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Tuesday, November 22, 2011

Knee Surgery - A Guide for Patients and Healthcare Professionals

Justin D. Harris, MD
Orthopaedic Surgeon
Lincoln, NE

This knol provides a general overview of sports-related knee injuries. It is intended to provide basic information for patients and other healthcare professionals regarding the most commonly treated knee conditions.

Mechanism of injury, symptomatology, treatment options, and basic rehabilitation principles are discussed for each condition.


Knee injuries and knee pain are extremely common. Knee problems are the most common reason patients need to see an orthopaedic surgeon. The knee is an extremely complex joint that is subjected to large forces during daily and athletic activities. Sports injuries frequently involve the knee, and as we age, degenerative knee problems develop. Many knee injuries can be treated conservatively (without surgery), but certain knee conditions benefit from surgical intervention.

Anatomy and Function

The knee is the largest joint in the body. Knee function primarily involves bending (flexion) and straightening (extending) the leg. Rotation also occurs within the knee. Anatomically, it is composed of the lower end of the thigh bone (distal femur) and upper end of the shin bone (proximal tibia). The front of the knee is covered by the knee cap (patella) that slides in a groove in the distal femur (trochlea) during knee motion.

The ends of the femur and the tibia, as well as the undersurface of the patella, are covered with cartilage. This cartilage has been described as the “white on the end of a chicken bone.” This “articular cartilage” serves to help with joint motion by providing lubrication and minimizing friction. Deterioration or wear of this articular cartilage is termed arthritis.

The knee also contains two “shock-absorber” pieces of cartilage called menisci. The medial meniscus sits between the femur and the tibia on the inner part of the knee, whereas the lateral meniscus occupies the outer part of the joint. Meniscal function is to provide cushion for the bones of the knee.

Knee stability is provided the ligaments of the knee. The cruciate ligaments (ACL and PCL) are in the center of the knee and serve to resist translational and rotational moments about the knee. The medial collateral ligament (MCL) is on the inner part of the knee connecting the femur and the tibia. The lateral collateral ligament (LCL) is on the outer part of the knee. The collateral ligaments resist side-to-side movements about the knee.

Lastly, the quadriceps tendon and the patellar tendon make up the extensor mechanism of the knee. The quadriceps are the muscles on the front of the thigh. At the knee, they form a tendon that inserts on the knee cap. There is a second tendon that runs from the knee cap to the top of the tibia (shin bone). These tendons as well as the patella allow us to straighten the knee from a bent position.


Orthopaedic Knee Evaluation
The orthopaedic knee evaluation typically involves a detailed medical history, a thorough knee examination, and imaging studies. The medical history involves questions about the patient’s health as well as details regarding their knee symptoms. Important factors to consider are the duration and intensity of symptoms. The location and quality of the pain are also important. Knee conditions may often involve swelling, mechanical symptoms (popping, catching, locking), and sensations of instability. Alleviating and aggravating factors are important to mention.

The knee evaluation involves checking the back and the hip to ensure that the pain is coming from the knee. Inspection of the muscles and the alignment of the leg is next. Range of motion and walking observation follow. The surgeon will then palpate specific areas of tenderness to try to determine the location of the pathology. Lastly, specific tests are performed to assess the quality of various tissues in and about the knee (menisci and ligaments).

Most surgeons will order x-rays to look at the bony structures of the knee. Fractures, leg malalignment, and arthritis will often be noted on x-rays. Soft tissue structures (cartilage, menisci, and ligaments) are best evaluated with an MRI.

After compiling all the information from the history, physical examination, and imaging studies, the orthopaedic surgeon will make a diagnosis and present
a treatment plan. Treatment options may include medications, physical therapy, or orthotics. Surgery may be recommended. The surgeon will then describe the surgical procedure, explain the risks and benefits associated with the procedure, and detail the expected postoperative recovery.

Knee Surgery
Various injuries and conditions within the knee are treated operatively. Indications for surgical treatment vary, based on individual diagnosis. Certain conditions may fail to respond to conservative management, whereas other injuries are treated more aggressively. The goal of all treatment is to try to return the patient to their previous level of activity and function.

Knee surgery can be performed arthroscopically or in an open fashion. Arthroscopic surgery allows an orthopaedic surgeon to diagnose and treat knee injuries by viewing the inside of the knee through small incisions using a pencil-sized instrument called an arthroscope. The knee is filled with fluid and the scope transmits an image of the knee through a camera to a television monitor. During the procedure, additional small incisions are created to allow insertion of other small instruments to remove or repair damaged tissues. Most arthroscopic knee procedures are done as an outpatient. Recovery is typically much quicker and easier than traditional open knee procedures.

