Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Knee Fractures in Singapore

The knee is the joint between the femur (thigh bone) and the tibial (lower leg). In front of the knee joint is the patella (kneecap), a bone set in the tendon of the big quadriceps muscle which straightens the leg. Knee fractures are injuries to one or more of these bones close to the knee joint or entering the knee joint.

Many of these injuries heal well and cause no later problems, but breaks that enter a major weight bearing joint like the knee joint are a big concern. If the joint surface is damaged, or if the bone heals with irregularities to the joint surface, wear and tear arthritis of the knee may result. The knee is subjected to various strains due to cutting and pivoting movements and impact injuries. These strains can damage the ligaments and muscles of the knee but they can also cause fractures. Although these fractures may seem quite minor on x-ray they may result in loss of function of the ligaments and/or muscles – the ligament injury itself may be more important than the bony injury.

What structures are most commonly injured?

The knee joint has most of its motion in a single plane, bending and straightening from zero to about 145 degrees. This motion is allowed by the rounded shape of the end of the femur (thigh bone) and the flat shape of the upper end of the tibia (lower leg).

The surfaces of the femur and tibia that touch each other at any point of this movement are covered by smooth joint surface (tibiofemoral joint surface). The bones themselves are smooth but they are also covered with a layer of gristly hard-wearing articular cartilage. Articlular cartilage is softer than bone and does not contain the calcium salts that make bone hard. As a result this part of the joint surface does not show on standard X-rays. On X-ray, it looks as though there is a gap between the bones.

The end of the femur joins the top of the tibia to create the knee joint. Two round knobs called femoral condyles are found on the end of the femur. These condyles rest on the top surface of the tibia. This surface is called the tibial plateau. The outside half (farthest away from the other knee) is called the lateral tibial plateau, and the inside half (closest to the other knee) is called the medial tibial plateau. The patella glides through a special groove formed by the two femoral condyles called the patellofemoral groove.

The smaller bone of the lower leg, the fibula, never really enters the knee joint. It does have a small joint that connects it to the side of the tibia. This joint normally moves very little.

Either or both the tibiofemoral and the patellofemoral joint surfaces can be injured in a knee fracture. Making sure they end up as smooth as possible once the fracture heals is an important consideration.

Surrounding the knee is the joint capsule. The joint capsule is a water tight sac that is made up of ligaments and connective tissue between the ligaments. The joint capsule forms a pocket that is filled with joint fluid (also called synovial fluid). Joint fluid is necessary to lubricate the joint and nourish the articular cartilage.

Ligaments are strong bands of inelastic fibrous tissue that go from one bone to the next. The collateral ligaments limit side-to-side movement of the knee and the cruciate ligaments limit front-to-back motion between the femur and tibia.

Together, the joint capsule and ligaments stabilize the knee and keep abnormal movement from occurring. There is a small amount of rotation but almost no side-to-side or front-to-back motion in the normal knee.

The posterior capsule is tight when the knee is straight, but slack when the knee is flexed. It prevents over-straightening.

When the knee ligaments are normal the knee moves smoothly and feels stable and reliable in all positions. This stability may be lost when the ligaments are injured. If the ligaments are stretched or torn the knee feels unstable. There is often a shifting or opening sensation during knee movement.

During an injury ligaments may be stretched, torn or tear away from their attachment to the bone. When the ligament pulls away from the bone with a fragment of bone attached it creates an avulsion fracture. It is important to realize that ligaments may stretch as well. Even if the avulsion fracture heals back exactly in position the knee can still be unstable. The collateral ligaments and capsule have the capacity to heal and may even tighten up with time, however the cruciate ligaments have very limited healing capacity. If a fracture pattern suggests a ligament injury, that part of the injury may need the most attention.

