patellar instability

Managing patellar instability

The American Orthopaedic Society for Sports Medicine has just concluded its annual meeting in Toronto and one research project stood out among the rest, suggesting that younger patients who suffer patellar dislocations are at a higher risk of recurring dislocations, especially in the long term.

The research project, which was conducted by The Mayo Clinic in Rochester, Minnesota, won the Herodicus Award for the best resident paper featured at the meeting, examined a study group of 232 patients who were deemed as ‘skeletally immature’ at the time they suffered ipsilateral recurrent patellar dislocation (in other words, their proximal tibia and distal femoral physes were open at the time of dislocation), who had suffered their injury between 1990 and 2010.

The study concluded that over 20% of those recurrent cases happened in the first two years after the initial injury, and by the 15 and 20-year mark, cases of reoccurrence had shot up to 54% of the study group patients.

Patellar instability: the facts

When we talk of ‘patellar instability’, we’re essentially referring to a welter of conditions which affect movement of the patella or knee cap, including patellar dislocation and patellar subluxation. The patella is a very important part of the knee joint: it forms part of the extensor mechanism, a chain of structures that give the knee the ability to straighten. The patella rests in a groove at the lower end of the femur called the trochlear groove, or trochlea, which centres it during knee flexion and extension, with ligaments on either side of the patella adding further support in keeping it central.

Patellar instability can happen at any time, and complete dislocation of the patella causes sudden, intense pain in the front and side of the knee and a sensation of the knee giving way or popping out. There may be a visible deformity of the knee, due to the patella moving out of position, accompanied with a rapid onset of swelling within the first couple of hours after injury.

Some sufferers of patella dislocation can experience a reoccurrence, where patella moves out of position rather more easily, but it can return to its original position with certain knee movements, usually involving straightening the knee. When this happens, pain and swelling may occur, albeit on a minor basis.

Clicking, crunching, popping and locking

Obviously, for professional athletes and dedicated amateurs, patella dislocation can seriously impact a sporting career, with an ongoing discomfort that may increase on activity, and reoccurrence of pain during knee flexion activities including hill work, squatting or lunging (and going up and down stairs, or course). There can often be tenderness on the lateral side of the patella, as well as clicking or crunching within the joint during flexion and extension, due to articular damage sustained during the dislocation. And of course, the fear of the knee giving way at any point can weigh heavily on your mind.

The study adds weight to previous research, which typically shows that 40% of adolescent patients go on to experience a recurring patellar dislocation. However, the news was not all bad. “Despite high numbers of recurrence, our research showed that these young patients did not develop significant patellofemoral arthritis,” said Thomas L. Sanders, MD, corresponding author of the study. “We hope to use our research to help educate both physicians and parents on the risks young athletes face after these injuries in their early years, and hopefully take steps to prevent them.”

Does patella instability require surgery?

Patella instability typically requires physiotherapy to strengthen the supporting structures of the knee. If there has been damage to the patello-femoral ligament or if the patella is failing to align properly, then surgical repair to the ligament may be an effective option. In severe or recurrent cases, a partial knee replacement may be the preferred option. London knee specialist Mr Jonathan Webb will discuss your options in full during your consultation.