Open knee surgery involves larger incisions to enter the knee joint (arthrotomy).

These operations are more extensive and often more complex than most arthroscopic procedures. They may be done as an outpatient, but a short inpatient stay afterward is not uncommon.

Rehabilitation for knee injuries and after knee surgery varies based on the patient’s specific injury complex and the surgical procedure that was performed. Physical therapy can be utilized as a nonoperative modality for a number of knee conditions. The primary goals of PT for knee pain include maximizing range of motion, improving flexibility, and strengthening the muscles around the knee to take stress off of injured tissues.

Postoperative rehab can be quite variable. Some simple knee surgeries don’t require formal therapy at all, whereas other procedures require months of dedicated physical therapy to achieve maximum results.

A more detailed description of individual surgical procedures and the expected postoperative recovery follows.

Meniscal Injuries
Meniscal injuries are the most commonly surgically-treated knee condition. The menisci are shock-absorber cartilage between the femur and the tibia. The medial meniscus is on the inner portion of the knee, whereas the lateral meniscus is on the outer part of the knee. Young patients typically sustain meniscal injuries during athletic activities. Cutting and pivoting can stress the meniscus to the point that it tears. Older patients tear their menisci during less vigorous activities. As we age, the meniscus starts to degenerate and can tear with trivial trauma. A large percentage of older patients actually have asymptomatic meniscal tears.

Symptoms of a torn meniscus include recurrent swelling (effusions), mechanical symptoms (popping, catching, and locking), and pain with deep squatting. The pain is typically localized to one side of the knee or the other. A medial meniscus tear hurts on the inside of the knee, while a lateral meniscal tear hurts on the outside. Cutting, pivoting, and athletic activities may be difficult with a meniscus tear.

Surgery for a torn meniscus is typically done arthroscopically. The specific surgical procedure that is performed is dependent on a number of factors. It is important to try to preserve meniscal tissue because arthritis tends to develop faster in knees that have less meniscus remaining.

Meniscus tears that occur in young patients and are located near the edge of the meniscus (best blood supply) are often repairable. Meniscus tears near the central surface and those that occur in older patients are often removed (partial meniscectomy) because they lack the capacity to heal. In some select situations, patients that have had a significant portion of their meniscus removed may be a candidate for a meniscal transplant, where a cadaver meniscus is placed in the knee to try to prevent joint degeneration.

Partial Meniscectomy
Arthroscopic partial meniscectomy is the most common arthroscopic procedure that surgeons perform. Patients that have symptomatic meniscal tears are usually good candidates for arthroscopic surgery. If a surgeon determines that a meniscal tear is unlikely to heal, the torn meniscal tissue is removed surgically. This is called a partial meniscectomy. (Fi

Partial meniscectomies are performed arthroscopically. Once the torn tissue has been removed from the knee, patients typically feel much improved. The postoperative course is fairly straightforward. Most patients are on crutches for a couple of days to help stabilize the knee. Once the swelling subsides, the rehabilitation progresses quickly. Most patients can return to work after only a few days. Return to sports is permitted once the swelling is gone, and the patient has normal quadriceps function.

Video of a partial medial meniscectomy

More video of a partial medial meniscectomy

Meniscal Repair
Meniscus repairs are typically reserved for younger patients (< 40 years of age) who have a tear that is located near the outer rim of the meniscus. The goal of all meniscal surgery is to preserve meniscal tissue, but repairs are only indicated where healing can be expected.

Surgeons employ various meniscal repair techniques. The basic principles involve placing suture or some type of bioabsorbable implant across the tear, which will stabilize it until it heals. Smaller tears are amenable to repairs with meniscal fixation devices placed arthroscopically (all-inside). Larger tears occasionally require a secondary incision on the side of the knee (inside-out). Results of successful healing after meniscal repair vary from 60%-80%.

The postoperative rehabilitation following a meniscal repair will vary based on surgeon preference, but basic guidelines are usually followed. The meniscus typically takes a few months to be fully healed so the repair must be protected during that time. Most patients are placed in a hinged-knee brace at the time of surgery. They can bear weight within the brace but usually only locked in full extension (leg straight). Range-of-motion exercises are allowed but higher degrees of flexion are usually avoided (< 90).

After the first month the brace is unlocked during weight bearing, and higher knee flexion is permissible. Most patients are allowed to return to sports anywhere from 3 to 6 months after surgery, depending on the severity of the tear.