The mechanism to straighten the knee against gravity is interesting. The quadriceps muscle (sometimes referred to as the quads) is the biggest and strongest muscle in the body and makes up most of the mass of the thigh. If you put your hand on the front of the thigh and straighten or tense the knee you can feel the muscle contract. Most muscles end in a tendon which passes over a joint and attaches to bone.

The quadriceps is so powerful that it would damage the knee joint if the tendon went directly over it. Instead the muscle is attached to the kneecap and the kneecap is attached to the tibia by a strong ligament (the patellar ligament) which passes from the lower tip of the kneecap to a bump of bone in front of the knee at the top of the tibia. When the quads contract the kneecap moves up on the front of the knee and pulls the tibia with it, straightening the knee.

You can feel the patellar ligament tightening and transmitting the force to the shin if you feel just below the tip of the kneecap. When the leg is relaxed this area is soft. When you straighten the knee or lift the leg off the bed the region tightens up and feels like a bar. The pressure of the extension mechanism is transmitted from patella to femur through joint surface so the bone is not damaged – the joint surface is evolved to transmit forces from bone to bone.

As the kneecap tracks in front of the knee it is held in position by ligaments that pass from the sides of the femur to the kneecap. If the kneecap dislocates one or both of these structures is disrupted. Fractures of the kneecap interrupt the mechanism to straighten the knee. The pull of the quadriceps is no longer transmitted through to the tibia so one cannot bear weight on that leg until the fracture is healed. Since most fractures of the kneecap go into the joint it is important that the two parts heal without a step, otherwise there would be a wear problem.

In summary, the anatomy of the knee is complex. Bones, ligaments, muscles and joint surface are all required for normal function. During an injury, any or all of these structures can be damaged. They must all be restored to near normal for the knee to recover full function.

How do fractures of the knee commonly happen?

There is a great variety of patterns of injury to the knee and a great variety of accidents which may cause knee fractures. Motor vehicle accidents (MVA) may cause patellar fractures or fracture dislocations, especially when the flexed knee impacts into the dashboard. MVA may also cause severe supracondylar fractures. Falls from a height would be more likely to cause a tibial plateau fracture as the weight drives the femur into the tibia. Twisting and bending injuries are more common with sports and these can cause any of the avulsion fractures or osteochondral fractures described.

In the elderly supracondylar fractures and plateau fractures are considered fragility fractures. These fractures may have occurred as a result of osteoporosis. In addition to fixing the fracture, measures should be taken to reduce the risk of falling and the degree of osteoporosis in the future.

What types of knee fractures can occcur?

Fractures of the Femur at the Knee

Avulsion Fractures

The medial epicondyle is a small bump of bone on the inner side of the end of the femur (thigh bone). The medial collateral ligament attaches there and passes to the shin bone below the knee. This ligament prevents abnormal inwards movement of the knee. If the knee is forced into an inward bend the ligament either stretches, ruptures or pulls off the medial epicondyle.

This type of avulsion fracture is not very common and may accompany other serious injuries of the knee such as a dislocation. If a fracture of the medial epicondyle is seen the knee will be unstable side-to-side. Instability in other planes such as front-to-back needs to be checked. This fracture normally heals without trouble but the knee may be unstable if the ligament has been stretched.

An avulsion fracture of the lateral epicondyle on the outer side of the end of the femur is slightly more common. This is the point of attachment of the lateral collateral ligament. The bony bump is quite easily felt on the outside of the knee and the ligament may be felt if you sit cross-legged. The tight ligament can then be felt as a tight band passing down to the upper end of the fibula.

This ligament prevents the knee from bending outwards. If an outward force is too strong the ligament may tear or may tear off the lateral epicondyle. This type of avulsion fracture heals well and the ligament component of the injury does not usually cause major long term problems.

Osteochondral Fractures

In some twisting knee injuries the kneecap can dislocate and chip off a portion of the outer joint surface of the femur. These osteochondral fractures involve the joint surface and a small piece of the underlying bone. Osteo means bone and chondral means cartilage, so osteochondral usually refers to something containing both bone and cartilage.

