Knee pain is the most common musculoskeletal complaint that brings people to their knee pain specialist. With today’s increasingly active society, the number of knee problems is increasing. Knee pain has a wide variety of specific causes and treatments. Some people have injured their knee from a specific incident leading to torn ligaments, meniscus or cartilage. Others have knee pain from overuse injuries such as repetitive stress on the knee joint leading to muscle imbalances around the knee and poor tracking of the kneecap. Another condition that can cause knee pain is arthritis, which comes in many forms. With osteoarthritis, the smooth, gliding surface covering the ends of bones gradually becomes worn and frayed, often resulting in painful bone-on-bone rubbing. Rheumatoid arthritis is a disease in which the synovial membrane becomes thickened and inflamed, producing too much synovial fluid which over time can lead to loss of cartilage and pain. Other forms of arthritis can be due to uric acid crystals, infection, or the effects of medication. Although knee pain is so prevalent, the complexity of the knee and the seemingly infinite number of mechanisms that can cause pain can make it very hard to determine where the pain is coming from. Additionally, the vast strength of the surrounding muscles and ligaments make the knee one of the most stable joints in the body that functions best when it is allowed a normal amount of movement over a long period of time. Paired with the fact that the knee is a weight-bearing joint, the largest in the body, the ability for the knee to experience pain is greatly magnified. Because of this, an injury or imbalance at a higher point in the leg or body can lead to pain in the knee joint itself.
1.1 What is knee pain?
Knee pain may be the result of an injury, such as a ruptured ligament or torn cartilage. Medical conditions including inflammation, obesity, and arthritis could also be contributing factors to knee pain. The complexity of the design of the knee and the fact that it is an active joint can also lead to knee pain. The majority of movement in the knee is hinging motion within the joint. This is created by the articulation of the two ‘condyles’ at the end of the femur (thigh bone) with the flat upper surface of the tibia (shin bone). Articulation between the condyles and the tibia is made smoother by the kneecap, which acts to increase the leverage of the quadriceps muscles (muscles of the front thigh). Between the condyles and the tibia are two pads of cartilage called the ‘menisci’. The menisci act to absorb shock within the joint and prevent wear and tear of the bones. Two ligaments on either side of the knee act as a stabilizing hinge, which often are the site of sprains or tears, a common cause of knee pain. The motion within the knee joint is completed by the action of muscles in the upper leg and lower leg, which act to produce movement and stability of the knee. Overuse of these muscles or impact on the upper or lower leg could be a source of pain in the knee.
1.2 Common causes of knee pain
Gradual onset of pain at the front of the knee can be due to patellofemoral pain or chondromalacia. This is a result of the kneecap (patella) not gliding smoothly over the lower end of the thigh bone (femur). The articular cartilage can be softened and damaged due to the abnormal movement leading to chondromalacia. Patellofemoral pain and chondromalacia may be due to an imbalance or weakness in the thigh muscles, tight lateral restraints, or abnormal alignment of the kneecap. These factors can cause the kneecap to be pulled sideways against the femur. An x-ray or MRI scan would be the next step to identify the cause of the pain. Tilted patella, dysplasia of the trochlea, and tight lateral restraints are other possible causes of patellofemoral pain syndrome. Step-up and drop off the shoes and hiking can lead to a soft tissue injury at the front of the knee. This condition is also commonly known as runner’s knee. Osgood-Schlatter disease is an overuse injury that occurs in growing children and teenagers. It’s an inflammation of the patellar ligament at the tibial tuberosity and is usually due to a growth plate injury. Schlatter’s disease can cause a painful swelling just below the kneecap.
Knee pain is one of the most common complaints at our clinics in Singapore. It can be due to sudden injury, an overuse injury, or an underlying condition such as arthritis. In this section, we will look at some of the more common causes of knee pain. This should help you understand your knee condition. If you have had a recent knee injury, sudden (acute) pain may be due to a simple ligament sprain. PCL and ACL injuries are common in sports like football, rugby, and martial arts. An injury to the meniscus is another common acute knee injury. The meniscus is a rubbery C-shaped disk that acts like a cushion between the shinbone and the thighbone. The primary role of the meniscus is to distribute the weight of the body above it and reduce friction during movement of the knee.
