About Knee Arthroscopy

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The origin of the word arthroscopy comes from the Greek word ¨arthros¨ which means joint and ¨scopein¨ to look. Today, arthroscopy is a refined surgical technique that allows direct visualization of the inside of a joint using a small camera connected to a monitor. Its first function is diagnostic, because it allows the inside of a joint (knee, shoulder, hip, etc.) to be examined directly. It is considered the gold standard test with the greatest diagnostic value compared to any complementary test such as an MRI. In some limited patients, an exploratory arthroscopy may be performed when there is no clear diagnosis for a problem. The second and most important function of arthroscopy is to repair the injured tissues of the joint according to the presenting pathology (meniscal, cartilage, ligaments, etc.). Its benefits are that it is a less invasive test than open surgery and in general with a lower complication rate. Depending on the joint to be studied cameras of different diameters and lengths are used. The camera is connected to a light source and a monitor similar to a television and the whole team views the the procedure and joint from the inside. The camera is introduced through a small incision (called a portal) in a precise anatomical place using a special cannula. Through the same cannula, a saline solution is introduced under pressure to expand the joint. This allows visualization within the joint and minimizes bleeding through the arthroscopy cannulas

Knee Arthroscopy

Arthroscopic knee surgery involves inserting a 6mm camera into the knee through a small incision (anterolateral portal) next to the patellar tendon. With the camera, a tour of the knee is undertaken visualizing the synovium, cartilage, menisci and ligaments and their dynamic functional relationships. A complementary anteromedial portal is always made also next to the patellar tendon to introduce special instruments that allow the pathology to be identified and treated during surgery. Other accessory portals used are superolateral and posteromedial portals etc depending on the pathology. The most common instruments to explore tissues are hook probes, biters, graspers, scissors, mini-drills to remodel the injured tissues,etc. Electrocautery and thermocoagulation probes are also used for hemostasis (to stop bleeding), remodelling and removal of inflamed (synovitis) or injured tissue in the joint. Upon completion of the surgery, the saline solution is drained from the knee, the incisions are closed, and a dressing is applied. Depending on the initial pathology and the surgery performed, the bulkiness and compression of these bandages and dressings will vary (meniscal resection is not the same as ligament repair).

In almost all cases surgery is performed under regional (spinal) anesthesia, which leaves the area to be operated on numb, but leaves the patient awake and able to respond. This technique is much more beneficial for post-operative pain control and also reduces rates of complications such as infection and thrombosis and subsequently benefit the patient’s recovery. Most arthroscopic procedures are minor surgeries and are performed on an outpatient basis (the patient can go home the same day as the operation).

Indications

Meniscal Pathology

The menisci are a natural padding of fibrocartilage between the femur and tibia on the inside and outside of the knee and form an elastic cushion-like lining. They have a ¨C¨ shape and are called the medial and lateral meniscus. They are strong stabilizing and shock absorbing structures that help the joint distribute weight evenly while allowing sliding smoothly in different directions. There is a lot of current literature confirming that the meniscus is an essential structure in the biomechanics of the knee and that as surgeons we should avoid or delay resecting or removing part of the meniscus, which is better for the long-term function of the knee. However, if it is the main pain generator in the knee after conservative management it may require partial removal.

In the healthy knee of a young person, meniscal injuries present as sudden (acute) tears related to contact sports with sudden changes in direction, twisting and pivoting motions. As young patients have optimal tissue quality and blood supply treatment can be conservative depending on the location and size of the injury. Initial treatment of a minor meniscal sprain or tear follows a basic formula: rest, ice, compression, and elevation, combined with anti-inflammatory pain medications. This conservative management may be all that is needed in the majority of cases. If the knee is stable (does not have an associated ligament injury) it does not require associated immobilization. The outer or peripheral edges of the meniscus (the red zone) have good blood supply giving this part of the meniscus potential to repair itself with conservative management. Surgery is indicated for large (bucket handle) tears and especially when there is a portion of the meniscus which is loose which can cause locking, pain and further damage to the knee cartilage.

Large, displaced tears require a meniscal suture to repair the damaged meniscus. This is the treatment of choice in an acute injury (generally less than six weeks of evolution) in a young patient. Surgical implants and instrumentation have evolved tremendously to perform these repairs safely and less invasively. However, recovery after meniscal repair surgery is longer and requires the use of crutches and braces for about six weeks generally. The final decision to repair or resect the meniscus is taken intraoperatively during surgery depending mainly on the site and type of injury and the time from injury.

In older people meniscal and cartilage tissue quality (collagen, elastin etc.) and their blood supply are poorer from the natural passage of time (especially after the age of 40). Injuries can occur without any previous trauma or injury. Over years the cartilage, menisci and ligaments weaken and wear out and can generate a degenerative tear that causes pain for some time. For the most part, these injuries can be alleviated by conservative management such as intra-articular joint injections, physiotherapy with muscle strengthening exercises and weight loss. Currently, many studies have demonstrated the benefit of biological treatments to complement the treatment and regeneration in these injuries using platelet - derived growth factors or pluripotential stem cells. Arthroscopy remains an option when conservative treatment fails, and knee pain persists. Therefore, the prognosis and treatment of a degenerative meniscal injury is different from an acute rupture in a young person and the treatment plan must be understood and agreed upon with each patient.