Osteochrondral fractures are significant for several reasons. First, they indicate that the kneecap came out of position and the restraints that prevent dislocation were torn. This means that another dislocation may easily happen. Second, the fragment may be loose in the joint and may get between the weight bearing bones and damage the joint surface. Third, the extent of the damage to the joint surface may be significant even though the bone fragment appears very small on x-ray. The long term result of the injury will be worse if there is a larger area of joint surface damage. Lastly, these injuries are sometimes difficult to diagnose. The bone fragment is so small that it may be difficult to see on x-ray. Special views or CT scans may be needed to make the diagnosis.

In most osteochondral fractures the loose fragment is too small to heal back into position. The usual management is to remove the loose piece to prevent it from damaging the rest of the joint and to treat the dislocation of the kneecap.

Supracondylar Fractures of the Femur

The rounded ends of the femur are called condyles. There is a type of fracture of the lower end of the femur that starts above the condyles and may pass down into the joint. Supra means above, so supracondylar means “above the condyles”.

There is a great deal of variation in the pattern of these fractures. At one extreme is a simple transverse fracture which does not enter the joint. At the other there may be splintering of the bone and multiple fragments including joint surface. The more severe injuries are caused by high energy trauma and may be open fractures. Fractures of the kneecap and tibial plateau may be involved as well. These injuries are amongst the most challenging fractures to treat.

Fractures of the Tibia at the Knee

Avulsion Fractures

Either the anterior or the posterior tibial spine may be pulled off in knee ligament injuries. The anterior spine is the attachment of the anterior cruciate ligament to the tibia. The posterior cruciate ligament attaches to the posterior spine. These avulsion fractures are rare in adults but indicate that there is a serious injury to the ligaments. Even if the fracture fragment is brought back down to its anatomical position and heals in place, the stretched ligament may not be functional.

The Segond fracture is an avulsion fracture of the anterolateral rim of the tibia. It is an indication that the anterior cruciate ligament (ACL) has been ruptured.

A severe outward bending force on the knee may cause an avulsion fracture of the tip of the fibula. It is pulled off by the lateral collateral ligament.

The point of attachment of the patellar ligament is a small raised area of bone called the tibial tubercle. It can be felt in the front of the knee at the top of the tibia. When the quadriceps muscles are contracting and the knee is straightening all the force is applied to the tubercle. If a sudden extra load is added the bone may fail and a piece of the tibial tubercle is pulled off. This disrupts the mechanism to straighten the knee and is a disabling injury. It often requires surgery as the pull of the muscle tends to distract the bone fragment from its correct position and inhibits healing.

Tibial Plateau Fractures

The flat parts of the tibia which form a joint with the femur are called the tibial plateau. On the outside, or lateral side, of the knee is the lateral tibial plateau and on the inside, or medial side, is medial tibial plateau. Compression forces may be too great for this region and the lower end of the femur may be driven into the the tibial plateau on the inner or outer side – or occasionally both.

These are severe and troublesome injuries which damage the weight bearing surfaces of this major joint. The focus of treatment of a tibial plateau fracture is to restore the smoothness of the joint surface as best as possible. Like supracondylar fractures of the femur there is a wide spectrum of tibial plateau fractures ranging from simple injuries which damage one plateau to extensive fractures with many fragments and involvement of the shaft of the tibia.

Fractures of the Kneecap

Avulsion Fractures

If the extensor mechanism is overloaded the muscle can tear off the patella taking small fragments of the bone with it. This can happen with quadriceps rupture which occurs at the upper end of the patella where the thigh muscle attaches to the kneecap. It can also occur at the lower pole of the patella where the patellar ligament begins. In both these situations it is the damage to the muscle mechanism that straightens the knee that is important. The fracture is not usually a major problem. The injury usually requires surgery to repair the extensor mechanism.

