Weak at the knees?
Every year around 8,000 Australians experience their first patella dislocation, with many going on to suffer repeat dislocations.
Patella (kneecap) instability occurs in several guises: sometimes patients will feel that their knee is unstable, or just feel like the kneecap is not quite sitting right. For many, the first sign of a problem is a complete patella dislocation, where the kneecap shifts substantially — generally to the outer (lateral) side of the leg.
Most commonly, people experience their first dislocation in their teenage years, usually during sport or dancing, with women far more likely to dislocate a patella than men.
According to Epworth orthopaedic surgeon Dr Jonathan Robin, the most common cause of patella instability is abnormal development of the femur groove, known as the trochlear groove.
“Where the patella is meant to move with the end of the femur, most often we will find that the trochlear groove is either flat, or even convex. This is called trochlea dysplasia. When a person experiences multiple dislocations, an MRI is best to see whether there is an issue with the trochlear groove that is causing the dislocations and if we can fix that surgically.”
Surgery involves beveling out the groove and recreating a more natural groove for the patella to move in, then re-fixing the cartilage to stabilise the patella joint. Being open surgery, generally a two-night hospital stay is required, with subsequent recovery time at home.
The next most common cause of patella instability is ‘patella alta’ — or a high-riding kneecap. Here, the kneecap tends to be late in finding the trochlear groove during bending of the knee, causing the patella to dislocate.
Patella alta is corrected through a combination of open and keyhole-assisted surgery, where the surgeon detaches the patella tendon and moves the kneecap towards the foot by up to 8mm, then screws it back into place.
“Many patients will have both trochlea dysplasia and patella alta, which can be addressed with corrective surgery at the same time,” Jonathan says.
When you have experienced a patella dislocation, Jonathan says it is also very common to have damaged or ruined the medial patella femoral ligament (MPFL).
To correct this, surgeons most commonly use a part of the hamstring tendon to replace the damaged ligament, which is known as an MPFL reconstruction. Jonathan says doctors often opt for a reconstruction rather than a direct repair of the native ligament, as trying to get the ligament back to its normal length and tension is difficult — sometimes even impossible — once the patella has dislocated.
The recovery period after knee surgery usually involves six or more sessions of weekly physiotherapy and then a slow return to normal activity. Most people can return to sport or dancing within six months post surgery, depending on the complexity of the procedure. In the most severe cases, a return to sport is sometimes not possible.
Patella instability is a highly correctable problem, says Jonathan, and better to address early through surgery.
“We no longer accept that we have to stop activities altogether following a patella dislocation or repeated dislocations. Whether you are an active sportsperson or a dancer, you don’t want to stop your favourite activity, so most people choose to get it fixed early,” Jonathan says.
Ignoring patella instability can potentially cause problems down the track, adds Jonathan, such as arthritis — which may develop after repeated injuries from dislocations and the altered way in which the patella moves on the trochlea.
“The first port of call if you have previously dislocated your patella is to visit your GP. In an acute setting, a patella can often be relocated by straightening the leg. If you are unable to relocate it, you should go straight to your nearest hospital emergency department for assistance and investigation,” he says.
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