PFJ Dislocation / Subluxation


  • The patella moves either partially (subluxation) or completely (dislocation) out of the trochlear groove of the femur where it usually resides
  • Lateral PFJ dislocations are most common due to the same factors that trigger patellofemoral joint pain
  • Medial PFJ dislocations are possible from direct violence (blow to lateral patella) or overzealous operative correction (eg tibial tubercle realignment or medial patellofemoral ligament reconstruction)
  • With lateral PFJ dislocations:
    • Most of the time, there is a small associated fracture, which is most commonly an avulsion fracture of the medial side of the patella (which is often not evident on plain x-ray and only on MRI). These are usually of clinical insignificance
    • Most of the time, there is disruption to the medial retinaculum +/- the medial patellofemoral ligament
    • There will be chondral bruising of the patellofemoral joint
    • There may well be a haemarthrosis


  • The patient will usually report that the patella either felt like, or was visualised to come out of place (+/- return back into place)
  • Don’t assume that there was not a PFJ dislocation simply because it was not visualised by the clinician
  • Commonly there is a haemarthrosis
  • There will be pain around the patellofemoral joint, particularly medially (medial retinaculum)
  • There is usually increased pain on increased knee flexion (more patellofemoral compressive force from the stretching of the quadriceps)
  • The apprehension test will usually be positive (see knee tests)
  • Ensure that the patient can straight leg raise


  • If the patella remains dislocated, it can usually be easily reduced by straightening the knee passively +/- gentle medially directed force to the patella
  • Due to the damage to the medial structures and articular cartilage, it is advisable to immobilise the knee in a knee extension (Zimmer) splint to keep those structures in a shortened / less compressed position until they have healed adequately. The author has found that this usually occurs in about 2 weeks (judged by pain reduction and absence of positive apprehension testing), but may take longer in some individuals. There has been little research into the optimal period of immobilisation.

  • After this period of immobilisation, a program of rehabilitation supervised by a physiotherapist should be completed similar to that for patellofemoral pain
  • Generally speaking, sport should be avoided for a period of at least 6 weeks, after a graduated return to sport program
  • Recurrent (3 or more) dislocations should be referred for Orthopaedic review. Surgical management consists of relatively drastic measures, such as removing the tibial tubercle and reattaching it more medially (to provide more mechanical support as the line of pull of quadriceps will naturally want to pull the patella superiorly and slightly laterally; patients with a greater Q angle are therefore more susceptible to dislocation, and medial translation of the tibial tubercle will reduce the Q angle) or reconstructing the medial patellofemoral ligament (often using the hamstrings looped through a corner made in the medial corner of the patella). Conservative management should, therefore, be thoroughly exhausted before operative management considered.