Patellofemoral Disorders


The patellofemoral (kneecap) joint is made up of two bones: the patella (the kneecap) and the femur (the thighbone). When the knee bends and straightens, the patella glides along a groove on the femur called the trochlea. Some people have differences in the way the kneecap and this bone fit together.

These variations can lead to problems with the patellofemoral joint. For example, when the patella sits too high in this groove, the patella is prone to dislocations. Altered alignment may also cause the joint surfaces to wear down, which can cause pain.

Problems in the patellofemoral joint can be divided into several groups:

Chondromalacia Patellae

The undersurface of the patella is lined with cartilage. This cartilage provides a smooth surface for the patella to glide during knee movement. Chondromalacia is a condition that occurs when this cartilage breaks down. The pain may be along the sides of the patella or it may feel like it is deep inside the knee. Feelings of crunching or noise in the knee are an indication of chondromalacia.

Treatment of Chondromalacia Patellae

Treatment focuses on emphasizing full range of motion and strength.

Rehabilitation will also address any muscle imbalances that may be contributing to the patellofemoral pain. In some rare cases, a knee arthroscopy may be necessary.

Patellar Malalignment

Patellar malalignment occurs when the patella does not contact the femur in an ideal position. The patella can sit too high or too far toward the outer (lateral) side of the knee. People who have patellofemoral pain often complain of pain after sitting for prolonged periods and with stair climbing. This malalignment can be congenital or the result of a traumatic injury.

Treatment of Patellar Malalignment

Problems with the alignment of the patella may require surgery. This can be determined on an individual basis after an evaluation by Dr. Shelbourne, or Dr. Benner. Rehabilitation focuses on restoring full, symmetric range of motion and strength.

Patellar Subluxation/Dislocation

Some people experience episodes where their patella will dislocate, or slip to the side. Usually swelling, stiffness and pain are symptoms that follow these injuries. At first, treatment will focus on minimizing the swelling, walking normally without a limp, and restoring full range of motion. Once range of motion is full and the swelling has resolved, treatment will focus on strengthening. Sometimes surgery is required following a patellar dislocation.

Treatment of Patellar subluxation/dislocation

Patella subluxation/dislocation historically has been difficult to evaluate and treat because of a lack of understanding of the anatomy and the underlying problem and causes of patellofemoral malalignment, dislocations, and subluxation.

The patellofemoral malalignment is a relatively uncommon disorder. However, because all we see our knee problems, we have been able to research and better understand this problem and develop our current concept about the diagnosis and treatment.

There are several factors we evaluate in order to diagnose patellofemoral malalignment and develop the right treatment plan on an individual basis after evaluation.

Patella Realignment

Patellar (kneecap) realignment procedures are used to treat instability problems at the kneecap joint. Patients with instability of the kneecap suffer from dislocations or feelings of their kneecap slipping. Many times, patients with instability of the kneecap have problems with the alignment of the kneecap where the knee cap is not centered in the groove of the thigh bone. The patella sits more toward the outside (lateral) side of the knee, which makes it easy to slip out of the joint with twisting and pivoting. Some people are born with abnormal alignment of the kneecap and it becomes bothersome after an injury. Other people are born with normal alignment, but develop problems after an injury to their kneecap.


Before surgery- knee cap is aligned too far to the outside of the knee

The goal of patellar realignment surgery is to bring the kneecap back into a normal alignment. There are several different surgeries that can be done to realign the kneecap. Your surgeon will make the determination of which procedure is right for you on a case-by-case basis.


After surgery: kneecap is centered


All patellar realignment surgeries begin with an arthroscopy (scope). This procedure is used to examine the knee joint and look for damage to the cartilage surfaces of the bones. The trauma from a patella dislocation can cause damage to the cartilage. If necessary, these injuries are treated at this time.

Types of Patellar Realignment Surgeries

Following the scope, the surgeon will perform the procedure to re-center the patella. The realignment surgeries can be divided into two types.

  • Proximal repair: Involves repairing the soft tissue near the kneecap.
  • Distal repair: Involves moving the insertion of the patellar tendon to the tibia (shin bone) and is called a Trillat procedure.

The goal of both of these surgeries is to bring the kneecap to a centered position.

Proximal repair

Proximal repair is a repair above the knee joint. The proximal repair requires the surgeon to make a small (about 2-3 inches long) incision on each side of the kneecap. The kneecap is stabilized by soft tissue called the retinaculum. After a patella dislocation, the retinaculum on the inner side of the knee is torn or stretched. Also, the retinaculum on the outer side of the knee shortens when the knee cap is not in a centered position. The proximal repair procedure tightens the retinaculum on the inner side of the knee and loosens the retinaculum on the outer side of the knee. This brings the patella back to a centered position.

Distal Repair

A distal repair is a repair below the knee joint. The distal repair (Trillat procedure) requires one incision on the upper part of the tibia (shin bone). This is the area where the patellar tendon inserts into the tibia. This area of bone is slightly elevated from the rest of the tibia and is called the tibial tubercle. The procedure involves removing the tibial tubercle from its original position and moving it slightly to the inside (medial side) of the knee. This new position re-centers the kneecap into the groove.

A plate and screws are used to keep the tibial tubercle in this new position.

Physical Therapy after Patella Realignment Surgery

After surgery, our rehab program will help you recover and return to your normal activities and sports.

The goals for rehabilitation are to:

  • Control swelling.
  • Regain full knee extension.
  • Regain full knee flexion.
  • Return of full leg strength and function.

Help Us Improve Care for Other Patients

We have treated over 700 patients who needed a patellar realignment and they have been a part of our ongoing research to determine outcomes after surgery. Results show the surgeries were successful for restoring stability and function. (Click here for Patellofemoral publications)

If you choose Shelbourne Knee Center for your care, we hope you will be part of our research so we can help other patients in the future.

You can do this by taking our annual survey and coming back for free follow-up visits at:

  • 2 years after your surgery.
  • 5 years after your surgery.
  • 10 years after your surgery.
  • 15 years after your surgery.