If you have patellofemoral (patellar) instability, you’re at risk of frequent kneecap dislocations. The condition can also put you at risk of cartilage damage, which can lead to arthritis.
Surgery can address patellar instability by stabilizing the kneecap and repairing damaged cartilage. This surgery can help prevent future problems.
Learn more about patellar instability and what procedures can fix it from John Kunkel, DO, orthopaedic sports medicine surgeon, UPMC in North Central Pa.
What Is Patellofemoral (Patellar) Instability?
Your patella (kneecap) sits in a groove on the femur known as the trochlea. Patellofemoral (patellar) instability is when the patella moves out of the groove either partially (patellar subluxation) or completely (patellar dislocation).
Patellar instability often starts with a traumatic patellar dislocation, such as a sports injury. Patellar dislocations account for about 3% of all knee injuries and are more common in younger athletes.
“It usually starts with one dislocation where the kneecap slides out to the side, and that’s usually a pretty traumatic experience,” Dr. Kunkel says. “The kneecap is kind of stuck on the side of the knee, and it looks very gruesome.
“And then it gets difficult to reduce it and get it back up top, so often, the person’s knee is locked in place, and they can’t move it. So sometimes they have to go to the emergency department and get some sedation medicine to fully be able to get it back in place.”
Chronic patellar instability can develop if the initial injury isn’t properly addressed or because of anatomic factors. These issues can cause more frequent patellar dislocations. Down the line, that could lead to long-term problems like chronic pain and arthritis.
“They develop more chronic instability to where they could just be walking up or down the stairs, and it’ll pop out,” Dr. Kunkel says. “They just kind of push it back in, and it gets very easy to come out and in and out and in.
“The problem with that is we really start wearing down knee cartilage each time it comes out. The cartilage is what really determines the life of your knee and whether you’re going to be able to have a non-painful knee in the future.”
Patellar instability risk factors
Anatomic factors can put people at greater risk of patellar instability. For example, Dr. Kunkel says women are at greater risk because of what’s known as “the Q angle.”
“It really just means the female pelvis is a little bit wider, so the angle of the quadricep muscle going down the front of the leg is a little bit wider,” Dr. Kunkel says. “What that does is it pulls that kneecap a little bit more to the outside. And when a kneecap dislocates, it’s usually to the outside.”
Other people may be at greater risk because of how their patellar tendon attaches to their tibia (shinbone), Dr. Kunkel says.
Patellar Instability Surgery
Surgery is not always necessary for a first-time patellar dislocation. But in the case of chronic patellar instability, surgery can help stabilize the knee and prevent future dislocations.
The main procedure for patellar instability is a reconstruction of the medial patellofemoral ligament (MPFL). Dr. Kunkel often combines it with a bone-cutting procedure called an osteotomy, which can fix misalignment. He also may perform cartilage restoration procedures to fix damaged cartilage.
Magnetic resonance imaging (MRI) scans can show the anatomy of the leg to determine what procedures are needed.
MPFL reconstruction with osteotomy
The medial patellofemoral ligament (MPFL) connects the patella to the femur and helps stabilize the patella. This ligament typically tears during a patellar dislocation. Reconstruction of the MPFL can help prevent future dislocations, particularly when combined with a bone-cutting procedure called an osteotomy.
MPFL reconstruction entails using a graft — such as a hamstring or quadriceps tendon — to reconstruct the ligament. This can keep the kneecap from sliding to the side and dislocating in the future.
Osteotomies are procedures where the surgeon cuts a bone to fix the alignment of the leg. They can address anatomical problems that may be causing the patellar instability. Osteotomies that can take place with an MPFL include:
- Distal femoral osteotomy — A cutting of the bottom portion of the femur to fix alignment.
- Tibial tubercle osteotomy — A cutting of the area where the patellar tendon connects to the tibia to correct the alignment.
In addition to the MPFL reconstruction and osteotomy, a surgeon may perform cartilage restoration procedures. They can help repair cartilage that was damaged by frequent patellar dislocations.
Recovery from Patellar Instability Surgery
Full recovery from MPFL reconstruction plus osteotomy and cartilage restoration can take anywhere from several months to over a year. It depends on the procedures performed and the patient’s previous activity level. If cartilage restoration was performed, recovery can take longer. And the rehabilitation process for returning to sports is typically longer than the process for returning to everyday activities.
Patients are typically on crutches to avoid weight-bearing for at least six to eight weeks after surgery. After that, they may increase activity and weight-bearing at a slower pace than other knee injuries.
“The patellofemoral cartilage can sometimes be a longer rehab just because of the amount of motion that happens in that joint,” Dr. Kunkel says. “The patella is constantly sliding back and forth on the femur. And so, if we’re working on cartilage on the undersurface there, we have to slow them down a little bit early to really protect it, but then that causes stiffness.
“So, they have to work a little bit harder and longer to get their motion back, which delays the rehab timeline a little bit.”
Patients should discuss their physical therapy and recovery plan with their surgeon.
Patellar Instability Surgery Results
Surgery to correct patellar instability can stabilize the patella and fix the leg’s anatomy to prevent future kneecap dislocations. It can allow people to return to sports or daily activities without the worry of frequent dislocations.
“I’ve had collegiate athletes who are trying to get back to college soccer, and they just can’t because they keep having pain and instability, and they can’t run, and they can’t cut,” Dr. Kunkel says. “Then I do this procedure and stabilize their kneecap and restore their cartilage, and they get back to being able to play soccer with a pain-free knee.
“And then to the other end of the spectrum, somebody who might be in their 40s with instability, day-to-day, they’re walking up and down stairs or squatting down to pick something off the floor, and their kneecap keeps popping out of place. And so you do this procedure, and now they can do all their daily activities, and they don’t have that constant instability.”
The cartilage restoration also can help prevent long-term problems like chronic pain and arthritis, Dr. Kunkel says.
Choosing UPMC for Patellar Instability Care
UPMC’s orthopaedics and sports medicine teams provide expert care for conditions like patellar instability. Our surgeons can perform advanced procedures to help you return to your sport or your daily activities.
With locations throughout Pennsylvania and in western New York, you can get the care you need close to home. For example, Dr. Kunkel performs advanced procedures for people who live in north central Pennsylvania.
To find a UPMC orthopaedics and sports medicine location near you, visit our website.
Sources
American Academy of Orthopaedic Surgeons, Patellar (Kneecap) Instability. Link
Christopher Jayne, MD, Sophia Mavrommatis, BS, Ayush D. Shah BS, Journal of the Pediatric Orthopaedic Society of North America, Risk Factors and Treatment Rationale for Patellofemoral Instability in the Pediatric Population. Link
Steve Wolfe, Matthew Varacallo, Joshua D. Thomas, et al, StatPearls, Patellar Instability. Link