Ligament Injuries
There are four main ligaments around the knee. The ACL, PCL, MCL, and LCL have been described previously. Injuries to these structures are not uncommon. As we have become a more active and a more sports-oriented society, the incidence of knee ligament injuries has increased. Treatment of knee ligament injuries is based on multiple factors. Each individual ligament is treated differently. Patient age, health, and activity level all play a role in determining optimal treatment. Additional pathology within the knee can also alter the treatment plan.

Anterior Cruciate Ligament Injuries

ACL injuries occur through some form of twisting mechanism. This can occur while the foot is planted on the ground or after landing awkwardly from a jump. Additionally, a “contact” injury can occur where the knee is forced in an abnormal position by an outside stress.

Acute symptoms of an ACL injury include hearing or feeling “a pop.” Swelling of the knee can develop quite quickly. In chronic settings, knee instability becomes more common, especially during cutting and pivoting activities.

The treatment of ACL injuries is dictated by the patient’s activity level and expectations. Patients who live a sedentary lifestyle may not need to have their ACL tear treated surgically. However, athletes who wish to regain the ability to participate in cutting and pivoting sports will likely benefit from ACL surgery.

Anterior Cruciate Ligament Reconstruction
Anterior cruciate ligament tears usually cannot be repaired. As such, a reconstruction or “ACL replacement” must be performed. The most common type of ACL reconstruction involves taking tissue and creating a new ligament which is then placed within the knee. This serves to replace the torn ACL.

The most concerning issue for patients undergoing ACL reconstruction is the graft source. The new ACL can come from the patient (autograft) or it can come from a cadaver (allograft). There are risks and benefits to both options. The most common autograft options are patellar tendon and hamstrings.

ACL reconstruction is typically done as an outpatient procedure. Depending on graft choice, open incisions may be necessary to harvest the tissue that is to be used as the new ACL. Knee arthroscopy is then performed to inspect the knee, treat additional injuries (meniscus tears or cartilage damage), and to prepare the knee for the new ACL.

Once the graft tissue has been prepared and the torn ACL tissue has been removed, the surgeon is ready to place the ligament within the knee. Small tunnels (7-10 mm) are drilled in the tibia and the femur to allow the ligament to be pulled up into the knee.

Accurate placement of these tunnels is critical to successful ACL surgery. After the ACL graft is in position, fixation devices (screws, washers, buttons, etc.) are used to keep it there until it can heal into place.

Rehabilitation after ACL reconstruction is a necessary part of a successful procedure. The patient is placed in a brace after surgery. Therapy is started shortly thereafter. Weight bearing is typically allowed immediately. Maintaining full extension and minimizing swelling are early goals. Range of motion activities then begin. Strengthening of the leg comes next, with gradual return to straight ahead running. Sport specific rehab and cutting and pivoting are the last steps prior to return to athletics. The typical athlete is held out of sports for 6 months following ACL reconstruction.

Posterior Cruciate Ligament Injuries
Posterior cruciate ligament (PCL) injuries are much less common than ACL tears. The most common mechanism of injury involves a direct blow to the front of the tibia. This can occur during sports or in motor vehicle collisions. The tibia is forced backwards relative to the femur and the PCL tears. Other common athletic mechanisms include knee hyperextension and forced knee flexion with the foot plantar flexed. Acutely, PCL tears can present similarly to other knee injuries. Swelling, pain, and instability are common. In the chronic setting, persistent instability may occur.

Management of isolated PCL tears is typically conservative. Once the acute swelling and discomfort of the initial trauma subsides, physical therapy is utilized to try and maximize quadriceps strength to assist with dynamic knee stability. After completion of a dedicated rehab program, the patient is allowed to return to play once full motion and near-normal strength have returned.

Posterior Cruciate Ligament Reconstruction
PCL surgery is much less common than ACL surgery. Surgical intervention is typically reserved for specific indications. PCL tears that pull a piece of bone off of the tibia (avulsion fracture) may benefit from operative fixation. PCL injuries that occur in conjunction with other knee ligament tears (knee dislocations) often benefit from surgical reconstruction. Finally, patients who have had PCL tears treated conservatively, but still complain of instability are candidates for PCL reconstruction.

PCL reconstruction involves taking tissue from another source and creating a new PCL. Autograft or allograft sources can be used to make the PCL graft. Graft choice is determined after a discussion of risks and benefits of each option between the patient and the treating orthopaedic surgeon. Isolated PCL reconstruction can often be done as an outpatient procedure, whereas multiple ligament knee surgery typically requires a short hospital stay. PCL surgery is usually done as an arthroscopic procedure, although some small open incisions are often required. An added degree of difficulty exists when compared with ACL reconstruction, because the PCL attachment site on the tibia can be more challenging to access. Just as in ACL reconstruction, the torn PCL is removed arthroscopically. Tunnels are then drilled in the tibia and the femur to allow passage of the PCL graft. The new PCL is then pulled into the knee and fixed to the bone.