Osteochondral Fractures

When the kneecap dislocates to the outer, or lateral, side the inner, or medial, ligaments tear. Sometimes a piece of bone is pulled off from the inner (medial) aspect of the kneecap. More commonly, a piece of the inner side of the kneecap may be chipped off against the outer side of the femur. This piece is referred to as an osteochodral fragment. It contains both bone and articular cartilage and is often floating free in the joint. The key to management is to make the diagnosis, recognize that the kneecap has dislocated and remove the loose fragment from the joint before it damages the joint surfaces.

Transverse Patellar Fractures

A common pattern of fracture of the kneecap is a transverse fracture. This means that the fracture line travels straight across the kneecap from side to side. The pull of the quadriceps is too great for the strength of the bone so it is pulled apart. This can happen when there is a sudden increase in load when you are straightening the knee. A more complex injury can occur as a result of an impact against the kneecap. The kneecap may shatter with this type of force and there may also be extensive crushing damage to the underlying joint surface. High energy trauma may cause an open fracture of the kneecap.

Symptoms

What symptoms do knee fractures cause?

Fractures around the knee cause pain, swelling and loss of function. It is usually impossible to bear weight on the affected side. Moving the knee is painful. If the fracture enters the joint the knee itself swells as blood from the broken bones distends the joint.

During the period of recovery from a knee fracture there is likely to be continuing pain, swelling, purple discoloration (bruising), and pain on moving the joint. Later on, you may find stiffness of the joint to be a problem.

In some injuries, there may be damage to the nerves and blood vessels that travel around the knee. Nerve damage may result in numbness and weakness in the lower leg. Damage to the large popliteal artery that travels behind the knee joint may result in loss of blood flow to the lower leg.

Evaluation

How will my fracture be evaluated?

First aid for fractures of the knee requires splinting the leg from thigh to ankle to make sure the knee is immobilized. Any wound needs to be dressed. The patient should be kept warm and transported to hospital as quickly as possible.

In the Emergency Room the focus will be on treating shock, making the patient comfortable and making sure that the full extent of injury is diagnosed. Examination of the leg will reveal tenderness at the fracture site, swelling, bruising and pain if the part is moved. If there is a fracture going into the joint (intra-articular fracture), the knee will be distended with blood.

It is quite common for the joint to be aspirated and the fluid removed. To aspirate a knee joint, the surgeon will insert a needle into the knee and remove or aspirate the fluid. Fat globules in the blood drawn off in this way is a sign that marrow fat has leaked through a fracture into the joint. Fat globules in the fluid confirms that there is an intraarticular fracture.

Sensation and circulation of the foot will be carefully checked.

The diagnosis is established by x-ray. Multiple x-rays from different angles are taken to provide a clear picture of all the fractures and to look for any loose fragments inside the knee joint. Where the anatomy of the fracture is complex with many fragments it may be helpful to obtain a CT scan. MRI is not commonly used unless the main focus of the injury is a ligament tear.

Most knee fractures require evaluation and treatment from an orthopaedic surgeon. The orthopaedic evaluation includes a full medical history, including previous fractures and any on-going medical problems or allergies. The examination is often not particularly helpful since, by then, the location of the fracture is known. The surgeon will examine the foot and leg to make sure that the nerve supply and blood supply are intact. If further x-ray, CT scan or MR scan tests are required they will be ordered.

Dr Kevin Yip (+65 9724 1219) will then discuss treatment options, the prognosis, the likely outcome and potential complications. A treatment plan will then be formulated and discussed, describing the method of treatment chosen, the length of time in hospital, the amount of time on crutches and full recovery time.

Treatment

What treatments should I consider?

Nonsurgical Treatment

Because of the wide variety of fractures that occur around the knee there are a large number of different treatment options. Traction, cast immobilization and surgery have all been used.