2. The Anatomy of the Knee
– Cruciate ligaments: These are found inside your knee joint. The anterior cruciate ligament runs diagonally in the middle of the knee. It prevents the tibia from sliding out in front of the femur and it also provides rotational stability to the knee. The posterior cruciate ligament is often termed the strongest ligament in the knee. It runs at the back of the knee and prevents the tibia from moving backwards and, in doing so, keeps it in place with the femur. – Collateral ligaments: These are found at the sides of the knee and control the sideways movement of the joint. The medial collateral ligament is on the inside, and the lateral collateral ligament is on the outside. They both prevent the leg from overextending in the knee joint.
The shape of the knee joint does not allow for stability. To prevent dislocation of the joint, the knee relies on a limited range of movement and ligament support. Only the very ends of the thigh and shin bones touch, and they are held together by ligaments. These include:
– Femur: This is the upper leg bone or thigh bone. It is the longest and strongest bone in the body. – Tibia: This is the larger of the two lower leg bones. The top of the tibia is flat and this is where the femur rests. It is often referred to as the shin bone. The tibia absorbs most of the body weight. – Patella: This is the kneecap. It is a small, flat, triangular bone that protects the knee joint and increases the leverage of the quadriceps muscles.
Knees are the largest joint in the human body and are crucial for stability and movement. They are formed by the following:
2.1 Structure and function of the knee joint
Knee pain and difficulty moving the knee can be symptoms of an injury. Clinically, an injury is defined as damage or harm to the body’s tissues that can affect normal activity. Up to 25% of people visit a doctor each year due to knee pain, making it the second most common musculoskeletal complaint. Seventy-five percent of those people are diagnosed with a knee pain condition. Injuries can cause tissue damage that could potentially lead to internal problems. The location of the pain can be a sign as to what internal knee problem an injury has caused. For example, an injury on the meniscus typically causes pain on the inside or outside of the knee. The pain could be sudden and severe or gradual. Most sudden knee pain is a result of an obvious injury that can be diagnosed using an x-ray or MRI. Internal knee problems may be diagnosed despite joint pain being the only obvious symptom. An example of this would be someone feeling a lack of stability in their knee. This could be a sign of a weakened ligament and cause the person to favor the leg by putting more weight on the other leg. This would eventually cause the knee with pain to develop into a condition due to the extra stress now being placed on it.
The knee is the largest joint in the body and is central to almost every move the human body makes. It is a hinge joint, similar to the axle on a door, that allows the leg to extend and bend. The knee is made up of bones, cartilage, synovial lining, ligaments, and tendons, all of which are subject to a variety of stresses. The three bones in the knee are the femur, tibia, and patella. Articular cartilage is a smooth substance that protects the bones and enables them to glide easily over each other. The meniscus is a c-shaped cartilage that acts like a cushion in the knee. Synovial membrane is a lining that releases a sticky fluid that is contained in the joint capsule. The Anterior Cruciate Ligament (ACL) is one of the four main ligaments in the knee that connects the femur to the tibia. The ACL prevents the tibia from moving further forward from the femur. The Posterior Cruciate Ligament (PCL) also connects the femur to the tibia and keeps the tibia from moving too far backwards. The Medial Collateral Ligament (MCL) is a ligament that runs along the inner part of the knee. It provides stability to the inner part of the knee. The Lateral Collateral Ligament (LCL) is on the outer part of the knee. It is much less common to injure either the MCL or LCL than it is the ACL or PCL. These are all key components to understanding knee pain and how the knee works.
2.2 Bones and ligaments in the knee
There is considerable controversy over how to best represent the function of the ACL. Still, it is widely accepted that the ACL resists anterior tibial translation and provides rotational stability to the knee. The ACL is the primary restraint to an anterior translation of the tibia on the femur. The postural orientation of the ACL appeared in a recent in vivo study to change from sagging in knee flexion to becoming straighter in extension, which would mean that the ACL function becomes progressively more important as the knee is extended. Deterioration of the ACL is seen to result in the knee giving out from beneath the person during such activities as twisting or changing direction, with the incidence of osteoarthritis increasing due to the resulting instability.
The knee is a hinge joint that allows flexion and extension but no axial rotation. The knee joint is formed by the articulation of the distal end of the femur bone and the proximal end of the tibia bone. The fibula, though not part of the knee joint itself, is the site of origin of the lateral collateral ligament. The knee is often referred to as a “modified hinge joint” because it can rotate slightly from side to side. The tibiofemoral joint is the primary articulation, where the large weight bearing femoral condyles sit atop the relatively flat tibial plateau. The smaller joint between the femur and patella is called the patellofemoral joint. The back of the patella is shaped to fit the front of the femur and is pulled over the end of the femur by the quadriceps. With knee extension, the patella is pulled slightly upward, and with knee flexion, the patella is pulled slightly downward.