Rehabilitation after PCL reconstruction varies based on surgeon preference. Braces are typically worn in the early postoperative period. Weight bearing may be delayed in some instances. Postoperative therapy focuses on quadriceps strengthening to prevent the tibia from sagging backward, which can stretch the PCL graft. Most patients return to sports and full activity 6-8 months after surgery

Medial Collateral Ligament Injuries
Medial collateral ligament (MCL) injuries occur when the knee buckles to the inside. This often happens when an athlete sustains a direct blow to the outside of the knee forcing it inward. Pain is felt on the inner (medial) part of the knee. Noncontact injuries often result in isolated partial MCL tears, whereas contact mechanisms can produce complete MCL tears and may injure other knee ligaments as well (ACL).

The most common symptom following a medial collateral ligament injury is pain directly over the ligament. Swelling over the torn ligament may appear, and bruising and generalized joint swelling are common 1 to 2 days after the injury. In more severe injuries, patients may complain that the knee is unstable, or feel as though their knee may “give out” or buckle.

The majority of MCL injuries are treated conservatively (without surgery). The duration of convalescence is dependent on the severity of the injury. Partial MCL tears usually heal quickly and athletes return to play within a couple of weeks. Minimizing swelling and maintaining range of motion are essential to facilitate a quick recovery. Complete MCL tears may take more than 6 weeks to heal. Pain, swelling, and stiffness are common. Bracing is usually utilized to help the ligament heal under normal tension. Range of motion exercises are emphasized during rehab to prevent knee stiffness from developing. Complete rehab from a full thickness MCL tear can take 3-4 months in some situations.

Medial Collateral Ligament Repair/Reconstruction
As stated previously, most MCL injuries don’t require surgery. However, certain surgical indications do exist. High-grade (complete) MCL tears that coexist with other knee ligament injuries may benefit from surgical repair. Additionally, MCL tears that have healed with residual laxity (looseness), causing persistent instability of the knee, often benefit from repair or reconstruction.

MCL surgery is done via an open incision on the inner portion of the knee. If the operation is done in the acute setting (< 3 weeks after injury), primary repair of the torn ligament is possible. Midsubstance ruptures are reapproximated (connected) and sutured together with large caliber permanent suture material. Tears that pull of off the ligament’s bony attachment sites are usually put back down to the bone with suture anchors.

In cases of chronic MCL laxity and instability, MCL reconstruction is often necessary. In these instances, a new MCL is fashioned from autograft or allograft tissue. The new ligament is then placed over the top of the old MCL and secured to the femur and the tibia with fixation devices.

Rehabilitation after MCL surgery is similar to that of other knee ligament postoperative protocols. The knee is protected in a brace for a few weeks after surgery. Range of motion exercises are initiated early to prevent stiffness. Strengthening begins 6-8 weeks after surgery. Complete rehab takes 4-6 months.

Lateral Collateral Ligament/Posterolateral Corner Injuries
Lateral collateral ligament (LCL) injuries occur when the knee buckles outward. These are typically high-energy contact injuries where a force is applied to the inner part of the knee which then stretches or tears the ligament on the outside. Pain is felt on the outer part of the knee over the LCL. Symptoms are similar to other knee ligament injuries.

Isolated LCL injuries do well with conservative management. Rest, icing, and early motion permit a relatively quick return to sports and activity. Unfortunately, injuries to the lateral side of the knee often produce more trauma than just isolated LCL tears. The posterolateral corner (PLC) is a complex of ligamentous structures behind the LCL that serve to resist varus (outward) stress, posterior (backward) displacement of the tibia, as well as external rotation of the knee. PLC injuries typically occur in conjunction with other knee ligament injuries. They are often misdiagnosed and can play a role in why other ligament surgery (ACL/PCL) fails.

Lateral Collateral Ligament/Posterolateral Corner Repair/Reconstruction
Surgery for the LCL/PLC is typically reserved for knees with multiple ligaments that are injured. Common combinations include ACL/PLC injuries and PCL/PLC injuries. Knee dislocations often have PLC involvement as well. In most settings, if the LCL/PLC is ignored, the results of cruciate reconstruction will be diminished. Lateral-sided knee injuries are repaired through open incisions. For acute injuries, primary repair of the PLC is possible. The tendons and ligaments that are injured are sutured together primarily or are reattached back to their insertion points on the bony structures. In the chronic setting, the LCL and PLC have healed and scarred together with residual laxity. Primary repair is not possible. As such, reconstruction is then performed with autograft or allograft tissue. Multiple reconstruction techniques have been described. Postoperative management is similar to that described above.