Traction

This method of treating fractures depends on the fact that stretching out the injured part tends to pull the bone fragments into better alignment. When traction is applied, the ligaments and soft tissue between the fragments pull tight and aligns the bone fragments. If you pull a string of beads taut they line up and the same it true for fracture fragments.

Traction is maintained for several weeks until the healing process has advanced to the point where healing bone is beginning to form between the fragments. This new bone is called callus. Callus can be seen on x-ray, so the surgeon depends on the x-rays to determine when the callus is sufficient to hold the bone fragments together. Bone fragments bonded together with callus should be stable and not move out of position. At this point the traction can be removed and the patient mobilized. A cast or special fracture brace is usually needed at this stage and weight-bearing is not permitted until the fracture is consolidated.

Traction is usually applied under an anesthetic. A stainless steel pin is placed through the shin bone below the fracture. The lower part of the leg is supported in a splint and weights are attached to the pin to keep a constant pull on the bone. Traction can be used for supracondylar fractures of the femur or tibial plateau fractures.

Special hinged splints are used so that the knee can bend while the traction is maintained. This is valuable for nutrition of the joint and helps prevent later stiffness of the knee. Although applying traction may require an anesthetic, it is not a major operation. It causes less stress on the system and may be preferable when other medical conditions make surgery more risky.

The primary disadvantage of traction treatment is that the fracture fragments may not return exactly to their normal position. This mal-reduction can be a problem if it leaves the joint surface irregular. Treatment with traction also requires a long time of immobilization in hospital.

Cast Immobilization

For nondisplaced fractures of any part of the knee, immobilization of the knee is an option. This is the normal treatment for most avulsion fractures, unless ligament reconstruction surgery is also needed. The cast is applied from thigh to ankle leaving the foot out of the cast. If the cast treatment is for an nondisplaced supracondylar fracture or a tibial plateau fracture the knee is usually held in 45 degrees flexion inside the cast. Nondisplaced fractures of the kneecap are rare but may be treated in a cast with the knee straight. With cast treatment one can expect to have x-rays done at intervals during the healing period to make sure the fracture does not displace.

A cast is often also applied after a period of traction. The initial cast may be changed at four to six weeks post injury. An x-ray at this stage is used to confirm that the position of the fracture is still acceptable and to assess the progress of healing. A second cast or a removable splint is then applied. If the splint is removable the surgeon may recommend you take it off and do non-weight-bearing exercises to bend and straighten the knee once or twice a day. Weight-bearing is allowed once there are X-ray signs of adequate healing.

Treatment of fractures in a cast seems simple and understandable. No operation is required and most casts can be applied without an anesthetic. But, cast treatment has disadvantages. The fracture fragments may not be accurately reduced or may displace during the healing period leading to malunion. Prolonged immobilization in a cast may lead to stiffness of the knee. The difficulty in recovering range of motion may result in later wear-and-tear changes and arthritis of the joint.

Cast treatment may make full recovery longer because the cast immobilization is continued until healing has occurred. Once healing is adequate to begin physical therapy, the knee is stiff and the muscles of the leg are weak. Recovering normal function then requires a longer period of rehabilitation.

Surgery

The most popular method of surgical treatment of knee fractures in North America is open reduction and internal fixation (ORIF). This means that the fracture site is exposed through an incision in the skin (open), the fracture fragments are moved back into the correct position (reduction) and then held in place by metal implants such as pins, screws and plates (fixation). The fixation devices are left on the bone and the wound is closed.

The intent of this surgery is to hold the bone fragments rigidly in place and allow movement of the joint while the bone is healing. Weight-bearing is not permitted until the bone is healed, otherwise the fixation devices would bend or fail by metal fatigue. There is a great advantage to have the joint move again soon after the surgery. Early motion reduces the risk of stiffness and arthritis of the knee. Motion also shortens the period of recovery. Healing, recovery of movement and strengthening can proceed together.

