Knee Cap Dislocation

Dislocated patella or popping patella

Perth knee surgeon | Orthopaedic surgeon Dr David Colvin - shoulder and knee surgery

Dislocated knee cap

Knee surgeon perth

What is a knee cap dislocation?

Knee cap dislocation, also known as patella dislocation, occurs when the knee cap is completely displaced out of its normal position. The knee cap runs in a groove on the front of the femur, called the trochlea.

When the knee cap is knocked out of this groove, a dislocated patella always goes to the outer (lateral) side of the knee. As a result, the muscles on the inner side of the knee are damaged and the ligaments can be torn or stretched.

Dr. David Colvin, trained in orthopaedic surgery in Perth. David's specialty is knee and shoulder surgery and sports injuries.

About Dr Colvin

What causes knee cap dislocation?

Patella dislocation is caused by a direct blow to the front of the knee or from a sudden pivoting of the leg, forcing the knee cap to the outside. Some people are more at risk of patella dislocation.  Risk factors include:

  • Maltracking or tilt of the patella.
  • Being generally loose jointed.
  • Being knock kneed.
  • Having a high knee cap.
  • Being born with a shallow groove for the knee cap (shallow trochlea).

Patella maltracking is a very common problem.  Even a normal knee cap has a tendency to run towards the outer half of the groove. In some people this can be quite severe, resulting in maltracking and patella tilt.  Sometimes the patella does not completely dislocate. It may feel like it is partly slipping out, which is called patella subluxation.

What are the symptoms of knee cap dislocation?

A knee cap dislocation is a very dramatic event which causes sudden severe pain and an inability to straighten the knee.

Usually the knee cap is visible sitting in a very abnormal position on the outer half of the knee.  If you straighten the knee, the patella may come back into its normal position with a sudden clunk.

A small number of people dislocate their patella and it comes back into position immediately. They may not even be aware that the knee cap was dislocated briefly. It may be necessary to go to hospital to have the knee cap put back into place.

Even once it’s back in place, the knee usually becomes very sore and swollen over the following days.

Some people experience patella subluxation where it partially dislocates and then comes back into position spontaneously. This can be very unnerving and the knee can feel like it’s going to give way


CO.RE Exercises

knee cap dislocation | Perth Knee Surgeon

In the field of shoulder and knee reconstruction, successful outcomes from an operation are 50% surgery and 50% rehabilitation. You could say the surgery is the easy bit, the rehabilitation is all hard slog. Dr Colvin’s CO.RE exercise programs are just that, a core plan for your successful recovery.

Choose your program

Orthopaedic surgery for knee cap dislocation

Repeated patella dislocation or subluxation usually requires patellofemoral reconstruction surgery. There are two treatments for this type of knee injury.

Dr Colvin may recommend a Tibial Tubercle Transfer (TTT or Triple T). This involves cutting and shifting the bone where the patellar tendon attaches to the tibia, to centralise the knee cap.

The alternative procedure is called a Medial Patellofemoral Ligament Reconstruction (MPFL Reconstruction). This reconstructs the torn ligaments on the inner half of the knee that hold the patella in place. In some cases, both procedures are performed at the same time.

Dislocating knee cap? Make an appointment for advice

When you book your appointment with Dr Colvin, he will tell you more about the surgical treatment options for a dislocating knee cap or patellofemoral subluxation here at our Perth practice (SJOG Subiaco).

MPFL Reconstruction

The knee cap or patella acts as a pulley at the front of the knee. It allows the large quadriceps muscles of your thigh to pull across the front of the knee acting on the patellar tendon to straighten the knee. The patellar sits in a groove at the front of the femur (thigh bone) called a trochlea groove. With a direct blow or a twisting injury, the patella can be dislocated out of its groove onto the outside of the knee joint.
mpfl reconstruction medial patellofemoral

Tibial Tubercle Transfer

Tibial Tubercle Transfer (TTT) is what orthopaedic surgeons call a realignment procedure. Think about how we straighten the knee. The quadriceps muscles on the front of the thigh contract. They pull on the patella, which is connected to the tibia (shin bone) by the patellar tendon, and the knee straightens. This works well when everything is nicely centred at the front of the knee.
tibial tubercle transfer surgery ttt

Kneecap Pain

A sore knee cap is a very common complaint in all age groups. One in three people experience knee cap pain at some stage. Typically this pain is experienced at the front of the knee. The knee cap, also known as the patella, with doctors referring to the type of pain as “patellofemoral pain”.
knee cap pain

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Suite 213/25 McCourt St,
Subiaco WA 6008


Monday to Friday 8:30am to 5.00pm AWST

Consulting Rooms

Dr David Colvin consults at:
Western Orthopaedic Clinic

  • These rooms are part of St John of God Subiaco Hospital.
  • Parking is available on site.


Dr David Colvin operates at:
St John of God Subiaco Hospital
12 Salvado Rd,
Subiaco WA 6008