Articular Cartilage Injuries
Articular cartilage is the smooth, glistening, white tissue that covers the ends of bones in the human body. It functions to resist compressive loads in joints and provides a smooth surface with low friction to allow for supple joint movement. Injury to articular cartilage is extremely common. Traumatic events can damage cartilage, and as we age, the biology of the cartilage changes, predisposing it to wear and injury. Cartilage injuries are concerning because articular cartilage lacks a blood supply, which prevents it from healing.

Articular cartilage injuries can occur as a result of either traumatic mechanical destruction, or progressive mechanical degeneration (wear & tear). ACL tears, patellar dislocations, and other knee injuries can present with acute articular cartilage damage. Typically, these mechanisms of injury create small, focal defects in the cartilage. Degenerative cartilage lesions can be shallower but often involve more overall surface area. Additionally, osteochondritis dissecans (OCD) is a condition where the bone behind the articular cartilage is diseased, which may lead to a large defect if a piece of cartilage were to detach from the underlying bone.

Symptoms of articular cartilage damage include knee swelling and vague pain. Mechanical symptoms (catching and locking) may also be present. With mechanical degeneration (wear and tear), the patient often experiences stiffness, decreased range of motion, joint pain and/or swelling.

Cartilage injury is difficult to diagnose by history and physical exam alone. Radiographs (x-rays) and an MRI of the knee are helpful to evaluate the health of the cartilage. X-rays are used to look for moderate to severe signs of arthritis (diffuse cartilage degeneration). MRI is helpful to look for focal cartilage lesions as well as to look for loose bodies (pieces of cartilage that have detached and are floating in the knee) and additional pathology within the knee.

Treatment of articular cartilage lesions is dependent on multiple factors. Patient age, activity level, and mechanism of injury commonly dictate management. Young patients with traumatic injuries are treated aggressively to try to restore a normal articular surface within the knee. Older patients with degenerative cartilage problems can initially be treated conservatively.

Nonoperative treatment is indicated for patients who present with diffuse osteoarthritis. Management consists of physical therapy, medications activity modification, orthotics, bracing, and injections. Failure of conservative management may be an indication for surgical intervention, depending on the patient’s symptomatology.

Operative management for cartilage injuries is reserved for acute traumatic defects, OCD lesions that are deemed to be unstable (at risk for detachment), and loose bodies within the knee. Small focal lesions can be treated conservatively, but this is usually unsuccessful. Large lesions should be treated aggressively to prevent joint deterioration. The specific surgical procedure to treat articular cartilage lesions is dictated by the lesion size, the quality of the bone behind the lesion, and surgeon preference.

Loose Body Removal
Loose bodies within the knee often cause symptoms of pain, catching, and locking. Symptomatic loose bodies should be removed. This is performed as an outpatient, arthroscopic procedure. The surgeon uses the arthroscope to find and localize the loose bodies and they are removed with an arthroscopic grasper. The remainder of the knee is evaluated and any additional pathology is treated appropriately.

Rehab after simple loose body removal is fairly straightforward. Crutches may be needed for a couple of days, but patients are allowed to return to full activity once swelling and range of motion have normalized.

Arthroscopic Chondroplasty
Arthroscopic chondroplasty is commonly performed during knee arthroscopy. It is utilized for treating incidentally-found chondral lesions during surgery. It can also be utilized for small areas of superficial cartilage damage in patients that experience joint pain and have associated mechanical symptoms. Loose cartilage flaps and debris within the knee are removed using an arthroscopic shaver. Great care is taken to avoid damaging normal cartilage. The goal of surgery is to eliminate catching and locking from these loose pieces of cartilage and to try to prevent propagation of these chondral flaps. The postoperative management is identical to that of basic knee arthroscopic procedures described previously.

Small, focal lesions (< 2 cm) of cartilage damage that are surrounded by healthy tissue are often treated with a microfracture procedure. As cartilage has no blood supply, it lacks the ability to heal. The bone beneath the cartilage, however, has a rich blood supply. Microfracture procedures try to access the osseous vascular supply in order to heal cartilage defects. Microfracture creates small holes in the bone at the base of a cartilage lesion. This allows cells from the bone marrow to fill in the defect and stimulate new cartilage growth. This new cartilage is a scar-type of cartilage called fibrocartilage. It is less durable than normal hyaline cartilage, but provides a smooth covering of the lesion.