Arthroscopic Surgery

Treatment of some knee fractures is possible using the minimally invasive procedure of arthroscopy. In this technique a small camera is inserted into the joint and the fragments can be manipulated using the camera to visualize the inside of the knee. This can be used to retrieve and remove a loose osteochondral fracture fragment. If more complicated repair of the ligaments or muscle attachments is required, arthroscopy may be combined with open incisions to allow the surgeon to fix these injuries as well.

Avulsion fractures of the tibial spines may also be reduced and fixed using an arthroscopic technique alone. Certain very simple tibial plateau fractures can also be reduced and fixed using arthroscopic technique. One assumes that this approach will be expanded in the future as techniques are developed to reduce more complex fractures arthroscopically.

Avulsion Fractures

Where the attachment of tendon or ligament has been pulled off it may be necessary to fit the bone fragment back to the exact site it came from in order to restore the normal function of the tendon or ligament. For example, avulsion of the patellar ligament from the tip of the patella or the tibial tubercle would normally be treated by opening up the site of the injury, replacing the fragment in the correct position and fixing it with a small screw. The strain is taken off the repair by passing a wire transversely through the kneecap then circling round to pass through the tibia below the tubercle. This wire then absorbs the pull of the muscle until the fracture fragment has healed in position.

Supracondylar Fractures

If surgery is chosen for treatment of these fractures it can be undertaken by an intramedullary nail or by a plate applied to the outer side of the lower end of the femur.

In the first technique in incision is made into the knee. Any intra-articular fragments are reduced accurately and fixed with pins or screws; this is to ensure that the joint surface is restored to smoothness. Then a rod is passed up into the intact upper part of the bone and fixed with transverse screws. The lower part of the bone is also fixed to the rod; thus all fracture fragments are held immobile and in good position by the metal rod inside them. This technique has the advantage that exposure of the fracture fragments can be quite limited with less disturbance of the blood supply of the bone.

Some surgeons are concerned that the technique enters the knee joint and may cause later damage from small pieces of bone floating in the joint. There is also an issue about entering the knee joint again to remove the rod if that becomes necessary after the fracture heals.

The second method of treating supracondylar fractures involves exposing the bone fragments from the outer side, moving them back into position (reduction) and fixing them by a long metal plate fixed to the bone above and below the fracture. A variation of this technique involves indirect reduction of the fracture fragments with minimal exposure. The plate is slid up under the muscle so that the blood supply is not disturbed.

Tibial Plateau Fractures

Depending on the anatomy of the fracture the inner or the outer side of the upper end of the tibia is exposed. Exposing a fracture means that an incision is made and enough of the tissue surrounding the fracture is moved aside so that the fracture can be seen good enough to repair it. The fracture fragments are then reduced, paying particular attention to the joint surface. It is common for parts of the joint surface to be broken and pushed down inside the bone. This is referred to as a depressed tibial plateau fracture. These fragments need to be lifted up, or elevated, and held in position by plates and screws. The plate extends down on the side of the shin bone to provide fixation above and below the fracture.

Bone graft is often used to add support for the depressed fragments. It is sometimes impossible to restore the smoothness of the joint surface exactly and in other cases there is extensive irreparable damage to the joint surface. In those situations the aim of fracture treatment is to preserve the correct overall shape of the bone so that a later knee replacement can be done.

In some cases, a less invasive technique may be recommended as treatment. This minimally invasive technique for tibial plateau fractures uses a combination of open reduction for the joint surface and an external fixation frame for the rest of the fracture. The frame consists of strong pins passed through the skin and into the bone above and below the fracture. These pins are then attached to a ring system outside the leg. The rings are connected by strong bars and the whole assembly holds the fracture fragments still while healing takes place.

The main advantage of this technique is that there is less exposure and disturbance of the blood supply. Unfortunately, there is a risk of infection of the pin sites and this limits the applicability of this technique.

