The most common reason to operate on the patella is for instability and dislocation. If pain is the problem rather than instability, then typically the treatment for this is physiotherapy with surgery only rarely having a role to play.

Once a patellar dislocation has occurred, there is a high chance that it will recur without treatment. Typically physiotherapy is used after a dislocation to strengthen the quadriceps muscles, especially the VMO component, mobilise the patella, correct any tilt of the patella and tighten the supporting structures. Sometimes surgery is necessary after a first time dislocation.

10% of patients will have a fracture and loose body within the knee from the dislocation, which can be removed arthroscopically. Also, if there is an acute tear of the major stabilising ligament of the patella – the medial patellofemoral ligament – then a small operation repairing this ligament, may reduce the chances of further instability.

Typically the patient who will benefit most from this surgery has had a traumatic dislocation with a mild predisposition to patellar instability and an obvious tear of the MPFL which confirmed on MRI scan. Commonly these are patellar dislocations on the sporting field. Although this is a small operation, an arthroscopy plus a 2-3 cm incision over the MPFL on the inside of the knee, recovery typically takes about 3 months. Once the patella has dislocated a number of times, a simple repair of the MPFL will not prevent further episodes, as the ligament itself is now too damaged and stretched to prevent recurrence. An intensive physiotherapy programme becomes mandatory in the recurrent situation.

Surgery for recurrent patellar instability is very difficult and further dislocation is not uncommon. Many operations have been described in literature, which usually means that none of these work well. Recently there has been great interest through ISAKOS (International Society of Arthroscopic Knee & Orthopaedic Sports) in patellar instability. The key to successful surgery is to investigate the knee appropriately with a targeted examination, an x-ray, a CT scan or MRI scan to define the exact problem with the individual patellofemoral joint. From these investigations the appropriate surgery can be targeted.

With some patients a reconstruction of the MPFL may be necessary and other patients may need a distal realignment of the patellar tendon. Some patients may need the lateral soft tissues lengthened. Sometimes a deepening of the trochlear groove where the patella runs in may be the answer. Commonly, it is a combination of all these approaches that is necessary. Importantly, excision of the patella is never the answer for instability

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