What is the patellofemoral syndrome?

The patellofemoral pain syndrome or anterior knee pain manifests as pain in the anterior aspect of the knee and is reckoned to generate 50% of all knee pain. Although the origin of this pain is not well known, it is thought that it is generated by irritation of the synovial tissue that surrounds the joint.

The patella or kneecap is a bone that has very special characteristics. It is supported at all its edges by muscles and ligaments, sliding into the trochlea or the sulcus femoralis. Patellofemoral instability presents when this mobility is abnormally increased and it may or may not be accompanied by pain.

The pain is generated after an increase in pressure between the patella and the trochlea. The more the knee is flexed, especially if done loading weight on it, the greater the pressure that can generate irritation and wear on the articular cartilage. That is why this pain presents so characteristically upon coming down or climbing stairs or by spending a great deal of time with the knees bent.

Predisposing factors

Although the pain starts spontaneously for no apparent reason in a high percentage of patients, there are factors that predispose to the patellofemoral pain syndrome in most cases:

  • When the patella is not centered symmetrically in the trochlea, an imbalance that leads to irritation and cartilage wear is generated.
  • Excess of negative activities for patellofemoral pain.
  • Genu valgus (see osteotomies).
  • High riding patella or patella alta, increase in the relationship between the sulcus femoralis and the insertion of the patellar tendon, external torsion of the patella.
  • Joint hiperlaxity.
  • Patellar dislocations.
  • External tibial torsion.
  • Flatfoot.
  • Weak medial vastus muscle (inner zone of the quadriceps muscle).
  • Knee injury.


There is very little pressure between the patella and femur when the knee is extended or minimally bent. Therefore, the best activities are those that limit flexion to 45°.  


It is based on two principles: reduce inflammation and improve the dynamic between the patella and femur. 

Only in those cases of a painful and swollen knee. The pain should be the guide for the conduct of activities. Some discomfort or bother is not a problem, rest only when there is pain.

It is recommended in the initial periods, especially at the end of the day or sports activity. It should be applied for about 15 minutes each time.

Nonesteroidal anti-inflammatories drugs
With the same objective as rest and ice, that is, to reduce inflammation and pain.

It is without doubt the essential element of any treatment of patellofemoral pain. Up to 95% of patients improve with correctly performed rehabilitation. Keep in mind that if the thigh muscles are strong, the patella will move within the sulcus femoralis with less pressure. Unfortunately, it is usual to see them being done improperly as well as the lack of continuity with the exercises by patients. In general, the lack of detailed medical information generates an incorrect execution of the exercises by the patient that does not yield any improvement. This generates disappointment that leads patients to abandoning the routines.

Exercises should be done at least 4 times a week with maximum intensity, about 30 minutes per session. There are three essential types of exercises to execute:

  • Isometric quadriceps
  • Hamstring stretches
  • Hip adductors and rotators
  • Strengthening of the abdominal core


A small percentage of patients will need surgery to treat the pain and/or patellofemoral instability. This is generally indicated by the failure of a treatment based primarily on exercises, correctly performed for at least about 3-6 months. There are exceptions to this rule such as in the repeated or recurrent patellar dislocation. The choice of the multiple available surgical techniques to be performed is based on the specific alterations of each patient:

  • Increase in the patellar tilt.
  • Patella alta.
  • Increase in the TTTG distance (relationship between the trochlea and patellar tendon).
  • Trochlear dysplasia (flat sulcus femoralis).
  • Tear of the medial patellofemoral ligament.
  • Retraction of the lateral patellar wing.
  • Patellofemoral arthrosis.

These are determined by means of a physical exam and by imaging studies such as CT scans and standard x-rays. The role of the MRI in patellofemoral pathology is secondary.

Given the observed changes, surgical options are usually found among:

  • Release or lengthening of the lateral retinaculum (for open or arthroscopic surgery).
  • Distal transfer of the patella.
  • Medialization with or without anteriorization of the tibial tuberosity.
  • Patellar remodeling.
  • Oblique medial vastus muscle advancement or patellar reefing.
  • Patellofemoral prosthesis.
  • Reconstruction of the medial patellofemoral ligament.
  • Trochleoplasty (remodeling of the sulcus femoralis).

Each of these techniques can be done alone or associated with each other.

Medial patellofemoral reconstruction is currently considered the crucial step in any patellar instability surgery. It may be associated to additional surgical techniques. However, this ligament needs to be always reconstructed.

After surgery

On the day of hospital discharge and before leaving for home, the patient receives all necessary information regarding postoperative care . The patient also leaves the hospital with an appointment for within 10 days or so to have the wound checked and have the stitches removed.

see post-operative care


The type of rehabilitation varies depending on the surgery performed, but it is always centered on the same principles previously described. It is that of strengthening the quadriceps and hip rotators, and stretching the hamstrings (see videos). Most patients achieve almost complete functional improvement between 3 and 6 months, although less additional progress is to be expected until one year of the intervention.