Dislocation of the Patella (knee cap)
The patella is an integral part of the knee function and one’s ability to straighten their leg. Called the extensor mechanism, the quadriceps muscle, the patella and the patella tendon are the system that extends the knee. The patella (knee cap), rides in a groove in the femur (thigh bone). In a dislocation, the patella is forced out of this groove and slides off the side of the femur. It can get stuck out of the groove and occasionally needs anesthesia and someone to put it back (reduce the dislocation). The vast majority of the time, the patella comes out to the outside of the knee (lateral dislocation), but it can also go it to the inside. There are numerous reasons that this can happen including trauma, anatomic variations, muscle imbalance, and others. Most often, a dislocation occurs due to a twisting injury with someone who is predisposed to dislocation to to anatomic variations. There are numberus anatomic variations that make your patella more likely to come out including a high riding patella (patella alta), a shallow groove (trochlear displasia), a high angle of force of the quadriceps (Q-Angle or TT-TG ratio), an insufficient medial ligament (MPFL), etc. A complete evaluation of the knee cap and anatomy will involve a physical exam, xrays and an MRI.
For first time dislocators with relatively normal anatomy, the preferred treatment is bracing and gradual return to sports after completion of a physical therapy program. PT will focus on range of motion and quad strengthening, especially the VMO muscle which is the dynamic medial stabilizer of the patella. A lateral buttress brace or McConnel taping is then employed in sports for a year after the injury.
Surgical treatment is indicated in repeat dislocators, a first time dislocation with significant bony abnormality that makes a second time dislocation very likely, or a first time dislocation with loose bodies in the knee joint. Surgery will involve knee arthroscopy to evaluate and treat the cartilage in the knee and then one or more of many procedures tailored to address the deficiencies that caused the dislocation in the first place. These can include:
- MPFL (medial patella femoral ligament) reconstruction
- MPFL Repair
- Medial Reefing
- Lateral Release
- Tibial Tubercle osteotomy
Recovery and Rehabilitation
Recovery is dependent upon what procedures need to be done. One should expect 6 weeks on crutches with limits to range of motion in the first six weeks. You will then progress to an increase in motion and weight bearing after this initial period. The recovery period is usually 4-6 months before return to competition is expected.
- How long does surgery take? Between 1 and 3 hours
- What kind of anesthesia will I need? General anesthesia with or without a nerve block
- How long will I be in the hospital? Many patients can leave that same day, occasionally Dr. Petre will have you stay one night in the hospital
- Is surgery safe? All surgery has risks; however, this surgery when compared to all other surgery is very safe.
- Will I need physical therapy? Yes. Physical therapy is crucial to an excellent outcome.
- How long before I can return to work/school? For jobs and academics that require minimal physical exertion and can be done with crutches, many people can return in a few days to 2 weeks. For jobs that require heavy lifting or exertion, it is safe to plan 8 weeks off.
- How long before I can return to my sports? Typically 4-6 months
- How long before i can drive a car? All patients must be off pain medicine before driving. Many patients can return to driving in 2 weeks or less once they feel completely safe operating a vehicle.
- How long will I be on crutches? 6 weeks minimum
- How long will I need pain medicine? Most patients need 3-5 days of pain medicine and sometimes up to 2 weeks. If you are still having pain requiring narcotic pain medicine after a month, Dr. Petre may ask you to see a pain specialist.
- How long will I need a brace or sling? 6 weeks