The patella (knee cap) doesn’t sit in the centre of the groove on the lower femur. This is because three structures are not in a straight line:
1.Bone at the front of the tibia
2.The groove in the lower femur
3.The muscles and tendons pulling on the patella
When the patella is out of the groove, the groove becomes shallower, or the ridge may be worn away, making the problem worse.
Causes include genetic factors, trauma or ligament problems but often cannot be tracked down precisely in any one dog. Many dogs may have a combination of several causes.
The patella rubs on the edge of the ridge or the rough bone to the side of the ridge. This wears away the cartilage, eventually causing pain and arthritis.
1.Realign bone at front of tibia to match the muscle and femur (“tibial tuberosity transposition”).
2.Deepen groove of femur (“sulcoplasty”)
3.Loosen soft tissue on tight side (“release”)
4.Tighten soft tissue on loose side (“imbrication”)