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Patellar Luxation

The patella (“kneecap”) is a small bone embedded within the high muscles, and it acts as a fulcrum allowing us (and our pets) to extend their knee. Where it contacts the femur (thigh bone), there is has a smooth cartilage covered groove to permit smooth gliding. In some instances, the patella will luxate (“dislocate”) from the groove, thereby wearing away its smooth cartilage undersurface and disrupting the normal function of the knee joint.

Surgery to correct a patellar luxation may involve a few different components, depending on your pet’s specific conformation:

 

  1. The portion of the tibia that the patellar tendon (that tendon on the front of your knee) attaches to may need to be moved over, so that the patella is realigned with its groove. This is done by making a partial cut in the tibia, moving it opposite the direction of luxation, then stabilizing it with metal pins (see below X-rays).

  2. The groove that the patella glides in may need to be reconstructed so that it is deeper. To perform this, the groove is cut so that it may be lifted up, allowing us to remove some bone underneath. Then the groove is replaced and we now have a deeper groove, that has maintained a smooth cartilage gliding surface, giving the patella a cozier fit.

  3. The patella, and the entire knee joint, is surrounded by a very touch joint capsule. When our pets patella has been popping in and out of the groove for a period of time, the joint capsule towards the side of luxation begins to contract, while the joint capsule opposite the side of luxation becomes very loose. Therefore, it is very common to imbricate (‘tighten up”) the joint capsule on the one side, while releasing (“loosening”) the other side.

Unique components of this surgery:

  • Jumping (yes, including furniture) and stairs are EXTREMELY discouraged until Dr. Lynch gives you the clearance to do so. These actions are very high risk for re-luxating the patella (popping the kneecap back out) during the recovery period.

These are side view X-rays of a dog’s knee BEFORE (left image) and AFTER (right image) their patellar luxation correction surgery.

 

  • The patella (kneecap) is circled in red

  • The thigh muscles and patellar tendon (red lines) represent the mechanism that extends  the knee joint, using the patella as a fulcrum as is glides within its groove (green lines)

  • The portion of the tibia (shin bone) that the patellar tendon attaches to is shown as the blue asterisk.

  • This patient had a MEDIAL patellar luxation, causing the kneecap to dislocate to an abnormal position, inside relative to its groove.

image (43).png

These are side view X-rays of a dog’s knee BEFORE (left image) and AFTER (right image) their patellar luxation correction surgery.

 

  • The patella (kneecap) is circled in red, with the thigh muscles and patellar tendon (red lines) inserted on the top of the tibia

  • The green asterisk on the BEFORE image represents the position that the patella should be, atop/within its groove

  • Note the two metal pins utilized to secure the portion of the tibia in position

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