Overview

The patellofemoral joint is a complex joint at the front of the knee, formed by two bones: the patella (kneecap) and the front portion of the femur (thigh bone), just beneath the kneecap. The patella sits within a groove on the femur known as the trochlea, and this joint relies on a delicate interplay of muscles, tendons, ligaments, and bony anatomy to function correctly. A problem with any one of these components can lead to pain and instability around the patellofemoral joint.

Patellofemoral instability is a debilitating condition. It occurs when the kneecap fails to track correctly within the trochlear groove — either feeling as though it's about to slip out to the side when bending the knee (instability), or actually moving out of place (dislocation). This condition can significantly limit daily life, making it difficult to take part in sport or, in more severe cases, even to walk comfortably.

It most commonly presents in two groups: teenage girls with a developmental predisposition to instability around the joint, and adult male and female athletes who develop instability following a knee injury.

What causes patellofemoral instability / dislocation?

The causes of patellofemoral instability generally fall into two categories: developmental and traumatic.

Developmental causes relate to an underlying abnormality in the structure of the joint, which may include:

  • A shallow trochlear groove (trochlear dysplasia)
  • A high-riding kneecap (patella alta)
  • An abnormal attachment of the patellar tendon to the shin bone
  • Knock-kneed alignment of the legs

Traumatic causes occur when the joint's anatomy is otherwise normal, but an injury has caused damage — most commonly a rupture of the medial patellofemoral ligament (MPFL), which plays a key role in keeping the kneecap correctly positioned.

Symptoms

Symptoms of patella dislocation can include:

  • Pain in the knee
  • Swelling in the knee
  • Difficulty straightening the leg
  • Knee instability or the feeling that the knee is "giving out"
  • Visible deformity of the knee
  • Difficulty bearing weight on the affected leg

If you suspect that you have a patella dislocation, you should seek medical attention as soon as possible. The longer a patella dislocation goes untreated, the more likely it is to become a recurrent problem.

Treatment 

Treatment for patella instability depends on severity and underlying cause. Non-surgical options include physiotherapy to strengthen and stabilise the muscles around the knee, bracing to support the patella, and NSAIDs to manage pain and inflammation. Following the treatment plan closely gives the best chance of success.

If conservative measures aren’t sufficient, surgery may be needed — with the specific procedure tailored to the underlying cause. Options include:

  • Lateral release — Releasing tight tissue on the outer knee to let the patella move more freely.
  • MPFL reconstruction — Rebuilding the key inner-knee ligament that stabilises the patella, using tissue from elsewhere in the knee or a synthetic graft.
  • Tendon transfer — Repositioning a tendon to help hold the patella in place.
  • Osteotomy — Realigning the bone around the patella to correct its position.

Frequently asked questions

We carry out a thorough clinical examination of the knee, along with a routine MRI scan, to assess the joint’s anatomy in detail. This allows us to identify the underlying cause of the instability and determine the most appropriate course of treatment.

Most people describe a sudden, visible shift of the kneecap out of place, intense pain, and often the knee buckling or giving way. Swelling typically develops quickly. In many cases the kneecap slips back into place on its own as the knee straightens, though sometimes it needs to be manually repositioned.

Yes. A first dislocation is often treated conservatively, since many people never have another. But once it happens once, the stabilising ligament is stretched or torn, which raises the chance of it happening again — especially if anatomical risk factors are also present. Recurrent instability is approached more proactively, often including a surgical discussion.

Physiotherapy typically emphasises strengthening the quadriceps — especially the inner thigh muscle (VMO) that helps pull the kneecap medially — along with hip and core stability work, since weakness further up the leg can also affect how the kneecap tracks.

Seek care promptly after any kneecap dislocation, even if it slipped back into place on its own — it still needs to be assessed for cartilage damage. Also see a knee specialist if your kneecap frequently feels like it's shifting, catching, or about to "pop out."

Please use the link below to make an enquiry and we will be in touch to book an initial appointment with Mr Barkatali.

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