The patellofemoral joint is quite a complex joint. It has bony and soft tissue elements which combine to allow the kneecap to move in it’s groove on the femur as the knee bends and straightens.
The most common problems with the kneecap include arthritis, instability and anterior knee pain.
The patella can be too tight or too loose. In most cases it will be too tight laterally (on the outer side of the knee) which can lead to dislocation of the patella laterally. Much less commonly the patella will dislocate medially. In some case the bony architecture of the joint is normal but an injury allows the patella to dislocate and tears the MPFL (Medial PatelloFemoral Ligament). These patients require a repair or reconstruction of the torn ligamant to restore stability to the patella.
The most common reason for needing a lateral release is the presence of tight tissues on the outer side of the patella with either pain or instability symptoms. The release is almost always performed arthroscopically unless other realignment procedures are also being done to the knee. This puts the knee cap more centrally in the trochlear groove and allows it to track (move) where it should.
The lateral release involves cutting the internal capsule of the joint and can therefore result in local bleeding. There is usually a permanent bulge on the outer side of the front of the knee and often significant bruising for many weeks after the operation (despite the fact that it has been performed arthroscopically (keyhole).
Patellofemoral arthritis (kneecap OA) is very difficult to treat and while many things have been tried to fix it, very few of them work reliably and well. Patellofemoral replacements are still relatively experimental and if they fail mean a much bigger operation with inferior results when changing to a total knee replacement
Anterior knee pain is almost always from tight hamstrings and rarely requires surgery.