2.3 Muscles and tendons involved in knee movement
The 4 quadriceps muscles act to extend the knee and have a large influence on the forces passing through the knee cap, hence the strength of the quadriceps is an important factor in knee pain and injury. The other two actions at the knee joint; rotation and glide are controlled by the popliteus, a small muscle at the back of the knee. Any forces transmitted through the knee joint, whether they are in normal function or due to injury, are due to the action of one or more of these muscles and will affect the stability of the knee.
In order for flexion and extension to occur at the knee joint, the posterior (back) muscles of the thigh must act on the upper and lower leg. The 3 hamstring muscles start in the thigh and cross the knee joint to attach on the upper part of the tibia, so when they contract they create a force drawing the top end of the tibia backwards and the bottom end forwards. This action is the phase of knee flexion. The hamstring muscles are relatively weaker compared to the quadriceps, which are the large muscles at the front of the thigh.
In terms of movement, the knee joint functions as a hinge between the thigh bone (femur) and the shin bone (tibia), and a gliding joint between the thigh bone (femur) and the knee cap (patella). The joint allows the leg to flex (bend) and extend (straighten) as well as a slight medial (internal) and lateral (external) rotation. These movements are essential to normal walking and are often disrupted when pain or injury occurs in the knee. The ability of the knee to glide and rotate is due to the complex arrangement of muscles surrounding the knee and its 4 bones.
3. Diagnosing Knee Pain
X-rays provide a two-dimensional image of the knee which can be useful in identifying degenerative joint diseases such as osteoarthritis. This is not a test for soft tissue problems however. An MRI (Magnetic Resonance Imaging) scan provides a more detailed picture of the soft tissues (e.g. ligaments, tendons and cartilage) as well as bone. This is a very useful test for many different problems within the knee. A bone scan can be useful for diagnosing stress fractures or bone tumors. It involves the injection of a small amount of radioactive material. The material collects in areas where the bone is healing abnormally. Finally, an arthroscopy involves the insertion of a small camera into the knee joint so that the doctor can look directly at the inside of the joint. This is useful for many different problems, not just when surgery is being considered. It is often the best test for diagnosing the cause of unexplained pain or swelling in the knee.
An accurate diagnosis is important in order to understand the problem and determine the best course of treatment. In some cases, a doctor may be fairly certain of the problem based on the patient’s symptoms and a physical examination. In others, one or more of the following tests may be advised.
Common diagnostic tests for knee pain
One of the first steps in diagnosing knee pain should be consulting a doctor. In knee pain Singapore, this might take the form of a general practitioner or a specialist. In the case of more serious, chronic and recurring knee pain, or knee injury, it is often more beneficial to bypass the general practitioner and consult a knee pain specialist. A specialist is likely to have a higher level of expertise specific to the knee and a greater range of treatment options. This could lead to a more accurate diagnosis and more effective treatment.
Importance of consulting a knee pain specialist
A knee pain specialist is a medical doctor who has undergone additional training to become an expert in treating knee problems. Orthopaedic surgeons and sports medicine doctors are both specialists who can be consulted for knee pain. Patients with complex problems are best managed by a team that may consist of both an orthopaedic surgeon and a sports medicine doctor. These specialists are in the best position to evaluate the patient, whether the problem is chronic or acute. Primary care physicians and physiotherapists are healthcare providers who are capable of managing many routine knee problems, but some may require referral to a knee pain specialist. When this occurs, it is usually because the problem surpasses the routine capabilities of the primary care physician or physiotherapist, rather than a failure on their part. In many cases, seeing a knee pain specialist first may be more efficient for the patient. They are capable of evaluating the problem from its onset, obtaining any necessary tests, providing a diagnosis, and implementing a treatment plan. This may eliminate the need for seeing multiple providers or obtaining unnecessary tests. Choosing the most appropriate healthcare provider will depend on the specific problem and its severity, the patient’s medical history, and the available expertise, but in general, the more complex the problem, the more it will benefit from being evaluated by a knee pain specialist.
