Kneecap dislocation and patella instability

A kneecap dislocation can be a frightening and painful experience. The term (patella) instability covers a range of symptoms from a feeling of disease and mistrust in the knee to regular kneecap dislocation. Dislocations most often begin in the teenage years but can present at any time. However, we have made considerable advances in the treatment of this condition in recent years.

If a kneecap dislocates once will it dislocate again?

Literature tells us that after the first dislocation there is approximately a 50% chance of a further dislocation. But even if not dislocating the patella won’t be moving normally. Patients often curtail sports or even simple activities to avoid instability episodes.

What’s the underlying cause?

The underlying anatomy sets us up for a dislocation and loss of the usual restraints that lead to dislocation. Hypermobility (being double-jointed) also increases the risk. The risk factors are minor abnormalities in abnormality:

 

  • A shallow trochlear groove (this is the groove that the kneecap runs through).
  • A high patella (the patella is above the groove when the knee is in the at-risk position).
  • Rotational abnormalities (much less common).
  • The medial kneecap ligament (MPFL) was damaged by a previous dislocation.

What are the long-term effects?

There is considerable variation. Some patients recover almost fully and will have no further issues.

 

Unfortunately often the kneecap may not feel right after a first dislocation and activity levels can decline. A dislocation may be a sign that the kneecap is not tracking (moving) properly and that it will develop arthritis in later life. painful arthritis later in life. A case-controlled study (from Bristol) demonstrated an odds ratio (an increased probability) of 3.2 for developing PFJ OA severe enough for to require arthroplasty in patients with previous patella dislocations. Patients with adolescent pain symptoms had an odds ratio of 7.5.

Does physiotherapy help after the first kneecap dislocation?

Although it does not always change the course of this condition it can accelerate rehabilitation. In some cases, the benefit of physiotherapy can be very significant.

Are splint helpful?

No! They are terrible. The extension splint or cast should be avoided as this just leads to wasting of the quadriceps.

Are there any recent changes in surgical treatment?

Yes, there have been radical changes in recent years. The treatment now aims to correct the underlying anatomic problem rather than introducing a new abnormality. These include:

 

  • Trochleoplasty (reshaping the groove that the kneecap runs more smoothly).
  • Distalisation of the patella (moving the kneecap down so it sits in the groove)
  • MPFL reconstruction (reconstructing the kneecap ligament)
3d rendered medically accurate illustration of the human knee showing the anterior anatomy including kneecap dislocation, lateral collateral ligament, medial collateral ligament the position of the patella and patellar ligaments
3d rendered medically accurate illustration of the human knee showing right lateral knee anatomy including the lateral collateral ligament, the position of the patella and patellar ligaments to illustrate kneecap dislocation

What we know about kneecap dislocation

Kneecap dislocation increases the risk of knee arthritis pain occurring in the future

Kneecap dislocation can damage cartilage which is the most heavily loaded joint

There is a 50% chance of further dislocation after suffering the first kneecap dislocation

picture of a patient studying in Bristol who was treated by Damian Clark Bristol knee surgeon for knee pain including kneecap dislocation

Surgery to suit you

If surgery is required then we can determine a schedule that fits in with you and coordinate your rehabilitation appropriately.

“Mr Clark managed to fit my operation in at a time that suited me best in between exams and university… My recovery was quick and easy and I am now pain-free. Thank you, Mr Clark!”

Emma, Bristol University student

Do you fear that exercising could cause kneecap dislocation?