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The information: patellofemoral pain syndrome

Professor Fares Haddad, consultant orthopaedic surgeon, and registrar Mr Tony Fayad continue our series of evidence-based lowdowns using PUNs and DENs

 

 

The patient's unmet needs (PUNs)

A 16-year-old girl attends complaining of pain in both knees, especially after exercise, for the last six months or so. She is very sporty and is due to represent her county soon in various track and field events, but her mother is worried the symptoms are putting her participation in jeopardy. Periods of rest ease the symptoms, but they flare up again whenever she resumes sport. On examination there is tenderness on the borders of the patella, but otherwise the knees seem normal. You diagnose patellofemoral pain syndrome. Mother and daughter are keen to know the cause and prognosis and to pursue effective treatments.

 

The doctor's educational needs (DENs)

What is patellofemoral pain syndrome and what is the pathophysiology of the pain?

Patellofemoral pain syndrome is characterised by anterior knee pain involving the patella and retinaculum that excludes other intra-articular and peri-patellar pathology. The pain comes on gradually and symptoms may relate to abnormal contact of the posterior surface of the patella with the femur. Patellofemoral pain syndrome is a broad term that should be used when no other cause can be identified. It is often used interchangeably with ‘anterior knee pain' and ‘theatre-goer's' or ‘cinema knee'.

Patellofemoral pain syndrome is quite common in young people, particularly adolescent girls. It is one of the most common knee problems in female adolescent athletes.1 Patients are more prone to it if they have a small kneecap or one that sticks out if the feet pronate, and if they have tight muscles or weak quadriceps. It also affects athletes who do a lot of long-distance or hill running, and those who have had a previous knee dislocation.

Patellofemoral pain syndrome is often confused with chondromalacia patellae, where there is softening of the patellar articular cartilage. Chondromalacia patellae only occurs in a subset of patients with anterior knee pain – but both conditions can occur in isolation. It is unclear why some patients with minor chondral softening of the patella have severe pain, while others with chondral fissures and defects can manage high-level sport. So chondromalacia patellae is often bracketed with patellofemoral pain syndrome – the precise cause of the pain is unknown and the management of both conditions is similar.

 

How often is patellofemoral knee pain the result of another issue, such as joint hypermobility or flat feet? Should we look for underlying causes like this?

Patellofemoral knee pain is usually secondary to maltracking, where a muscle imbalance develops when any of the structures surrounding the knee, which keep the patella sitting centrally in the intercondylar groove, are particularly tight or weak. This causes pain and can lead to patella cartilage damage. The patella most commonly runs too laterally in the groove.

All patients should be examined to rule out biomechanical problems. Patients initially should be examined ‘from the ground up' while standing in shorts. Assess dynamic patellar tracking by having the patient perform a single leg squat, and then stand with the hip, knee and ankle in a straight line. This is a great test of patella control – for many patients, the problem is muscle weakness, particularly in the glutei and core. Observing the patient's gait may reveal excessive subtalar pronation, which can be a cause of imbalance leading to knee pain. Imbalance between the medial and lateral patellar forces, caused by vastus medialis obliquus dysfunction or lateral structure tightness, can manifest as an abrupt medial deviation of the patella as it engages the trochlea early in flexion, known as the ‘J' sign. Lateral deviation of the patella can be seen during the terminal phase of extension.

Foot abnormalities are thought to be a cause of patellofemoral knee pain. Patients with patellofemoral knee pain often have a higher arched foot (cavus), which may produce greater pressures on the patellofemoral joint during running. Genu varum, genu valgum and foot postural abnormalities – excessive pronation, valgus ankles and lowered foot arches – might also increase risk of injuries.2 Evidence suggests generalised ligamentous laxity increases the total patellar mobility, which alters patellar tracking and causes symptoms. One study found significant generalised ligamentous laxity in patients with chondromalacie patellae.3 Other structural problems include patella alta (a high patella) and patella baja (a low patella).

