The Patellofemoral Joint. Incongruence, Instability and Arthritis

  • Damian Clark

Student thesis: Doctoral ThesisDoctor of Medicine (MD)


The relationship between patellofemoral joint (PFJ) instability and arthritis is little explored. The PFJ cartilage transmits more force per area than any other joint cartilage. The unstable joint may have a different pattern of congruence to the stable joint.

A case-controlled study without matching was performed, amongst the co-variables included were demographic and anatomic risk factors for patellofemoral instability. In the final analysis, there were 73 patients in the patellofemoral arthritis arm and 87 patients in the medial unicompartmental arthritis arm. The co-variables of female sex, patella alta and early onset of
symptoms increased the odds of developing patellofemoral arthritis over medial
compartmental arthritis.

The results of the first study stimulated a second study. This study sought to
characterise the congruence of the patellofemoral joint during activity, to better understand if the surface area available for force transmission differed in cases of instability. An imaging study of eighteen patients with a history of PFJ instability was performed, this study evaluated the congruence of the PFJ throughout flexion. The study found that the unstable PFJ is less
congruent than the normal PFJ throughout knee range. Stabalising the joint (by various surgical procedures) had the unintended consequence of restoring joint congruence.

In the final study a dynamic evaluation of 13 ambulant patient was performed. The gait of people with patellar instability and those with normal knees were compared by inverse dynamics analysis. Comparison included kinematic, morphometric and force data in a linkedsegment model and is used to evaluate limb joint angular excursions, net joint moments and net joint powers. The gait cycle of some of the patellar instability patients was characterised by quadriceps inhibition gait where the patient failed to generate an extensor moment during
weight-bearing. In eight of the patients the preoperative data was compared to data collected one year after surgery. Restoration of normal gait was noted.

An association between instability and arthritis is supported by these studies. The precise pathway between instability and arthritis remains unknown. Patients with PFJ instability experience dislocations that may cause cartilage damage. They also have abnormal joint anatomy, biomechanics and gait. In addition to traumatic dislocations; excessive loading of cartilage due to abnormalities of joint anatomy and incongruence may lead to accumulated damage and arthritis.
Date of Award6 Nov 2018
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorDomingo J Tortonese (Supervisor) & Michael R Whitehouse (Supervisor)

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