Indications for microfracture are small to moderately-sized focal cartilage lesions. Widespread cartilage damage is a contraindication to a microfracture procedure. It is done arthroscopically. The cartilage defect is evaluated and measured by the surgeon. Loose cartilage flaps are removed with a shaver. Then, a small, sharp pick (awl) is used to create the small microfracture holes in the bone. The number of microfracture holes created depends on the size of the area being treated. Most patients with a 1- to 2-centimeter area of damage require 5 to 15 small holes in the bone.

The postoperative management of a microfracture procedure is critical. Surgery is typically done as an outpatient. The patient is kept non-weight bearing and on crutches for 6-8 weeks following surgery. Range of motion is essential after surgery to allow the fibrocartilage to grow and mature into a normal shape. Many surgeons will use a CPM (continuous passive motion) machine after surgery to facilitate this. Microfracture done in the area of the kneecap (patellofemoral joint) is rehabilitated somewhat differently, in that motion is restricted to avoid excess pressure placed on the healing area.

Autologous Chondrocyte Implantation
Another option for attempting to heal cartilage lesions is autologous chondrocyte implantation (ACI). This procedure is reserved for patients with small to moderate-sized lesions who have usually failed a previous procedure (chondroplasty or microfracture). The procedure is complex, and the rehab is extensive so appropriate patient selection is critical. It is a two-stage operation in which cartilage cells are harvested from the knee, grown in a lab, and then reimplanted into the knee during a second operation.

The first step of an ACI surgery is to perform an arthroscopic procedure where the cartilage defect is evaluated. If the lesion is appropriate for ACI (based on size, depth, and quality of the surrounding cartilage), small pieces of normal cartilage are harvested from less essential areas of the knee. This cartilage is then sent to a cartilage expansion laboratory where the cells are cultured and multiplied. Once enough cells have been grown, the second stage of the operation is scheduled.

The second stage of ACI surgery involves implantation of the cartilage cells. This is done as an open procedure. The area of cartilage damage is exposed and sized. A second incision is then made over the shin and a “patch” is harvested from the thick tissue (periosteum) that covers the shin bone. This patch is roughly the size of the cartilage lesion being treated. The patch is then sewn over the cartilage defect and the cultured cells are injected underneath the periosteal patch.

The rehab after ACI is similar to that of microfracture. Weight-bearing is restricted and crutches are required for 6-8 weeks while the cells adhere to the underlying bone. Motion is encouraged, often with the use of a CPM. Training intensity increases from 3-6 months postoperatively, but most athletes don’t return to sports for 12-16 months following surgery.

Osteochondral Autograft Transfer
Another surgical option for symptomatic, focal articular cartilage lesions is an osteochondral autograft transfer. This is also referred to as a mosaicplasty, or an OATS procedure. Mosaicplasty involves harvesting normal cartilage from the knee and transferring it to replace the area of damaged cartilage.

Indications for mosaicplasty are similar to that of ACI. Lesions < 2 cm in diameter are ideal. This is not a procedure utilized to treat diffuse cartilage damage. The surgery can be done arthroscopically or open. It is commonly performed as an outpatient. The cartilage defect is usually evaluated and prepared arthroscopically. If the lesion is appropriate for mosaicplasty, appropriately-sized osteochondral plugs are harvested from another part of the knee joint. The cartilage in this “donor area” is not as essential because it is subjected to less pressure during weight-bearing. The plugs are then transferred to the cartilage defect and set into place.
The rehab after osteochondral autograft transfer is similar to that described previously. Weight bearing is restricted for 6-8 weeks. Motion is encouraged. Return to sports and full activity is permitted after 6 months of rehab in most cases.

Osteochondral Allograft Transplantation
Large, focal cartilage lesions (> 2 cm in diameter) are often too large to be treated with microfracture, ACI, or mosaicplasty. For these patients, an allograft is often the only tissue source large enough to provide enough cartilage to cover the defect. An allograft is donated tissue that comes from a cadaver. Patients who are candidates for allograft transplantation have their imaging studies (x-rays or MRI) sent to a tissue bank which tries to procure a graft that is size matched to the patient. When a graft is found, surgery is scheduled.

Osteochondral allograft transplantation is typically done as an open procedure. A short hospital stay is not uncommon. The area of damaged cartilage is prepared by coring a socket 4-5 mm deep into the subchondral bone. The exact same location is then identified on the allograft specimen and a plug is created that fits perfectly into the host femur. The allograft plug is then placed within the recipient socket. The goal is to create a flush, smooth surface of articular cartilage.