Patellar Fractures

Operative treatment for displaced fractures of the kneecap is the norm. The fracture is exposed and the fragments brought together accurately. The joint surface is the important consideration and every effort is made to avoid a ridge or step in the joint surface. The position of the fragments is then maintained by passing stainless steel wires through the fragments and reinforcing this with a wire that goes round the pins, often in a figure of 8 fashion.

It is usually not necessary to put a cast on the leg after this operation but weight-bearing is not permitted until the x-ray shows signs of healing. The fracture will pull apart and the pins break if pulled on by the strong quadriceps muscle too early.

Bone Grafting

The amount of damage to the bones at the knee can be severe. In these cases it may be valuable to assist the healing process by adding bone graft. When this is considered necessary, the bone is usually harvested from the rim of the pelvis. A small incision is made above the hip, the pelvic bone is exposed and a piece of bone is removed. The bone graft pieces are shaped to fit and packed into the fracture defect.

Bone graft assists the healing process and supplies some mechanical strength. It is used quite frequently in supracondylar fractures of the femur and in tibial plateau fractures. There is on-going research into substitutes for bone graft to facilitate the healing process and remove the need for the operation to harvest bone graft.

Removal of the Implant

Patients usually ask whether implants to treat fractures will need to be removed later. The answer is: it depends. The pins used in the external frame are always removed once the fracture has started to heal. A choice must be made about removal of other types of hardware. Quite often there are symptoms of aching, cold sensitivity and tenderness which are related to the hardware. If these symptoms warrant it the hardware (metal plates, rods, pins and screws) can be removed.

An operation to remove hardware is often viewed with concern by many patients because of the pain experienced after the initial operation and because of concern about re-fracture. Much of the postoperative pain after the original fracture is from damage to the muscle and other soft tissue in the original injury. This damage is not repeated when the hardware is removed to the post-operative pain is usually much less severe and the operation does not usually require a hospital stay.

Re-fracture after hardware removal in the leg is rare although most surgeons limit sports and other heavy activity for a few weeks as a precaution. The bone does not become significantly weaker once the hardware has been removed.

Some cultures prefer hardware to be removed even if there are no symptoms. There is also a school of thought among orthopaedic surgeons that plates should be removed because they shield the bone from stress. Since bone responds to stress by getting stronger, theoretically this stress shielding might make the bone relatively weak. There is not enough evidence that stress shielding actually causes problems later in life to convince all surgeons to subject their patients to a hardware removal operation when there are no symptoms.

Rehabilitation

What happens as I recover?

The normal time course of fracture healing is measured in months. In the standard situation it takes 6 weeks for new bone formation to be detectable at the fracture site by x-ray. The strength of the healing fracture at this stage is about 50% of normal.

By three months there is good bridging bone across the fracture site and the margins of the fracture look blurred on x-ray as the gap between the fragments is filled in with new bone. The healing fracture has about 80% of normal strength by this stage. It actually take up to 18 months to consolidate the fracture and achieve 100% healing.

Of course, there are variation in this timetable depending on the nature and extent of the fracture. Avulsion fractures that have been fixed in position generally recover more quickly and fractures with a large number of fragments take longer. The surgeon, or the doctor following up the healing process will make decisions about weight bearing, exercise and return to heavier activity based on symptoms, X-ray appearance and the strength of the muscles.

As a general guide one might expect to be on crutches for six weeks putting no weight through the injured knee. Then, if the X-ray shows signs of healing, some partial weight-bearing can be permitted, still using crutches. If cast treatment is being used the cast is often changed at this time. A removable brace may be used instead of a cast. Full weight bearing and a vigorous rehabilitation program may be started at three months with return to work at four to six months depending on how heavy your work is.

It should be emphasized that this timetable is a general guide and may not apply to your individual case.

Most knee fractures require physical therapy to make a full recovery. Because the joint is injured and often has to be held still for a time you may require help getting it to move again through the full range. The period of immobilization and limited weight-bearing also results in wasting of the muscles so the next stage is recovery of strength.

