A patellar dislocation refers to when the patella- the kneecap- moves out of its normal groove in the front of the knee and slides to one side. A subluxation- or a partial dislocation- occurs when the patella partially slides out of its normal groove and slides back in on its own. Patellar dislocations most often happen laterally, or toward the outside of the knee/body, but it is possible for them to also dislocate medially, or toward the midline of the body.
Symptoms
Extreme pain
Rapid swelling
Obvious deformity
Pain particularly on the medial- or inside toward the midline- aspect of the knee
Instability
Apprehension to move or loss of movement of the knee
Feeling like the patella is “out”
Hearing or feeling a loud “pop”
Causes
Contact with another person or an object
Non-contact injury when foot is planted and there is a rapid change of direction or twist
Direct blow to the knee
Shallow groove or uneven groove that the patella sits in
Weak or unbalanced muscles of the quadriceps
Risk Factors
Young women with undeveloped muscles
Ligamentous laxity
Cerebral palsy
Down syndrome
Tight illiotibial (IT) band
Muscle imbalance
Prevention
Training for muscle balance
Quadricep strengthening
Bracing or taping
Diagnosis
Physician will check range of motion and inquire about mechanism of injury
X-ray to check for fracture
MRI to assess ligamentous and soft tissue damage
Physician will assess groove that patella normally sits in
Treatment Options
Non-surgical:
Reduction of dislocation (self or manual)
Immobilization for 7-10 days followed by slow gradual mobilization
Non weight-bearing on crutches for 3-4 weeks
Physical therapy for hip and thigh strengthening
Non-steroidal anti-inflammatory drugs for pain and inflammation
Full recovery in 3-6 weeks if there is no ligament or other soft tissue damage
Surgical:
Arthroscopic repair of medial patellofemoral ligament if torn or damaged
Lateral release surgery to decrease lateral tension and tighten the medial side