Patella instability and dislocation

Some patients can have problems with their patellofemoral joint, or their kneecap.  One of the most common problems is dislocation, or instability of the knee cap, where the knee cap slides in and out of place, causing pain, and making walking and running difficult.

Some patients dislocate their knee cap after a serious injury, such as hitting the boards at hockey.  In this instance, it is important to get an MRI to ensure that there is no damage to the cartilage or bone that might require urgent surgery.  If not, after an appropriate period of rehabilitation, this problem usually resolves, and ongoing instability is not a problem.

Some patients, usually young women, have unstable kneecaps, without a history of injury.  This is because of some anatomical differences, such as rotational problems at the hip or ankle, having very loose tissue, and being knock-kneed to name just a few.  While at least a year of physiotherapy and muscle strengthening is recommended, if this kneecap instability continues it can be extremely debilitating.

There are two main surgeries that can help.  The first is a ligament reconstruction, which is to make a new Medial Patello Femoral Ligament (MPFL).  Performed through three one-inch incisions using a hamstring tendon, in the majority of patients this is sufficient to significantly improve the function of the knee.  Patients have to be be on crutches for 6 weeks, and rehab for 6 months – it is extremely important to restore range of motion in the first 6 weeks.

More rarely, patients have extremely unstable patellas, which are practically always significantly subluxed or dislocated – this is clearly identified on a MRI.  In this setting, as well as a MPFL reconstruction, patients need to have their knee cap moved over, an operation called a tibial tuberosity transfer (TTT).  While the rehabilitation is the same as an isolated MPFL reconstruction, TTT is a significant operation with increased risk.

Postoperative rehabilitation

Patello-femoral surgery is performed as day surgery at Women’s College Hospital. Someone must come and pick you up and take you home. It is advised to have someone around to help you for the first two days. All patients will be provided with a script for medications that should be filled at the hospital prior to going home. Medications will usually be Celebrex in the morning for 2 weeks, Aspirin at night for two weeks, and Tylenol regularly for the first week. A script for Oxycodone will also be provided.

Patients must use crutches for six weeks. A brace is used to sleep and walk for the first six weeks, and is removed after 2 days to begin bending the knee, when sitting in a chair. Bending will be limited to 90 degrees for the first 6 weeks.

If possible, patients should rent a Gameready machine, which provides ice and compression to the knee, significantly reducing postoperative pain. The information for the rental company will be provided to you.

Physiotherapy is required twice a week, immediately after surgery.  A physiotherapy referral and protocol will be provided for you on the day of surgery. Patients are seen in clinic two weeks after surgery, for wound review. 

Patients should take a week off work after the surgery, and then work from home for another 2 weeks if possible. Patients are not allowed to play sport for 9 months after surgery, as it takes this period of time for full quadriceps strength to be restored.

Risks of surgery

MPFL reconstruction is a relatively safe operation. There is a 1/1000 risk of deep infection, major stiffness, DVT/PE, major nerve or blood vessel damage, and patella fracture. Patients can get local areas of numbness around the graft harvest incisions, which typically improves over a year or two. The risk of retear of the graft over your lifetime is 5%.  The chance of a good outcome / stable knee is 95%.

Tibial tuberosity osteotomy is a bigger operation. There is a 1/100 risk of deep infection, major stiffness, DVT/PE, major nerve or blood vessel damage, and patella fracture.  There is a risk that you can fall, and fracture the leg, which may require further surgery.  There is a risk of non union, malunion, or screw fracture.