The final stage in recovery of full function is occupational and sports rehabilitation so that you have the endurance to return to work and sports at your previous level. This may be a gradual process.

To a great extent the outcome of a knee fracture is determined at the moment of injury. If the fracture is a straightforward transverse fracture of the kneecap with minimal damage to the joint and a configuration which lends itself to anatomical reduction and secure fixation one can expect prolonged healing but eventual recovery to near normal and a good long term outlook. By contrast, if there is extensive damage to the joint surface, multiple fragments and an unstable situation the chances of a normal knee after recovery are much lower. The treatment and rehabilitation plan may affect the outcome – the intent being to give you the best possible chance – but the extent of the injury is the key factor in the end result.

Complications

What are the potential complications of this fracture?

Both the injury and its treatment may have features that complicate recovery. The general complications of fractures are described in more detail in Patient’s Guide to Fractures. These include fat embolism, blood clots, neuro-vascular injury, compartment syndrome, nonunion and malunion. Here we will discuss the complications that are particularly related to knee fractures.

Infection

After an open fracture or surgery the skin, the body’s first line of defense against infection is breached. Open fractures must be thoroughly cleansed and all dead and contaminated tissue removed. Antibiotics are given by intravenous injection. The risk of infection after this treatment varies according to the severity of the injury from 5% to 30% for severely contaminated wounds with compromised blood supply. The risk of infection in the surgical site after a fracture operation is about 2%.

In the case of knee fractures infection may involve the knee joint and this can cause major consequences. Unlike bone the joint surface does not re-grow. If the natural joint surface is damaged by infection that damage is permanent. Special precautions such as drainage are often taken to make sure that pus does not build up under pressure in the knee joint.

The signs of infection in a wound include increasing pain and tenderness. The wound margins are red and the wound may drain pus. The complication will be treated aggressively with further surgery to open up the wound and remove infected tissue, irrigation of the joint and drainage. In some situations an infected wound will be packed with beads containing antibiotics to create a high local concentration of the drug.

The fixation usually remains in place; an infected nonunion is even more of a problem. In most cases this treatment is successful in suppressing or eliminating the infection and allowing the fracture to heal. Once it has healed the fixation can be removed and this usually results in complete healing of the infection. In a small proportion of cases infection may persist and flare up again in the future.

Post traumatic osteoarthritis

If the joint surface is damaged, crushed or fragmented by the injury, full recovery of a smooth normal joint cannot be expected. Unlike bone, joint surface does not re-grow to fill in any gaps caused by the injury. In some fractures it may prove impossible to move all the fracture fragments back into place and keep them there until healing has occurred.

Irregularity of the joint or damage to the surface will cause increased wear-and-tear arthritis of the knee. This post traumatic osteoarthritis may develop quickly or can develop years or decades after the fracture. The symptoms are aching pain, swelling of the joint and loss of the full range of movement. The joint margins are tender and there may be a grinding sensation in the knee. One side of the knee may wear down faster causing angular deformity of the knee and a sensation of laxity.

The first line of treatment of osteoarthritis of the knee joint is medication to reduce the symptoms and allow you to function fully. Sometimes braces are used to shift weight-bearing from the most injured part of the joint. For end-stage post traumatic osteoarthritis, a total knee replacement is a successful treatment.

Summary

There are a number of different fracture patterns around the knee. The common theme of management is to obtain rapid healing of the fracture and recovery of knee function. Because of the importance of a smooth joint and the restoration of normal ligament and muscle function, surgery is often undertaken to make sure everything is fixed back in the correct position. The long term outlook is good for most fractures, but those injuries that severely damage the joint surfaces can be expected to result in post traumatic osteoarthritis. If you have a fracture, do call us immediately after the accident at (+65) 9724 1219 (24 hrs) as the condition would be more susceptible to treatment.

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