Ligament Injuries

In young patients and athletes who perform high-demand and high-impact activities, meniscal injuries can occur in combination with other intra-articular lesions such as ligament tears (typically anterior cruciate) or cartilage (osteochondral) injuries etc. The degree to which a joint damaged is dependent on the severity (energy) of the initial injury and this influences the final prognosis. Serious injuries that affect many important structures will likely have poorer long-term outcomes.

The anterior and posterior cruciate ligaments, and the medial and lateral collateral ligaments, are the main stabilizers of the knee. Posterior cruciate ligament injuries are less common and rarely require surgery. Injuries to the collateral ligaments, and especially the medial collateral ligament, are more frequent, but their treatment is mostly conservative and do not require surgery. This ligament commonly heals in about six weeks by rest, immobilization with braces / splints, and non-weight bearing with crutches. Injury of the anterior cruciate ligament is frequent in contact and high demand sports and the problem its tear creates is the loss of antero-posterior stability of the knee. Surgery with ligament reconstruction is indicated in patients with residual instability (giving way) of the knee and in those who realize high-demand sports or work activity. Chronic knee instability can result in associated injuries to the meniscus and cartilage that are not initially present through chronic subluxation (giving way) of the knee.

Reconstruction of the anterior cruciate ligament restores the anteroposterior stability of the knee and is undertaken with graft tissue. The two commonly used grafts are the hamstring muscle or patellar tendons from the same patient (autografts) or from a cadaver donor (allograft). There are minimal clinical differences between using either the hamstring or the patellar tendon and the decision of which graft is used is generally made by the surgeon who is most familiar with one technique. The advantage of using a donor’s allograft is that it produces less morbidity (injury) to the knee that has already suffered from an initial trauma y and also facilitates postoperative recovery. However, it does have a slightly higher rate of ligament re-rupture (failure) and risk of infection than when using a patient's own tendon graft. 

Cartilage (Osteochondral ) Injuries

Cartilage is a noble body tissue with little blood supply (vascularization) and capacity for regeneration after a person reaches maturity. An injury that affects the cartilage layer can trigger osteoarthritis depending on the size and location of the injury. There are different cartilage regeneration techniques that vary depending on the age of the patient and location of the injury.

With constant medical development there are different types of cartilage regeneration techniques which have improved long-term results after these injuries. These range from microfractures (punching small holes at the bone-cartilage interval to revive it), to grafts of cartilage and bone impacted into the defects and different types of biological protein and collagen gels that stimulate cartilage regeneration. Supplementing these techniques with biological treatments of stem cells or platelet-derived growth factors that have improved the outcome of these injuries significantly in recent years.

Risks associated with arthroscopy

The risks involved in any procedure with anesthesia are allergic general or local reactions to medications, respiratory problems, etc. The risks involved in any surgical procedure include bleeding, infection and thrombosis. Risks specific to arthroscopy include bleeding into the joint (hemarthrosis), damage to the cartilage, menisci, or ligaments of the knee, failure of pain relief, stiffness in the knee and postoperative hypersensitivity pain syndrome (dystrophia) etc. Less common complication may be nerve or vessel injury, fractures or persistent instability.

Expectations after surgery

Arthroscopy reduces the rate of postoperative complications such as pain, stiffness, bleeding and length of hospital stay (if required) and recovery time compared to open surgery. Expectations vary widely when surgery is recommended and depend on the profession and demand of the patient on the joint and outcomes are related to the severity of the initial injury.

In general, surgery performed for a small meniscal tear or intra-articular loose body without any other associated problems (osteoarthritis or arthritis) present minimal complications and most patients can expect a full recovery. The presence of arthritis or joint degeneration (wear and tear) in the knee substantially reduces the outcomes of arthroscopy. In this setting up to 30% of these patients do not improve (with a small percentage of patients that get worse after surgery). Arthroscopic resection of synovial tissue (lining of the joint), or arthroscopic synovectomy, can be of great help in patients who have rheumatoid arthritis.

Arthroscopic surgery performed for meniscal repair, reconstruction of the knee ligament or cartilage injuries are more complicated with a prolonged recovery period and have more variable results depending on the initial diagnosis and injury severity.

Convalescence and immediate postoperative

In arthroscopy with meniscal debridement (partial meniscectomy) recovery is usually rapid in about 2-3 weeks. The patient requires a pair of crutches will be required for 7-14 days to avoid weight and pressure on the knee joint until the effusion (saline and hematoma) from the knee reabsorbs. The level of pain is mild to moderate and is controlled with mild analgesics and anti-inflammatory medication in the postoperative period. Like most interventions on the lower limb, blood thinners are used for between 3 and 6 weeks to avoid the risk of deep vein thrombosis or embolism of the operated leg. Patients are discharged from hospital on crutches but walking independently at the time of discharge. It is important to acquire the crutches before the surgery. The patient is discharged with a compression dressing to immobilize the limb and reduce the swelling of the knee for the first few days until the first control visit. In more complicated procedures such as anterior cruciate ligament repair etc, the patient will be able to walk but with partial weight bearing on the operated leg for a few weeks. Full recovery can last a vary between 6 and 12 weeks for normal independent walking but it may take up to six months for return to sports and high demand activities.

Dr. Aamer Malik

Departamento of Orthopedic Surgery and Traumatology

Hospital Universitari Sagrat Cor.