The retinaculum is the fibrous web-like network on the medial (inner) and lateral (outer) aspects of the kneecap. The lateral retinaculum is a powerful lateral stabiliser of the knee.

In the 1970’s two surgeons, Merchant and Mercer, published a paper called “Lateral Release of the Patella: A Preliminary Report”. This popularised surgery to cut or ‘release’ the lateral retinaculum and it soon became a panacea for any type of anterior knee pain. Because of the improper use of this procedure for the wrong indications, complication rates soared.

The operation was being used to treat patellar instability and all too often resulted in worsening of the situation to include weak vastus lateralis muscle (one of the quads muscle heads) and a switch from the kneecap being unstable to the outer side to it being unstable to the inner side (medial subluxation or even dislocation).

After years of gathering scientific data it became clear that the only true indications for this surgery were:

  • patellar (kneecap) tilt in association with anterior knee pain
  • excessively tight lateral reticular tissues

The cause of anterior knee pain is not always clear - the pain may come from nerve fibres supplying the bone beneath the cartilage covering under the patella, from nerves in the fat pad deep to the patella or to nerve fibres in the medial retinaculum.Physical examination for anterior knee pain should include examination of the knee in extension, with examination of the fat pads, the medial and lateral retinaculum (including the medial plica) and tests for hypermobility, in addition to standard tests for patellar tracking. In cases associated with instability the patellar apprehension test is often positive.

To determine the presence of patellar tilt, one may do a plain film x-ray “sunrise” view which allows the patella to be accurately and easily measured to evaluate the degree of tilt. The X-ray is taken at a special angle and the film shot as to appear as a “sunrise”.​ CT scan and MRI scan will also show this but they are more expensive.


I took a look at a number of bulletin boards dedicated to lateral release discussions and found a typical pattern. Here are three of them -

  • Female of unknown age had Arthroscopic Lateral Release 2 years prior to treat knee swelling and patellar instability. Describes the Lateral release as “the worst mistake of my life” and is having worsening instability after the surgery and continued swelling. 

  • Female of unknown age had a Lateral Release for an unknown diagnosis. She develops patellar subluxation and “knee giving way” as well as a “knife like pain” that is far worse than any symptoms preoperatively.

  • 19 year old female 3 months post op from an Arthroscopic Lateral Release for a long history (more than 5 years) of bilateral knee swelling and knee pain. She is an avid swimmer, on swim team and also a runner. The pain was interfering with her activities so she saw an orthopedic surgeon.The orthopedic surgeon diagnosed her with a “tilted patella” (an appropriate indication if that was truly the diagnosis).The orthopedist initially treated her with conservative therapy with steroid injections, with short-term improvement. Her orthopedist told her the only option was to have a Lateral Release (it is unclear whether she had an open or arthroscopic procedure) and the doctor “also removed some scar tissue” though she had had no prior surgery and had a MRI that did not show any abnormality per her report. At 2 months post op she develops a large effusion of the knee and this is drained. At three months post op she is having trouble and unable to extend her leg fully and has a feeling of her knee being very “tight”. She is wondering whether she may have arthrofibrosis? Currently she cannot do any of the activities she had done prior to surgery.


Michelle Boucher


The only true indications for a lateral release procedure in adults are patellar tilt and excessively tight lateral retinaculum. Surgeons still perform the procedure for other indications such as lateral patellar compression syndrome without tilt and patellar instability. This is particularly unfortunate as it has such a high complication rate of patellar subluxation and dislocation. This procedure should be approached rather judiciously by the patient, and with a second opinion, given that the complications are sometimes far worse than the actual problem they had initially seen the surgeon about, often times vague anterior knee pain. In my opinion the lateral release procedure still continues to be performed far too often and without sufficient understanding of the exact pathology leading to debilitating complications and even additional surgeries to correct the damage done with the LR procedure.