The postoperative management of osteochondral allograft transplantation is slower than that of other cartilage restoration procedures. The bony portion of the graft needs to be replaced by bone from the patient, and while this occurs the graft is susceptible to collapse. As a result, weight-bearing is restricted for 10-12 weeks. Motion is encouraged early. Patients are allowed to return to full activity 12 months after surgery.

Patellofemoral Disorders
The patellofemoral joint is the articulation between the undersurface of the kneecap (patella) and the groove in the front of the femur (trochlea). It is a common source of pain and disability in patients. Patellofemoral issues commonly present as pain in the front of the knee (anterior knee pain). Aggravating factors include stair climbing and standing up from a seated position. Multiple conditions can present with patellofemoral pain, which can make determining optimum treatment difficult. Fortunately, most anterior knee pain responds to conservative management, but specific surgical indications do exist for some conditions. More detailed descriptions of these conditions follow.

Lateral Patellar Compression Syndrome
Lateral patellar compression syndrome (LPCS) is a common condition that presents with anterior knee pain. It is characterized by a tight lateral retinaculum (tissue on the outside of the patella). This tight tissue causes abnormal motion of the patella within the trochlea. This can be exacerbated by other patient factors, such as limb alignment and muscle strength. Patients with LPCS have limited medial (inside) mobility of the patella and may have a patella with excessive lateral tilt.

Conservative management is indicated in all cases of LPCS. Physical therapy is the mainstay of treatment. Quadriceps strengthening, flexibility training, and patellar taping all can be beneficial. A patellar sleeve or brace can also be helpful during athletic activities. A dedicated course of nonoperative treatment needs to be attempted before considering surgical intervention for LPCS.

Lateral Release
The most common surgical intervention for LPCS is a lateral release. This procedure involves surgically dividing the tight lateral retinaculum that is tethering the patella. It is most often done arthroscopically as an outpatient procedure. There is a mild risk of excessive bleeding within the knee after the release. Results for this procedure are good if strict surgical indications are followed. The rehab postoperatively involves minimizing swelling initially, followed by dedicated quadriceps strengthening.

Patellar Instability
Patellar instability occurs when the kneecap slides out of its groove (trochlea) as the knee bends. Most commonly, the patella displaces (dislocates) in a lateral direction (toward the outside). Patellar instability can be described as acute or chronic. Acute patellar dislocations occur when a twisting force is applied to the lower leg. The femur rotates inward while the tibia and the patella rotate outward. This can result in a patellar dislocation.

Chronic patellar instability occurs in patients that have developed specific anatomic risk factors. A wide pelvis, a shallow trochlea, a high-riding patella, knock-knees, flat feet, and underdeveloped thigh musculature are all risk factors for recurrent patellar instability.

The treatment of acute patellar dislocations is typically nonsurgical. A brief period of immobilization (4 weeks) is followed by a dedicated rehabilitation program. Rehab should focus on quadriceps strengthening exercises and flexibility training. The primary surgical indication for an acute patellar dislocation is when a piece of cartilage breaks off of the undersurface of the patella. If that occurs, the treating surgeon will scope the knee and either reattach or remove the broken piece of cartilage.

Patients with chronic patellar instability often have some degree of lower leg malalignment. Rehab can be attempted but is less successful in chronic cases. Multiple procedures have been developed to try and address recurrent patellar dislocations. The most successful operations involve trying to improve the alignment of the extensor mechanism. This allows the knee cap to stay in the trochlea during knee motion.

Proximal and Distal Realignment Procedures
For patients with chronic patellar instability, surgeons try to change the direction the kneecap travels during motion with hopes of eliminating dislocations. These procedures can be quite complicated depending on the amount of correction that the individual patient requires. Some basic surgical principles exist, however, despite the variation in specific techniques.

In most cases of patellar instability, the tissues on the inside of the patella are loose and the tissues on the outside are tight. Also, the alignment of the extensor mechanism is abnormal. The majority of surgical procedures for this condition attempt to correct these three factors. It is not uncommon for patients to spend a day or two in the hospital after surgery.

An arthroscopic lateral release is utilized to divide the tight tissues on the outside of the patella. This has been described previously. Next, in order to change the pull of the extensor mechanism, a realignment procedure is needed. This is reserved

for patients who have stopped growing. Realignment is typically accomplished by performing an osteotomy of the tibial tubercle. The tibial tubercle is the bony prominence on the front of the shin bone where the patellar tendon attaches. An osteotomy involves separating the tubercle from the tibia and shifting it in an inward direction. This requires an open incision and screws are usually placed to hold the shifted piece of bone in position. Lastly, some form of medial (inside) tightening procedure is performed. This usually requires a second incision on the inner portion of the knee. Sutures are utilized to tighten tissues on the inside of the patella that have become loose from multiple dislocations.
The postoperative rehabilitation for a proximal/distal realignment procedure involves a period of protected weight-bearing with crutches to allow the osteotomized bone to heal. A brace is worn to protect the knee for 4-6 weeks. Range of motion exercises are initiated early. Return to sports is permitted 4-6 months after surgery.

