Patellar dislocation is one of the most common knee injuries.

Patellar dislocation can cause extensive cartilage damage in the patellofemoral joint.

For habitual dislocations, surgery can restore patellar stability.

Symptoms

  • pain
  • swelling
  • an audible crack in the knee
  • an abnormal knee outline due to displacement of the kneecap, if it does not return spontaneously to its normal position
  • restricted movement due to pain and bleeding into the knee

Diagnostics

  • diagnosis is based on a thorough medical history and orthopaedic examination. The kneecap quite often returns spontaneously to its normal position after injury.

conventional X-rays and ultrasound are useful additional examinations

  • for recurrent or habitual dislocations, diagnostic assessment should include a long-leg X-ray and often MRI

Treatment

  • a first traumatic patellar dislocation usually requires reduction if it has not occurred spontaneously at the injury site, aspiration of blood from the joint, and immobilisation in a brace for approximately three weeks
  • recurrent dislocations usually require arthroscopic surgery to balance the forces acting on the kneecap during movement. Depending on the damage, this may involve retinaculotomy, cutting one of the patellar supporting bands, or reconstruction of the damaged medial patellofemoral ligament (MPFL).
  • habitual dislocations usually require surgery involving reconstruction of the patellar supporting bands, transfer of the tibial tuberosity, where the patellar tendon attaches, or corrective osteotomies, cutting and refixing bone in a limb with abnormal alignment

Postoperative management

  • in most cases, patients can leave hospital on the second or third day after arthroscopic treatment of recurrent patellar dislocations
  • patients usually use forearm crutches for four to six weeks to protect the operated knee
  • the operated limb is supported by a knee brace for approximately three to six weeks