Patellar Subluxation (Kneecap Dislocation)

Your knee is the largest joint in your body and it joins your leg with the thigh. Each knee has 2 joints, one between the femur and patella (patellofemoral joint) and one between the femur and tibia (tibiofemoral joint). 

One of the most common knee injuries in children and adolescents, as well as in some adults is patellar subluxation. Surgery is normally not required for the first occurrence, however, if it is needed, then several new techniques make it likely that you will regain all or most of your previous activity and strength. If you are unable to straighten or bend your knee and put weight on your leg or walk, then you should consult your healthcare provider for further advice. 

What is Patellar Subluxation?

Another term for a bone’s partial dislocation is subluxation. Patellar subluxation is a partial dislocation of the patella (kneecap). It is also known as kneecap instability or patellar instability. 

The kneecap is a small protective bone that attaches near the femur (bottom of your thigh bone). The trochlea, a groove at the bottom of the thigh, is where your kneecap glides up and down when you straighten and bend your knee.

Several groups of ligaments and muscles hold your kneecap in place. When these become injured, your kneecap might move out of the groove, causing difficulty and pain in flexing the knee.

The extent of the dislocation determines whether it is called a dislocation or a patellar subluxation. 

The majority of injuries force the kneecap to move toward the outside of the knee. This can also damage the ligament on the inside of the knee, known as the MPFL (medial patellofemoral ligament). A second dislocation may occur if the MPFL does not heal adequately.

What are the Symptoms of Patellar Subluxation?

You might experience the following symptoms with patellar subluxation:

• Swelling or stiffness of the knee
• Cracking or popping in the knee
• Knee pain in the front that becomes worse after exercise
• Pain after extended sitting
• The kneecap moves from the inside of the knee to the outside
• Locking, catching or buckling of the knee

Although you may be able to self-diagnose, you will need to see a doctor for treatment.

You Can Also Read: Arthritis of Knee: Symptoms & treatment

What are the Causes of Patellar Subluxation?

Any contact sport or extreme activity can cause a patellar subluxation.

Dislocations and patellar subluxations mainly affect active and young people, especially between the ages of ten to twenty years. Most first-time injuries occur during sports.

The chances of a second dislocation are very high after an initial injury. 

How is Patellar Subluxation Diagnosed?

To diagnose a patellar subluxation, your doctor will straighten and bend the injured knee and feel the area around the kneecap.

X-rays might be used to see how the kneecap fits into the groove at the bottom of the patella and to identify any other possible bone injuries.

MRI (magnetic resonance imaging) might be used to visualise the ligaments and other soft tissue around the patella. Adolescents and children are sometimes not aware that they have had a patellar dislocation. The MRI can help confirm it.

What is the Treatment for Patellar Subluxation?

There are 2 types of treatment for patellar subluxation – surgical and non-surgical. 

Non-Surgical Options

Nonsurgical treatment is recommended for the majority of people with a first-time patellar dislocation or subluxation. 

Nonsurgical treatment includes:

• Specialised footwear to relieve kneecap pressure
• Casts or braces to immobilise the knee
• A cane or crutches to take the weight off the knee
• Physical therapy
• NSAID (nonsteroidal anti-inflammatory drugs)
• RICE (rest, icing, compression, and elevation)

You have about a 33% chance of recurrence after a patellar subluxation. 

Surgical Options

The majority of first-time patellar subluxation instances don’t require surgery and are managed conservatively. Surgical treatment is recommended in special cases or if you have a repeat episode.

Some common types of surgery for repeat episodes of patellar dislocation or subluxation are:

• MPFL (Medial Patellofemoral Ligament) Reconstruction

The MPFL (Medial patellofemoral ligament) pulls the kneecap toward the inside of the leg. When the ligament is damaged or weak, the kneecap can dislocate toward the outside of the leg. 

MPFL reconstruction is an arthroscopic surgery involving 2 small incisions. In this procedure, the ligament is rebuilt using a little piece of tendon taken from either your or a donor’s hamstring muscle. It takes about 1 hour. You normally return home the same day wearing a brace to stabilise your knee. 

The brace keeps your leg straight while walking. It is worn for 6 weeks. After 6 weeks, you begin physical therapy. Most people can resume sports and play activities 4 to 7 months after MPFL reconstruction.

• Tibial Tuberosity Transfer

Your shin bone is also known as your tibia. The tibial tuberosity is a bulge or an oblong elevation, in the tibia just below your knee. 

The tibial tuberosity receives an attachment from the tendon that controls the motion of your kneecap in the trochlear groove. An injury that has caused the kneecap to dislocate might have damaged the connection point for this tendon.

Tibial tubercle transfer operation requires an incision about 3 inches long above the shin bone. In this procedure, your doctor moves a small portion of the tibial tuberosity to enhance the tendon’s adhesion. This then facilitates correct kneecap movement inside its groove.

The surgeon will place 1 or 2 screws inside your leg to secure the piece of bone that is transferred. The operation takes about 1 hour.

You will be given crutches to use for 6 weeks following surgery. After that, physical therapy begins. Most people can return to school or work 2 weeks after surgery. It takes about 9 months before you can return to sports.

• Lateral Release

Until about ten years ago, lateral release was the standard surgical treatment for patellar subluxation, but it is rare nowadays because it increases the risk of recurrence of instability in the kneecap. 

To stop them from dragging the kneecap to one side during this treatment, ligaments on the outside of the knee are partially severed.

Conclusion

Patellar subluxation is a common knee injury. Surgery is not required initially as you can try non-surgical treatment, however, if you still face difficulties in knee movement, then it is always advisable to seek medical help from an experienced orthopaedist. Timely care and help can ensure an appropriate diagnosis and treatment of your condition. 

At the CK Birla Hospital, we ensure patients get holistic medical support which includes treatment in a compassionate environment. This patient-centric approach not only helps patients heal better but also ensures they are aware of the preventive measures as well. In case you need to consult an orthopaedist, reach out to us, or book a direct appointment with Dr. Anuj Chawla at the CK Birla Hospital.

FAQs

Is Patellar Subluxation Painless?

With chronic patellar subluxations, the pain might be less severe than in a traumatic injury. Patients might complain of pain underneath the kneecap, especially with activities that involve deep knee bending.

Is Patellar Subluxation Permanent?

A minor subluxation of the patella, especially if it is not a first-time subluxation, might recover fairly quickly with full recovery in a few days to a few weeks. Ongoing physical therapy and a kneecap stabilising brace might be required for a full recovery and to prevent a recurrence of the injury.