Patella dislocation is when the knee cap is moved completely out of joint. In most people this will occur following a significant injury. Often the patient cannot reduce or put back the knee cap themselves and will have to be taken to hospital to have this done. A period of rest followed by physiotherapy is often enough to get the patient back to normal function within a few weeks. However once a patella dislocation has occurred, the patient is then at risk of what is referred to as recurrent dislocation. The second time this happens often does not require as much force. This is because some of the restraining structures that normally keep the knee cap in place are damaged at the time of the first dislocation.
The younger a patient it is, the more likely they are to get recurrent dislocation. Also the younger a patient is, the more likely they are to have inbuilt anatomical variants that put them at risk of patella dislocation. It is in this latter group where surgery may be indicated to prevent the dislocation from repeatedly happening.
One of the consequences of a dislocation is that the muscles around the knee will waste and this will tend to aggravate to make the problem worse and increase the risk of further dislocation.
First line treatment is usually to see a physiotherapist and start building up the muscles. This will protect the knee and even if not fully successful in preventing repeated episodes of dislocation, can put the knee in a better position to undergo surgery
Patients who suffer repeated dislocations or who grow to lose trust in the knee will often require some form surgical stabilisation. The decision to proceed to surgery really depends on the number of times the knee cap has come out and the interval between occurrences. Frequent rate of dislocation will disrupt the patient's life and surgery can be very beneficial proving that situation.
Acute surgical intervention for patella dislocation after the first event is regaining interest. Direct repair of the damage tissues and early rehabilitation has been shown in certain circumstances to improve the long term outcome and get the patient back to normal living quicker. There is a disadvantage in having a further surgical procedure after a traumatic one but in the higher risk groups surgery may be a better option than suffering multiple further dislocations before intervening.
Older patients who suffer their first her dislocation however have a much reduced rate of recurrent dislocation and physiotherapy and rehabilitation would be the treatment of choice.
If surgery is contemplated, the patient's anatomy needs to be thoroughly investigated usually with an MR or CT scan to determine the exact pathology. As many of these patients have some inbuilt tendency towards dislocation, that needs to be taken account of when planning surgery.
The mainstay of patella stabilisation involves releasing the tight lateral side of the patella strengthening up the inner medial side of the patella and altering the point of attachment of the patella tendon so that muscular contraction and movement of the patella pushes it more into its normal midline position and to the outside. All these procdures require dedicated physiotherapy and rehabilitation to get the most out of them