 

What is the outlook for a patient with patellofemoral pain syndrome? Is there any evidence they are at increased risk of subsequent arthritis?

If a relationship between patellofemoral pain syndrome and patellofemoral osteoarthritis can be identified, clinical interventions that address the former could potentially delay progression of the latter. But investigation into the causative link between the two is limited. A recent analysis looking at six small, uncontrolled, observational follow-up studies was unable to confirm a link.

Investigations are designed to find problems such as maltracking, osteochondral lesions and excessive lateral pressure syndrome, all of which warrant intervention. In excessive lateral pressure syndrome, early intervention may reduce the risk of long-term chondral damage.

 

What simple activities and exercises can be advised to alleviate the problem? What specific treatments would a physiotherapist use and how effective are they?

Treatment with continuous physical rehabilitation programmes, in combination with NSAIDs, is a highly effective non-operative option. Results have shown a high success rate in decreasing the severity of symptoms.4 Ice, resting, taping the knee and appropriate footwear are also useful.

Rehabilitation exercises can restore patellofemoral joint homeostasis, although the anatomical malalignment may not be corrected. The shape and size of the patella and trochlear groove are limiting factors in the outcome of rehabilitation. The aim of exercise is to build muscle, improve tracking and enhance control without causing pain, which is where the skill of the physiotherapy and rehabilitation team is needed. Quadriceps strengthening is most commonly recommended as the quadriceps play a large role in patellar movement. Gluteal control is key and hip, hamstring, calf and iliotibial band stretching may also be important. 

 

What surgical options are available?

Surgery for patellofemoral pain syndrome is a last resort and should only be considered if a precise anatomical problem is identified that can be addressed. Moreover, surgery alone is never enough – it must be followed by appropriate physiotherapy. Patellar chondral defects may be improved by an arthroscopic surgical procedure to smooth out the surface of the patella or trochlea.

If the problem is clearly caused by excessive lateral tracking secondary to patellar tilt but without patellar subluxation, a lateral release is sometimes appropriate. But other options and treatments should be considered before this. For example, consider whether the lateral tracking could simply be due to a tight iliotibial band or weak quadriceps muscles. Taping the knee to enhance medial glide should be tried. Having the patient wear a quality running shoe or arch support is another measure to try before surgery is contemplated.

 

Key points

Cause

  • The aetiology of patellofemoral pain syndrome is thought to include abnormal forces or prolonged repetitive compressive or shearing forces on the patellofemoral joint.

Epidemiology

  • Patellofemoral pain syndrome accounts for 25% of knee injuries in sports medicine clinics.
  • It is approximately twice as common in women than men.

Clinical features

  • Anterior knee pain is the most common presentation of patellofemoral syndrome.
  • Symptoms often occur during the activity, or may occur later after the activity has been completed, sometimes as late as the next day.

Management

  • Physical therapy
  • Relative rest
  • Ice and NSAIDs
  • Knee sleeves and braces, and knee taping
  • Footwear and arch support
  • Review with a sports physician before surgery is considered
  • Surgery.

 

Professor Fares Haddad is a consultant orthopaedic surgeon and Mr Tony Fayad is a trauma and orthopaedics registrar at University College London Hospital

 

References

1 Ireland M, Willson J, Ballantyne B et al. Hip strength in females with and without patellofemoral pain. J Orthop Sports Phys Ther 2003;33:671-6

2 Waryasz G and McDermott A. Patellofemoral pain syndrome: a systematic review of anatomy and potential risk factors. Dyn Med 2008;7:9

3 Al-Rawi Z and Nessan A. Joint hypermobility in patients with chondromalacia patellae. Br J Rheumatol 1997;36:1324-7

4 Kannus P, Natri A, Paakkala T and Jarvinen M. An outcome study of chronic patellofemoral pain syndrome. Seven-year follow-up of patients in a randomised, controlled trial. J Bone Joint Surg Am 1999;81:355-63 

 

 

More online

Go to pulsetoday.co.uk/gp-videos to watch a video of an exercise programme for anterior knee pain

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