Patellofemoral Joint Replacement
Patellofemoral Joint Replacement
What is Patellofemoral joint replacement?
  • Patellofemoral joint replacement (arthroplasty) is a type of partial knee replacement used to replace the worn out (arthritic) patellofemoral compartment of the knee i.e. the patella (knee cap) and the femoral groove (trochlea) that it glides on as the knee bends and straightens out
  • The patella is replaced with plastic and the corresponding surface on the femur called the trochlea is replaced with metal
  • The remaining joint surfaces of the medial (inner) and lateral (outer) compartments of the knee as well as the ligaments are all preserved
  • This is ideally suited for patients with isolated patellofemoral osteoarthritis
  • Patients are often younger than those with more widespread arthritis and it helps buy time and provide pain relief until the arthritis in the knee spreads to the other compartments
  • When and if this happens then it’s a relatively simple procedure to revise it to a total knee replacement
Risk Factors for patellofemoral osteoarthritis:
  • Obesity
  • Patella fracture
  • Females
  • Patella instability
  • Malalignment of the leg
  • Abnormally shaped trochlea from birth (the part of the femur that the patella glides on)
  • Muscle strength imbalance and tightness in lower limb

Indications: when is it suitable?
  • Patients present with:
    • pain at the front of their knee 
    • Pain that is aggravated:
      • when going up or down stairs (going down is typically worse)
      • rising from a seated position
      • squatting
      • kneeling
      • sitting for prolonged time with knees bent (e.g. driving or watching a movie)
    • Pain is less severe when:
      • Walking on level surface
      • Standing with knees straight
    • Stiffness
    • Crunching and grinding sensation when going up and down stairs
Contraindications: When is it not suitable?
  • Presence of arthritis in the other part of the knee i.e. between the tibia and femur 
  • Presence of excessive malalignment of the knee
Investigations
  • X-rays:
    • AP (frontal view): helps confirm that the inner and outer knee compartments are not affected by marked arthritis
    • Lateral (side view): assess degree of wear in patellofemoral compartment
    • Skyline view: helps show degree of wear between patella and femur
  • MRI scan:
    • Can accurately show location and degree of wear in patellofemoral compartment 

Advantages of Patellofemoral Joint Replacement vs Total Knee Replacement
  • More natural feel and movement:
    • Due to preservation of the remaining part of the knee and the ligaments
  • Functional and activity scores are superior
  • The wound is smaller
  • Less painful
  • Quicker recovery
  • Quicker return to work and activities
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