Kneecap Arthritis
If arthritis already exists under the kneecap or in the underlying trochlear groove, pain can still persist even if the kneecap is in the correct position.

If this is the case, the surgeon can move the kneecap up, down, left, or right in such a way as to take pressure off the raw area(s). This is only an option if most of the cartilage is intact. Other alternatives include:

• Creating small holes in the raw surface of the kneecap to bring cartilage-producing marrow to the surface (the microfracture technique)
• Taking cartilage plugs from a different part of the knee to replace the worn area (similar to the hair plug technique)
• Harvesting a small amount of cartilage from another part of the knee, which is then cultured and grown in a laboratory for an ultimate reintroduction to the knee.

The worn undersurface of the kneecap can be replaced with a plastic implant. This implant can be a round button less than one inch across, or it can cover the entire undersurface of the kneecap. The groove with which the kneecap articulates can simultaneously be covered with a fine, metallic shield (during an implant called Patellofemoral Replacement), which is a form of partial knee replacement.

Side view x-ray of a patellofemoral replacement 

There are a host of different options available for patients suffering from arthritis, including:

• Minimally Invasive and Moderately Invasive Surgery: Though the incisions used for knee replacement surgery are far smaller than they used to be, they are still big enough to allow the surgeon comfortable access to the knee
• Arthroscopy: Arthroscopy involves the introduction of pencil-like instruments connected to a video monitor, which allow washing and smoothing of the degenerated knee that grinds, catches, and locks
• Partial Knee Replacement: There are two main forms of this type of procedure. Please note that choosing between a partial and a total knee replacement is a complex medical decision requiring the careful consideration of many factors. A surgeon will discuss these options with the patient and, after considering the severity of the existing condition, age, lifestyle, and other factors, recommend one of the following:

• Total Knee Replacement: A replacement knee has three parts - the metallic cap that covers the end of the thigh bone (femur); the plastic tray that covers the flat, top portion of the shin bone (tibia); and the plastic piece affixed to the underside of the kneecap (patella). In the last twenty years, the plastic that covers the top of the shinbone has begun to be placed onto a metallic tray, which is then affixed to the bone.
  
  The term “total knee replacement” can be somewhat misleading because it conjures up the image of big chunks of bone being removed. In reality, only slivers of bone are removed. The end of the thighbone is shaped into connecting flat surfaces that will match a metallic cap, and a fraction of an inch is removed from the upper shin.
  
  The kneecap is a hard bone with a very soft cartilaginous underbelly. This cartilage can wear out just like any other cartilage in the knee. In the total knee replacement, the worn out cartilage of the kneecap is removed along with a portion of the underlying bone and replaced with a plastic button. The kneecap is then said to have been resurfaced. Not all knee replacement surgeries require kneecap resurfacing.
  
  A knee replacement can be performed by way of the traditional incision that measures approximately 12 inches, a moderate incision measuring approximately 5 to 6 inches, or a mini-incision that is 3 to 4 inches long. Nearly all knee replacements can be performed via the moderate or mini-incision. The length of the incision is dictated by the size of the leg, the complexity of the specific procedure, and the philosophy of the surgeon.

Cartilage cultures and grafts [including autologous chondrocyte implantation (ACI), Genzyme Biosurgery options like Carticel, and osteoarticular transfer system (OATS) procedure], which replace deficient articular cartilage with fresh sources, are potential options for patients with cartilage injuries.

Plastic and metallic caps that plug deficient areas are also available.

At Mount Sinai, we offer a number of different treatments for ligament injuries, including:

• ACL (Anterior Cruciate Ligament) reconstruction with bone-patella-bone graft
• ACL  reconstruction with hamstring graft: Of the two tendons utilized in a hamstring graft, only one – the semitendinosus- is actually a hamstring. The other – the gracilis- is not
• ACL reconstruction with a variety of allografts
• ACL reconstruction in teenagers
• PCL / LCL reconstruction

Since a torn ACL cannot be sewn back together, it is reconstructed through the use of a substitute ligament. Substitutes can come from a patient’s own body (as in the case of an autograft), or from a tissue bank (as in an allograft). Substitute ligaments may also be synthetic. Synthetics are appealing, but those that have been tried in the United States have not worked.

Allografts have an obvious advantage of leaving a patient’s own body intact. Cadaveric allografts are expensive, however, and carry with them a small chance of disease transmission. The sterilization process used for allografts can also leave them relatively stiff.

Allografts tend to be used when multiple grafts are needed, or when a patient undergoing a second operation has already used an autograft in their previous procedure. There are some surgeons, though, that utilize allografts on all patients in need of an ACL surgery.

Autografts have three sources: the patellar tendon, the so-called hamstring tendons, and the quadriceps tendon (in order of current popularity).