A plica is a band of synovium (lining of the inside of the knee) that is a normal remnant of embryologic tissue. Almost all knees have some form of plica, and they are often normal findings seen at the time of arthroscopy. Occasionally, however, patients can have symptomatic plicae. Plical pain is typically located on the inner portion of the knee next to the patella. Sometimes, popping or snapping can be elicited with knee motion.

Symptomatic plicae can be treated conservatively with medications, activity modification, and therapy. Surgical management is reserved for plicae that are resistant to nonoperative treatment. Surgery is performed arthroscopically simply by removing the pathologic tissue with a shaver. Postop rehab is identical to that of basic knee arthroscopic procedures.

Fat Pad Impingement
The anterior fat pad is fatty tissue that is located below the patella and behind the patellar tendon. It serves to provide some extra cushion for the front of the knee. Sometimes, after trauma, this fat pad can become symptomatic. The fatty tissue can become thickened and irritated making it difficult for the patient to straighten their knee.

Treatment for fat pad impingement is usually conservative. Activity modification, rest, ice, and knee padding are helpful. Occasionally, arthroscopic excision is utilized in patients that fail conservative therapies. The abnormal fat pad is removed with an arthroscopic shaver. Postop rehab is identical to that of basic knee arthroscopic procedures.

Extensor Mechanism Disruption
The extensor mechanism consists of all the structures that allow for the leg to be straightened (extended). The quadriceps muscles coalesce into a central tendon that inserts on the top of the patella. The patellar tendon is a band of tissue that connects the bottom of the patella to the tibial tubercle on the shin bone. Both of these tendons can be sites of knee pathology.

Quadriceps and patellar tendon ruptures are somewhat common injuries. Typically, patients who experience this injury fall onto a partially bent knee. When the quadriceps muscle contracts to break the fall, the quadriceps tendon or patellar tendon cannot withstand the force and ruptures. This injury is most common in middle-aged patients who are part-time athletes (weekend warriors). After sustaining a quadriceps or patellar tendon tear, the patient experiences knee pain, swelling, and is unable to straighten the leg from a bent position.

Treatment for quadriceps and patellar tendon ruptures is almost always surgical. The tendon tears off of the bone and it needs to be reattached. This involves an open incision on the front of the knee. The edges of the torn tendon are cleaned up and sewn back to the kneecap with large caliber nonabsorbable suture that is placed through small drill holes in the patella. After surgery, patients are put in a knee brace locked in extension. Patients can walk and bear weight on crutches with the leg in an extended position. Range of motion rehab is started after a few weeks of immobilization to protect the repair.

Expected Outcomes
A wide spectrum of pathology can be treated with knee surgery. Results of surgical intervention vary based on the patient’s individual diagnosis and treatment rendered. Most operative procedures offer good results in most cases. Exceptions always occur. It is important for the patient to have a thorough discussion preoperatively with their treating surgeon so they have a complete understanding of the expected goals and outcomes for their specific condition. Patient compliance and dedication to postoperative rehabilitation are also essential factors to maximize results following knee surgery.

Despite considerable progress in the field of knee surgery, surgical complications still exist. Every operation, as small as it may be, carries a wide range of risks from the most insignificant to the most serious (including fatal complications). Surely, discussing these complications with a patient does not mean that they will occur, but, by the same token, the failure to discuss these potential complications with the patient will not make them disappear. Patients are encouraged to ask their surgeon about potential complications, and the surgeon’s response should be forthcoming. Knee conditions are not life or death situations. Knee surgery pertains to quality of life. Therefore, it is essential for the patient to determine whether surgery is reasonable. To reach such a decision, the patient will use the information provided by the surgeon. The list of potential complications is extensive. Fortunately, complications are usually rare and benign.

The incidence of complications is low compared to the high number of arthroscopic procedures performed yearly. Possible complications include infection, swelling, damage to the tissues in the joint, blood clots in the leg veins (thrombophlebitis), accumulation of blood in the joint (hemarthrosis), blood clots that move to the lung (pulmonary embolus), and injury to the nerves around the joint.

Arthroscopic knee surgery is the most common procedure performed by orthopaedic surgeons. A large number of conditions can be treated successfully with arthroscopic techniques. The specific goals of each procedure vary based on individual diagnosis, but common themes include pain relief and restoration of form and function for patients.



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