Around 35 percent at two to nine years Cochrane review, 438 patients
First dislocation treated with surgery Around 19 percent at two to nine years Same review
After a first dislocation
Most first dislocations go back in on their own or in the emergency department. An MRI within the first week shows whether a piece of cartilage has broken off. A loose fragment needs surgery to fix or remove it, and the torn ligament can be repaired at the same time. Without a fragment, physiotherapy comes first.
We are uncertain whether surgery improves outcome compared to non-surgical management as the certainty of the evidence was very low.
Cochrane review of 10 trials and 519 patients, 2023

Treating a first dislocation

Brace and crutches
A short period in a brace while the swelling settles, walking as comfort allows.
MRI
Within a week, to look for a loose piece of cartilage or bone.
Physiotherapy
Six to twelve weeks of strength work for the thigh and hip muscles that steer the kneecap.
Back to sport
Around three months, once strength and confidence match the other leg.
A high percentage of young patients return to sports after isolated MPFL reconstruction for chronic patellar instability, with short-term results demonstrating a low incidence of recurrent instability, postoperative apprehension, and reoperations.
Meta-analysis of 14 studies, American Journal of Sports Medicine, 2016

The operations

Surgery matches the cause.

This table scrolls sideways on a narrow screen. Swipe or drag to see every column.

Patellofemoral operations
Operation What it corrects Back to sport
MPFL reconstruction The torn ligament, rebuilt with a tendon graft Four to six months
Tibial tubercle osteotomy A tubercle too far out or a kneecap too high Six months
Trochleoplasty A shallow or flat groove Six to nine months
Cartilage repair A defect behind the kneecap Six to twelve months
Patellofemoral replacement Arthritis limited to the kneecap joint Low-impact sport at three months

MPFL reconstruction

The surgeon takes a hamstring tendon through a small incision behind the knee, fixes one end to the inner edge of the kneecap and the other to the thigh bone at the point where the original ligament attached, and sets its tension with the knee bent so the kneecap seats in the groove. In children with open growth plates, the thigh bone fixation sits clear of the plate. Day case or one night.

Moving the tibial tubercle

The patellar tendon attaches to a bump on the shin, the tibial tubercle. When it sits too far out, the quadriceps pulls the kneecap sideways with every step. A tibial tubercle osteotomy cuts the bump free, moves it inward or downward by around a centimeter, and fixes it with two screws.

Who needs it
A CT or MRI measures the distance between the tubercle and the groove, a figure surgeons call the TT-TG distance. Beyond around 20 millimeters, or with a high kneecap, we add the osteotomy. The bone needs six weeks to heal, and patients walk with crutches and a brace until it has.

Trochleoplasty for a shallow groove

A flat or bumped groove gives the kneecap nothing to sit in. Trochleoplasty deepens it by lifting a thin shell of cartilage and bone, removing bone beneath, and pressing the shell back into a new, deeper groove, held with absorbable tape or small anchors.

Hospital
Two or three nights, moving the knee on a machine from the first day so the new groove shapes against the kneecap.
First six weeks
Crutches with weight as comfort allows and full bending allowed.
Months three to nine
Strength work, running from four months, sport from six to nine.
Sulcus-deepening trochleoplasty performed for recurrent patellar instability in the setting of trochlear dysplasia results in improved Kujala scores and a low redislocation rate, when performed as an isolated procedure or in combination with other stabilization procedures.
Systematic review of 702 patients, Arthroscopy, Sports Medicine and Rehabilitation, 2020

Few knees need it.

Who needs a trochleoplasty
Only a minority of unstable knees. In the review of 702 patients, redislocation ran from 0 to 8 percent across studies. We keep it for severe groove dysplasia, a high-grade bump on MRI, and for knees that dislocated again after a ligament reconstruction.

Kneecap arthritis and recovery

Arthritis can wear the cartilage behind the kneecap alone, leaving the rest of the knee healthy. Pain climbing stairs, rising from a chair and squatting points to it. Old dislocations and kneecaps that have tracked badly for years lead there. So does a shallow groove. A standing X-ray with a skyline view of the kneecap shows it.

Patellofemoral replacement or total knee

A patellofemoral replacement resurfaces only the groove and the back of the kneecap, leaving the cruciate ligaments, the menisci and the two halves of the main joint untouched, so the knee keeps its natural feel and the operation stays smaller than a total knee replacement. A Danish trial randomized 100 patients with arthritis limited to that joint, with a mean age of 64.

