Patellar subluxation is a long name with a simple definition. This kind of patellar tracking disorder occurs when the patella or kneecap becomes partially dislocated. Often a partially dislocated kneecap will correct itself.
When a patellar subluxation occurs repeatedly, the condition can damage cartilage on the back of the kneecap and stretch ligaments.
Causes of Patellar Subluxation
If your orthopedist has diagnosed you with patellar subluxation, you may wonder why you've developed this condition. A partially dislocated kneecap can result from several causes, including the following.
Previous Patellar Tracking Problems
Those who have experienced patellar tracking problems are more likely to experience patellar subluxations and dislocation of the kneecap.
If the patellofemoral groove at the joint of the knee and femur is too shallow or rotated, your kneecap will have an unstable base, making it more likely to be partially or fully dislocated.
Soft Tissue Malfunction
Your ligaments and tendons hold your kneecap in place. However, if your soft tissues have become stretched by previous patellar tracking problems, it becomes more difficult for them to keep the kneecap firmly in place. If the soft tissue is too tight, it can pull the kneecap out of place.
A patellar subluxation can result from an injury from participation in extreme or contact sports. After the first patellar subluxation, chances for a second partial or complete dislocation of the kneecap are higher.
Weakness of the knee and hip muscles makes it more difficult for the leg to be in proper placement. That weakness can make a patellar subluxation more likely to occur.
Poor Movement Habits
Running or jumping with the wrong leg placement can make you more likely to experience patellar subluxation. Changing direction with feet in the opposite direction can twist the knee joint to cause a patellar subluxation.
The Parts of Your Knee
The anatomy of the knee joint has the patella resting in a groove at the end of the thigh bone or femur. Your knee should slide up and down while staying in the patellofemoral groove as your knee bends and straightens.
A patellar subluxation happens when the kneecap comes partially out of this groove during movement. Often this occurs when walking on uneven surfaces or climbing stairs. Your knee will hurt more as you continue to do these activities.
The Differences Between Patellar Subluxation and Dislocation
Partial dislocation of the kneecap is much more common than patellar dislocation, or total dislocation of the kneecap.
A completely dislocated kneecap is a medical emergency and is excruciating. Typically, a kneecap is only briefly dislocated and will move back into the patellofemoral groove, but the knee will swell and still be very painful. A blow to the knee or a change of direction when the foot is on the ground, twisting the knee, can lead to a partially dislocated kneecap.
Often in a patellar dislocation, the knee dislocates sideways to the outside of the knee or laterally.
Medial and Lateral Patellar Subluxation
Patellar subluxation will either pull the kneecap toward the outside of the knee, laterally, to the inside, or medially. In either case, the kneecap does not slide within the patellofemoral groove as it should. Most of the time, a patellar subluxation is a lateral subluxation to the outside of the leg. Sometimes, though, a medial subluxation to the inside of the leg occurs.
A second medial or lateral patellar subluxation can be more likely if the first one experienced does not heal properly.
Symptoms of Patellar Subluxation
Unlike a total kneecap dislocation, which is extremely painful, a patellar subluxation may not have any symptoms. Often, a patellar subluxation feels like the kneecap is shifting out of place.
A partially dislocated kneecap will cause pain around the front or sides of the knee with activity. This condition is referred to as patellofemoral pain syndrome or PFPS.
Other symptoms of patellar subluxation include:
- Chronic knee pain that becomes worse with activity
- Knee can't support your weight and buckles
- Knee catches during movement
- Swelling and inflammation
- Cracking sounds in the knee
When To See a Physician or Specialist
Since minor patellar subluxation cases may have mild symptoms, it can be easy to put off seeing a doctor. If you have some of these symptoms or find that your symptoms are worsening, it may be time to see your physician or an orthopedic specialist.
- Knee can't bear weight or feels unstable
- Have a swollen knee
- Unable to fully extend or bend the knee to 90 degrees
- Knee looks deformed
- Have knee discomfort regularly or pain that's associated with an injury
How a Patellar Subluxation Gets Diagnosed
The first step in diagnosing a partially dislocated kneecap is an examination by your doctor. Usually, imaging aids this examination. Your doctor can tell if your knee is dislocated by an exam and through an X-ray.
Magnetic resonance imaging, or MRIs, may be used to reveal soft tissue and ligaments to your medical team for a more thorough diagnosis. Some patients may not realize they have a partially dislocated kneecap until an MRI confirms it.
How To Treat Patellar Subluxation
Just as there are several degrees of patellar subluxation going all the way to complete dislocation of the kneecap, there are many treatment options for a partially dislocated kneecap.
