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The waiting game

Hip and knee surgery: Patellofemoral arthroplasty a new option for arthritis

Mr Fares Haddad and Mr Reza Jenabzadeh consider a new procedure that can help certain patients suffering from patellofemoral arthritis

Mr Fares Haddad and Mr Reza Jenabzadeh consider a new procedure that can help certain patients suffering from patellofemoral arthritis

Case history

A 52-year-old woman presents with right-sided anterior knee pain. She describes it as being a longstanding aching pain localised just under the kneecap. She cannot remember any trauma to the knee but has always had 'weak knees' and occasional aching. The pain is exacerbated by certain activities such as stair climbing or rising from a seated position. She says squatting exacerbates the pain, as does sitting with her knees bent for a long period, such as during a car journey or a visit to the cinema. She has no previous history of patellar subluxation, dislocation or fracture.

Diagnosis and management

Knee pain from the patellofemoral joint is common. Approximately 5 per cent of patients with osteoarthritis of the knee have symptomatic patellofemoral arthritis in the absence of tibiofemoral arthritis.

Risk factors for patellofemoral arthritis are increasing age, obesity, overuse, chronic joint instability, prior intra-articular fractures, and ongoing patellofemoral maltracking such as the lateral pressure syndrome. Patellofemoral arthritis can also occur in younger patients as a result of malalignment or trauma.Differential diagnoses include:

  • Patellofemoral arthritis
  • Patellar instability
  • Patellar chondral defects
  • Patellar tendonitis
  • Medial plica syndrome
  • Meniscal tear

After a careful clinical history and examination, investigations must include weight-bearing antero-posterior (pictured above right) and lateral views of the tibiofemoral joint and 'skyline' tangential views at 30-45° flexion. These X-rays are examined closely for joint-space narrowing, osteophytes, subchondral cysts/sclerosis, patella alignment and height. Congruence of the patella and patella tilt are assessed on the axial view.

On examination, this patient walked with a normal gait. The knee was not very swollen but a small effusion could be detected. She had a very good range of movement but there was a very loud patellofemoral crepitus. There was no joint line pain, meniscal tests were negative and there was no ligamentous laxity.

Pain was elicited by the patellar compression test (patella compressed as she flexed her knee) and also on resisted knee extension. Her patella also maltracked laterally in flexion. There were similar findings on the left side but with less pain. Full examination of her back, hips and ankles was otherwise unremarkable.

Treatment options

All patients usually undergo a full course of non-operative management before any invasive procedures. Non-operative options include:

  • weight loss
  • NSAIDs and paracetamol
  • activity modification to avoid prolonged flexion
  • muscle-strengthening exercises, specifically for the quadriceps muscle group
  • patellofemoral braces
  • taping the patella into a more medial position ­ advocated by some, especially in young patients undergoing rehabilitation for anterior knee pain
  • MRI scanning, to assess joint surface damage and associated pathology in the tibiofemoral joint ­ rarely alters the management of patellofemoral arthritis

Operative options when non-operative options have failed, include:

  • arthroscopic debridement +/- lateral retinacular release
  • tibial tubercle 'unloading' procedures
  • osteochondral transplantation
  • patellectomy
  • patellofemoral arthroplasty

Summing up

Patellofemoral resurfacing with modern implants produces good functional results at five years, with a low incidence of problems. Ongoing review of implants to date will help to establish the longevity of these prostheses.

As confidence in the results increases, the indications for this procedure are likely to be extended to younger patients with significant damage to the patellofemoral joint.

The procedure

  • patients with isolated patellofemoral osteoarthritis
  • failure to respond to full six-month programme of non-operative measures listed in main text
  • patients with severe functional limitations· patients willing to modify their activity levels
  • patellofemoral arthroplasty is contraindicated if there is tibiofemoral arthritis· patients with patellar maltracking or malalignment

Reza Jenabzadeh is a specialist registrar in Northwick Park Hospital, north-west LondonCompeting interests None declaredFares Haddad is consultant orthopaedic surgeon specialising in knee and hip arthroscopy reconstruction, joint replacement and revision ­ he is clinical director at University College London Hospitals. Competing interests: None declared

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