By Dr Philip Dupre - Orthopaedic Surgeon
This condition invariably presents in adolescence and mainly affects girls. The first dislocation usually occurs with a twisting movement while the knee is in slight flexion. Reduction is often spontaneous so diagnosis of what has happened may not be obvious.
There is always tenderness medial to the patella where the capsule has been torn and severe apprehension is demonstrated if the patella is gently pushed laterally while flexing the knee. (Apprehension test).
Following the initial dislocation, recurrence is common, because the medial patello-femoral ligament and capsule have been torn and stretched. Physiotherapy is usually arranged initially in order to strengthen the medial quadriceps muscle. Operative correction is required if the problem becomes recurrent and fails to respond to conservative measures.
The aim of surgery is to tighten the medial capsule and release the lateral. More severe cases may require realignment of the patellar tendon.
An alternative to operative treatment is to contract and strengthen the medial capsule and patello-femoral ligament by injecting a mixture of 50% glucose solution mixed with local anaesthetic in equal parts. This has the effect of causing an inflammatory reaction which contracts and thickens connective tissues.
The technique is to infiltrate 3mls. of this mixture into the medial patello-femoral ligament which lies supero-medial to the patella. Symptomatic improvement is usually noticed about a week later and repeat injections may be necessary at 3 to 4 week intervals which will give successive improvement.
About 3 to 4 injections are usually required over the next few weeks or months to give complete stability and symptomatic relief.
In older patients with patello-femoral pain, the same principle applies if skyline x-rays of the patella show lateral shift or malalignment.