The patellar tendon graft includes the middle third of the tendon connecting the kneecap (patella) to the tibial tuberosity (the knob at the top of the shin bone), as well as a piece of bone at each end of the tendon. One piece of bone comes off the kneecap and the other comes off the tuberosity. Once the graft is harvested, it has to be placed inside the knee. To accomplish this, holes (also known as tunnels) are created through which the graft is passed. The graft is then locked to one of the tunnels, made taut, and, finally, fixed to the other tunnel. A screw is placed in the tunnels, thus wedging the bone from the graft to the walls of the tendon. This procedure carries with it a potential risk of kneecap fractures.

Bone-patella-bone graft taken from the kneecap ligament at the front of the knee.

The "hamstring graft" harvests the semitendinosus hamstring along with the gracilis tendon, which runs along the inner thigh. The two remaining hamstrings are left untouched. Soft tissue screws are available for the fixation of these grafts, as are a host of small metallic and plastic devices.

“Hamstring graft”. Only one of the two tendons is a hamstring (the lower one – the semitendinosus)

The quadriceps tendon graft uses the tendon that joins the quadriceps muscles at the front of the thigh to the kneecap. It has some of the advantages and disadvantages of the other two grafts and is equally acceptable.

At the present time, a surgeon’s comfort level with a certain graft is probably more important than the actual graft itself.

Rehabilitation has changed greatly over the past 20 years. Previously, people undergoing ligament surgery were placed in a long leg cast, which we now feel is unnecessary and possibly harmful. Today, someone undergoing ACL surgery starts one form of therapy right away. The most important part of therapy is restoring normal bending and straightening of the knee. After surgery, this can be difficult, as the operated knee generally does not want to move, preferring to stay slightly bent when left alone. Some people will also find the rehabilitation process more difficult than others. When the knee hurts, the muscles tend to atrophy and the tendons tighten up. Therapists work with patients to reverse that process.

Activities that include uncontrolled jumping and twisting put the reconstructed ligament at risk for re-injury. As such, these are the last to be permitted. However, simple running, cycling, jumping in place with both feet, and even side to side jumping are allowed early on. Swimming is also permissible immediately after surgery.

The graft that was just placed in the knee needs time to start looking and acting like an ACL. Opinions are divided with regards to how long this takes, with the customary wait being one year before resuming contact sports.

At this point, the very long-term effects of harvesting a graft of any kind are not known.

For meniscus injuries, we provide:

• Arthroscopy
• Partial excision of torn meniscus
• Repair of meniscus
• Allograft

For patients who have experienced bone fractures, our specialties include:

• Fractures of the lower femur
• Fractures of the upper tibia
• Fractures of the patella
• Pediatric/teen injuries: We treat a range of different pediatric and teen conditions, such as tibial spine/tibial eminence (arthroscopic) and tibial tuberosity

Kneecap (Patella) Disorders and Chondromalacia
Patients that suffer from knee cap disorders and chondromalacia (poor kneecap alignment) have a number of different treatment options from which to choose, including:

• Surgery (on previously operated kneecaps)
• Arthroscopy (the introduction of pencil-like instruments connected to a video monitor)
• Lateral retinacular release (division of the lateral retinaculum)
• Facetectomy (removal of a small portion of the patella)
• Proximal re-alignment (tightening or reconstruction of the soft tissues around the kneecap)
• MPFL reconstructions (reconstruction of the medial patellofemoral ligament)
• Reconstruction (of the lateral retinaculum)
• Fulkerson/Maquet/Elmslie-Trillat/Cox Procedures (operations that displace the tibial tuberosity)
• Quadriceps/Patellar tendon repairs (for disruptions or tears of the quadriceps or patellar tendons)
• Patellofemoral replacement
• Lowering of the kneecap (for high-riding kneecaps)
• Raising of kneecap (for patella baja)
• Trochleoplasty (reshaping of the trochlear groove)
• Repair of fractures

Kneecap Surgery
Patients often need surgery either because they have failed a thorough non-operative program, the kneecap malalignment is truly severe, or their kneecap is very arthritic.

Kneecap operations are divided into those that re-align the kneecap and those that do not. Re-alignment operations are performed when the kneecap is felt to be out of place. These operations can also be performed if the cartilage under the kneecap is unhealthy, and if the surgeon feels that moving the kneecap one way or the other might remove pressure from these unhealthy areas.

The orthopedic community distinguishes between proximal (close to the center of the body) and distal (far from the center of the body) re-alignment operations. Proximal procedures involve surgery on the tissues that surround the kneecap, while distal re-alignments are performed further down on the tibial tuberosity – the bump at the top of the tibia (shinbone) where the kneecap ligament attaches.

Proximal re-alignments include:

• The lateral retinacular release (commonly known as a "lateral release"): When the lateral retinaculum is tight, it tugs on the kneecap. The kneecap then becomes tilted and/or pulled to the side. Thus, the concept of the lateral release is relatively simple. In this procedure, as described in the 1970s by Ficat in France and Merchant in the United States, the lateral retinaculum is cut as it inserts onto the kneecap and the kneecap tendon.
  
