Patella (knee cap) problems

Figure 1. (1) If there is tightness in the outside of the knee a lateral release of the muscles is done. (2) If there is poor development of the patella in its groove on the femur a muscle advancement on the inner thigh is performed. (3) If there is high pressure on the knee cap the patella is elevated by raising the tibial tubercle. (4) If there is a tendency for the patella to flop off the femur on the outside the tibial tubercle is pushed inwards. If however all structures mentioned in 1-4 are normal, then an MPFL ligament reconstruction alone is considered (5).

Figure 2. A common condition related to altered patello-femoral mechanics is recurrent habitual patella dislocation. This is predisposed to by a number of anatomical abnormalities. The patient is often knock-kneed (valgus, a). This results in a patella that falls off to the outside of the knee (arrowed). Sometimes the patella tendon is too long (dotted line in c) compared to the normal side (b) if the condition isn't bilateral. These imbalances do not allow the knee cap (patella) to sit in its groove and it falls off to the outside (d). With all these abnormalities in place the joint capsule adjoining the patella (the medial retinaculum) can get torn (arrowed in e) allowing the patella to dislocate.

Figure 3. Treating the habitually dislocating patella requires a consideration of all forces acting on it as outlined in Figure 1. In this particular case the medial patello-femoral ligament was reconstructed with an allograft sling (a). The insertion of the patella ligament was then pushed inwards and secured with two screws (curved arrow in b). Compared with Figure 2 it should be apparent how the patella now appears to be in a more normal position (straight arrow). Under anesthesia these changes can be monitored closely where a dislocated patella (c) is gradually moved into its normal position (d).

Figure 4. The patient had tightness on the outside (a), with a tilt and arthritis had begun (b). A lateral release and tibial tubercle elevation and medialization using a bone block spacer was performed. Six months later, the patello-femoral joint was re-established (c), the patello-femoral joint was more aligned and the bone block had incorporated well (d).