This table scrolls sideways on a narrow screen. Swipe or drag to see every column.

Patellofemoral replacement against total knee replacement, 100 patients
Outcome Patellofemoral replacement Total knee
Pain improvement at six months, SF-36 38 points 27 points
Pain improvement at two years 39 points 33 points
Change in knee movement at two years Minus 3 degrees Minus 10 degrees
Complications No difference No difference

Recovery came faster after the partial replacement.

Recovery and the stay in Istanbul

Plan for a week or more.

How long you stay
One or two nights after an MPFL reconstruction, two or three after an osteotomy, trochleoplasty or replacement. We suggest seven to ten days in Istanbul for physiotherapy and the wound check before the flight. A companion can sleep in your room, and coordinators speaking English, Arabic, French, Russian, Serbian, Romanian or Spanish handle the airport, hotel and interpreters. The cost depends on the operations combined and the nights, and the estimate after the free review lists them.
  • Crutches.
  • A brace that limits bending in the first weeks after an MPFL reconstruction, unlocked step by step as the physiotherapist sees the thigh muscle switch back on and the swelling settle.
  • Clot prevention for the flight and the weeks on crutches.
  • Follow-up after you return home through your coordinator, with an X-ray at six weeks after an osteotomy reviewed by our surgeon.

Warning signs

Call the team the same day
A wound that leaks or reddens, a temperature of 38 degrees or more, a calf that swells and aches, sudden breathlessness, or the kneecap slipping out again.

Results after ligament reconstruction

Low recurrence, high return to sport
Schneider and colleagues pooled 14 studies of isolated MPFL reconstruction with a mean patient age of 24. Recurrent instability ran at 1.2 percent, apprehension at 3.6 percent and reoperation at 3.1 percent, and 84 percent of patients returned to sport.

Movement after a partial replacement

Two years on

Patients undergoing PFA regain their preoperative ROM, whereas patients undergoing TKA at 2 years have lost 10° of ROM.
Danish randomized trial of 100 patients, 2018

Patellofemoral surgery FAQ

Do I need surgery after my first kneecap dislocation?
Usually not. Physiotherapy comes first, unless an MRI shows a loose piece of cartilage, or the shape of your knee puts you at high risk of another dislocation.
How long until I can play sport again?
Four to six months after an MPFL reconstruction, and longer when an osteotomy or trochleoplasty is added.
Can a teenager have the operation?
Yes. In children with open growth plates, the surgeon places the fixation on the thigh bone clear of the plate.
Is a patellofemoral replacement better than a total knee?
For arthritis limited to the kneecap joint, a randomized trial found faster recovery and better movement at two years after the partial replacement.
Can my mother or father stay with me?
Yes. One parent or companion stays in your room for the whole admission, which matters most for teenage patients.

References

  1. Fithian DC, Paxton EW, Stone ML, et al. Epidemiology and natural history of acute patellar dislocation. American Journal of Sports Medicine. 2004;32(5):1114-1121.
  2. Smith TO, Gaukroger A, Metcalfe A, Hing CB. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane Database of Systematic Reviews. 2023;1(1):CD008106.
  3. Schneider DK, Grawe B, Magnussen RA, et al. Outcomes after isolated medial patellofemoral ligament reconstruction for the treatment of recurrent lateral patellar dislocations: a systematic review and meta-analysis. American Journal of Sports Medicine. 2016;44(11):2993-3005.
  4. Davies MR, Allahabadi S, Diab TE, et al. Sulcus-deepening trochleoplasty as an isolated or combined treatment strategy for patellar instability and trochlear dysplasia: a systematic review. Arthroscopy, Sports Medicine, and Rehabilitation. 2020;2(5):e661-e669.
  5. Odgaard A, Madsen F, Kristensen PW, Kappel A, Fabrin J. The Mark Coventry Award: patellofemoral arthroplasty results in better range of movement and early patient-reported outcomes than TKA. Clinical Orthopaedics and Related Research. 2018;476(1):87-100.

Editor's note

Written by the Biruni Hospital medical editorial team. Reviewed by Assoc. Prof. Dr. Suat BATAR, Orthopedics and Traumatology.

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