  The enthusiasm for this operation has been tempered by the realization that, despite its simplicity, it is not completely innocuous. Coursing through the lateral retinaculum are a group of blood vessels that readily bleed when cut. Known as the geniculate vessels, these can be a source of bleeding inside the knee even after the operation has ended. This is not a serious complication, but it may require the surgeon to “tap” the knee, or place a needle into the joint to draw out the blood.
  
  Currently, the role of the isolated lateral release is a hotly contested issue in the world of orthopedics, as there are a number of reasons why such a procedure may not work by itself. First, the operation is rarely performed as it was initially described. Instead of extending from the top of the kneecap down to the tibial tuberosity (the top of the shin), most lateral releases only go half that distance, while the original operation involved a significant incision down the middle of the knee. This is because that is as far as you can go with a small incision or an arthroscopy. Therefore, the release as it is performed today is incomplete relative to the original version, and the kneecap is not released as much.
  
  A second limitation of the lateral release is that it does not predictably correct all that is wrong. In the same way that a lateral retinaculum might be tight, the medial retinaculum might be lax while the vastus medialis obliquus (VMO) muscle is also deficient. The Q angle (the relationship and alignment between the pelvis, leg, and foot) is occasionally very elevated, and arthritic lesions may be present under the kneecap or in the trochlea. The kneecap can lie too high (patella alta) or too low (patella baja, or infera). The trochlea can also be convex instead of concave. With the exception of very specific arthritic lesions, the lateral release will not address any of these deficiencies.
  
  
  

  Arthroscopic view of a lateral release. The arrows show the
  two sides of the lateral retinaculum that were together prior
  to the release
  
  
• The medial plication/vastus medialis obliquus (VMO) advancement: The medial retinaculum and vastus medialis obliquus (VMO) are sometimes deficient. To address this, the medial retinaculum is detached from the kneecap and then re-attached over the kneecap. The kneecap is thus pulled medially (towards the inside). This operation is often performed in conjunction with a lateral release; as such, it requires a separate incision. An alternative is an incision down the middle of the knee that gives the surgeon access to both sides of the kneecap. The medial plication can also be performed arthroscopically, though this is not uniformly recommended.
  
• Distal re-alignments: There are several different types of these procedures.
  
  The first, known in the United States as the Elmslie-Trillat operation, involves moving the tibial tuberosity medially (to the inside). Patients whose tuberosities are abnormally positioned are the best candidates for this procedure. When the tibial tuberosity is moved to its new position, it needs to be fixed with one or two screws, and the patient has to limit his or her activities for 6 to 12 weeks until the tuberosity has healed in its new position. Depending on how solidly fixed these screws are, a cast or soft knee immobilizer will be used until the tuberosity has sufficiently healed.
  
  A second type of distal re-alignment is known as the Maquet, a tibial tuberosity operation named after the Belgian surgeon who first described it. As of this writing, it has lost much of its popularity in Europe, though it still remains an accepted procedure. It is designed to lift the kneecap out of the trochlear groove, thus removing pressure. Unfortunately, it mostly lifts the nose (distal pole) of the kneecap and does not predictably relieve pain. To carry out the operation, the tibial tuberosity is partially split off from the underlying shinbone, and a piece of bone is inserted between the two, thus elevating the tuberosity. Since the patellar tendon inserts itself onto the tuberosity, the tendon is elevated, and, since the tendon starts at the tip of the kneecap, the tip of the kneecap is elevated. There are, however, a number of controversies surrounding this procedure, including how much to elevate the tuberosity, where the bone should come from, what bone substitutes are acceptable, how the Maquet procedure should be fixed until it heals, and what the current indicators for the operation are.
  
  The Fulkerson (AMZ) is a combination of the two tibial tuberosity transfers described above. The tuberosity is both elevated and transposed medially (to the inside) through a single oblique cut between the tuberosity and the underlying bone. It combines the advantages and disadvantages of the Elmslie-Trillat and of the Maquet, and is therefore equally controversial. The most controversial aspect of the operation is its use in patients whose tibial tuberosity is already normally positioned.
  
  Finally, the distal transfer is performed if the kneecap sits too high in the groove (patella alta). The tibial tuberosity can then be brought distally (down towards the foot) by one or two centimeters.
  
  These distal re-alignments can all be performed with any of the proximal re-alignments. This makes for a wide variety of surgical combinations. A knowledgeable surgeon will consider all options to put together the best possible surgical treatment for the patient.
  
  

  Distal re-alignment options (reprinted with permission from Grelsamer RP, Weinstein C: Patellar Instability. Chapter 59 in The Adult Knee. Callaghan JJ, Rosenberg AG, Rubash HE, Simonian PT, Wickewicz TA, Ed. Lippincott, Williams & Wilkins, 2003)

We offer osteonecrosis patients the best possible chance at a full recovery with the following procedures:

• Arthroscopic Drilling
• Partial knee replacement ("Unicompartmental” replacement
• Total knee replacement