Mr Tony Smith FRCS ORTH
Specialist Knee Surgery

Telephone: 01978 268050

Patello-Femoral Problems (Knee Cap)

The patella-femoral joint (pfj) is the part of the knee at the front, where the kneecap glides back and forth as the knee moves. Disorders of the pfj are very common and varied in their presentation. Mr Smith has a particular interest in disorders of the pfj and offers a tertiary referral service for patients who are suitable for surgical intervention.

The majority of pfj disorders respond to physiotherapy, this often has to be a period of intensive and prolonged rehabilitation to achieve a good result.

One of the most disabling problems from the pfj is caused by subtle malalignment of the joint. The causes of this are potentially multiple. Initial assessment with a good physiotherapist can rectify a number of these issues using a variety of techniques ranging from simple insoles to patella taping and muscle strengthening. Persistent symptoms thereafter usually require assessment by a knee specialist.

Surgical Interventions

Tilted Patella
Tilted Patella

If a patient has completed a course of rehabilitation and is still experiencing symptoms further assessment by a knee specialist may be helpful. Initial investigations usually include x-rays (including a 'skyline' view) and often an MRI.

Lateral Release
Lateral Release

If the pfj shows signs of 'tilting' on further assessment an arthroscopy and lateral release may be beneficial. This is a keyhole procedure to divide the tight or tethering structures attaching to the outer-side off the knee cap and thereby ease the pressure experienced by the pfj. This procedure is usually perfomed as a daycase but is associated with a small risk of a little bleeding afterwards and requires slightly more prolonged rehabilitation than an arthroscopy for a simple meniscal tear. A lateral release may be supplemented with a chondroplasty as well if the undersurface of the knee cap is damaged.

Patella-Femoral Instability

Up until very recently pfj instability has been incompletely understood. Patients with pfj instability fall into two groups.

  1. Patients who have sustained an injury that has disclocated the knee cap and subsequently then experienced recurrent episodes of full or partial dislocation. Patients in this group are usually in their late teens or twenties. Provided all investigations don't show any underlying abnormality of the pfj such patients do very well with a medial patella-femoral ligament (mpfl) reconstruction.
  2. Patients who have experienced problems with one or both of their knee caps popping out of joint since early teens. Usually a history of injury is not present and a number of patients find the can dislocate their pfjs voluntarily. This is an extremely disabling and distressing condition that can render a patient quite disabled. Treatment of this problem is far more complex and requires careful investigation before a treatment plan is agreed upon. The options include, mpfl reconstruction, tibial tubercle osteotomy, trochleaplasty, derotation osteotomy and lateral release. One or a combination of these procedures may be required to make the pfj stable once again.

Medial Patella-femoral Ligament Reconstruction (MPFL)

Mr Smith has lead the way with mpfl reconstruction in his region, he has utilised a number of techniques, all of which give excellent results. The operation involves moving one of the hamstring tendons from behind the inner aspect of the knee and attaching it to the side of the knee cap. In this position it can act as a 'check rein' and guide the knee cap into the correct position as the knee bends and prevent dislocation.

Tibial Tubercle Osteotomy

The underlying problem can occasionally be one mal-positioning of the tibial tubercle. This is the bony prominence at the top of the shin bone where the patella tendon attaches. Repositioning the tibial tubercle can restore the line pull correctly and prevent further dislocations of the pfj. If the knee cap is high riding (another cause of dislocation) it can be lowered at the same time.

Derotation Osteotomy

Occasionally a complex series of subtle developmental spiral twists can occur as the bones of the lower limb grow. The majority correct naturally with growth but occasionally it fails to do so and may cause pfj dislocations. Correction of the rotational problem requires extensive surgery and can be discussed in detail on the rare occasions it is required.


One of the more recently appreciated causes of pfj dislocation is trochlea dysplasia. This is a developmental problem of the knee. Instead of having a groove down the front of the knee to accommodate the knee cap (like a keel in a groove) the knee may have no groove at all or even a convex trochlea. This results in the knee trying to balance the domed undersurface of the knee cap against a domed trochlea, leading inevitably to dislocation of the pfj. The operation of trochleaplasty involves a large procedure to create a trochlea groove for the knee cap to run in.

Trochlea Dysplasia
Trochlea dysplasia

All of these procedures can be performed in isolation or combination as required, Mr Smith will take each case individually and discuss the options available. The rehabilitation after patella-femoral stabilisation surgery must be tailored to each patient and what type of surgery has been performed. For all patients the principals of early movement and muscle strengthening are adhered to. Most patients are perfectly happy to return to work around 6 weeks after surgery and sporting activity at 10 to 12 weeks.


Gwobrau GIG Cymru Award
Independant Healthcare Awards

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