Treatment for patellar subluxation can include:
Treat a mild patellar subluxation with rest, elevation, ice, and anti-inflammatory medications for pain.
Exercises for patellar subluxation involve strengthening the muscles around the hip and knee so they can hold the kneecap in place more easily. Physical therapy will also target the inner thigh muscles since they will need to be as strong as the outer thigh muscles.
Carrying too much weight can strain knee joints and make patellar subluxation more likely. Weight loss is one of the most effective ways to improve stability since the knees support a force equal to one and a half times a person's weight. For example, a 200-pound man's knees face 300 pounds of force.
Exercise tape will add to the support and stability of the kneecap and decrease knee pain. Use kinesiology tape to treat or prevent patellar subluxation from happening again by wrapping the knee joint above and below the patella to hold the kneecap in place.
Wearing Knee Braces
A knee brace can help the patella move properly, staying in the patellofemoral groove. A patellar stabilizer or a patellar tracking brace can prevent patellar subluxation and provide needed support for the kneecap.
When To Consider Patellar Subluxation Surgery
Surgery is an option if nonsurgical options haven't succeeded in treating patellar subluxation. Those with severe patellar subluxation usually receive surgery to repair the root cause of kneecap dislocation. However, most patients don't consider surgery unless non-invasive therapies have not been successful.
A review of 70 previous studies concerning patellar subluxation showed that those who had surgery to treat the condition were less likely to suffer partial dislocations of the kneecap. However, it showed that these individuals were more likely to have arthritis in the affected knee.
A study from 2015 found that those who have had patellar subluxation surgery were less likely to have a complete dislocation of the kneecap later. Still, the chances of having another partial dislocation of the kneecap are about the same as those who have not had surgical treatment for patellar subluxation.
Surgical options for patellar subluxation include the following.
Lateral Release Surgery
This arthroscopic surgery realigns the kneecap and places the patella back in the patellofemoral groove. Only two small incisions are needed for this minimally invasive procedure on the outside of the knee to correct a lateral patella subluxation.
In lateral release surgery for patellar subluxation, ligaments on the outside of the knee get partially cut. This procedure prevents them from pulling the patella to the side.
This surgical option for patellar subluxation treatment tightens the soft tissue on the inner side of the knee so that it can hold the kneecap in place.
Reconstruction of the Medial Patellofemoral Ligament
If the ligament on the inside of the knee has torn through patellar subluxation, this surgery will repair the tissue, enabling it to hold the kneecap in place once again.
Tibial Tuberosity Transfer
The tibial tuberosity is a bulge in the tibia, or shin bone, just below your knee. The tendon that guides your kneecap as it slides in the trochlear groove attaches to the tibial tuberosity.
Tibial tuberosity transfer surgery involves a surgeon transferring part of the tibial tuberosity to improve the tendon's attachment. This hour-long procedure helps the knee move as it should in the groove.
Through an incision about three inches long above the tibia, a surgeon will place one or two screws inside the leg to secure the transferred bone.
Known as the Fulkerson procedure, bone realignment surgery for patellar subluxation will correct malfunctions in the leg structure that make a partially dislocated kneecap likely.
Recovery time from patellar subluxation surgery can vary since some procedures are more invasive than others. For example, bone realignment surgery has the longest recovery time, and lateral release surgery for a subluxated patella usually has the shortest recovery.
After any type of patellar subluxation surgery, you may have to use crutches. Your physician will likely give you a brace to support your knee while walking. Wearing a knee brace could be recommended for up to six weeks or more. Physical therapy may also be part of your recovery.
Most people can return to work or school about two weeks after surgery. Returning to sports will require a healing period of up to nine months.
What Patellar Subluxation Means for You
While a subluxated patella isn't a fully dislocated kneecap, it is nothing to ignore. A patellar subluxation can lead to joint damage, discomfort, and limits to activities.
A consultation with your physician or orthopedist can result in treatment ranging from rest and elevation to surgery, depending on the severity of the subluxated patella. Doctors often treat a patellar subluxation with a knee brace instead of surgery or after a surgical procedure. In either case, a knee brace can hold the kneecap and support the knee joint to allow healing.
Orthopedists often recommend physical therapy to strengthen muscles, so a second patellar subluxation is less likely.
Patellar Subluxation Final Thoughts
The first step in treating a patellar subluxation is diagnosis. If you notice any symptoms of a subluxating patella, make an appointment to see your physician or an orthopedist for a consultation. A care plan for patellar subluxation that may include rest, elevation, knee bracing, and possibly surgery will help you heal from a partially dislocated kneecap.
Ignoring symptoms of patellar subluxation will only result in pain and possible damage to the knee. Treatment will reduce pain and lead to a more active life.