Common diagnostic tests for knee pain
X-rays provide images of the dense structures within the body, such as the bones. This method is very useful in helping to identify the cause of the knee pain. It is non-invasive, simple, and vital in aiding the diagnosis and ruling out of certain conditions. An MRI is good for detecting injuries to soft tissue, such as the ACL, meniscus, and ligaments. This is particularly useful for surgical planning. Computerized tomography (CT) is optimal for getting an extremely detailed image of a bony injury. A CT of the knee is typically done if a fracture is suspected or to further assess a bone abnormality seen on X-ray.
It is important to have an open understanding of what your knee problem is all about, as inaccurate diagnosis can result in prolonging the disease and, worst, it can aggravate the problem. Whichever healthcare provider you choose to consult, learning a proper diagnosis for your knee pain is essential. This may involve a thorough medical history, physical examination, and the utilization of diagnostic tests. These are some diagnostic procedures that your specialist may use.
Treatment Options for Knee Pain
It is entirely possible to treat your knee without surgery. The RICE method is good. It stands for rest, ice, compression, and elevation. It may help to see a personal trainer to receive advice on exercises which won’t further damage your knee. Even though you don’t want to exercise your knee, you still need to keep your hamstrings and quadriceps muscles strong. There are certain forms of exercise where you can still keep these muscles strong, without causing any additional stress to your knee joint. This will be advised by a personal trainer, physiotherapist, or specialist doctor. Another excellent form of non-surgical treatment is a steroid injection. This is a powerful anti-inflammatory medication which can be injected directly into your knee joint. It can be very beneficial in the short term. Tablets and exercise can be prescribed for osteoarthritis. This is particularly useful if your knee pain is intermittent. For example, your doctor may suggest taking paracetamol at the maximum dose, or a non-steroidal anti-inflammatory drug such as ibuprofen. They may give you a prescription for an exercise programme designed to strengthen the muscles which support your knee. This could be physiotherapy or specific exercises for chronic knee problems. Sometimes an osteoarthritis sufferer will need orthotics. These are inner soles which are inserted into your shoes. They are specifically designed to re-align and support your foot, thereby reducing the load on your knee joints. They are very useful, but can be quite expensive.
Non-surgical approaches for knee pain relief
The next treatment is the use of nonsteroidal anti-inflammatory drugs (NSAIDs). These include medications such as Ibuprofen, Aspirin, or Aleve and are intended to decrease pain and swelling of an acute injury. The A for aspirin in comparison to the other drugs is also to prevent blood clotting and decrease the risk of pulmonary embolism on long sedentary periods. Medication is most effective when used in combination with the RICE method during the first few days of the injury. The duration of medication use is to be kept at the minimum effective dose to minimize potential side effects and is to be avoided completely with a history of peptic ulcers, gastrointestinal bleeding, or renal dysfunction. With the flair of the recent opioid epidemic, it would be shameful to omit that NSAIDs have become a highly preferred alternative for patients with moderate to severe pain. A recent randomized study showed that the combination of Ibuprofen and Acetaminophen provided more effective pain management than prescribed opioid therapy after a study of emergency room patients with extremity injuries and showed no difference in reported side effects.
The most common of these initial treatment options is the RICE method – rest, ice, compression, and elevation. Rest sometimes requires crutches to avoid weight bearing on the affected joint. The duration of rest is typically prescribed for 24-48 hours after the injury. Ice is meant to decrease pain, spasm, and swelling. Applying ice to the affected joint during the first 48-72 hours is beneficial. There is a recommendation for 20 minutes wraps in a moist towel. There are no true studies determining the length of ice application. Compression and elevation help reduce the swelling. This step is likely to be the least understood. Depending on the knee injury, compression may cause a deep bruise and cause more swelling. In these circumstances, a compression wrap should be worn on site for the initial benefit of reduced swelling from the first two steps. Then compression may be avoided for a few days to avoid irritation on the healing tissue. Elevation is self-explanatory, at a level above the heart, to aid in fluid drainage and prevention of swelling. This has proven to be the most effective on minor knee joint effusions where a significant improvement is shown in a few hours.
Surgical interventions for knee pain management
Autologous chondrocyte implantation (ACI) is another procedure that involves two operations. In the first operation, a sample of healthy articular cartilage is arthroscopically taken and cultured in a laboratory to increase the number of cells. In the second operation, which takes place a few weeks later, the chondral defect is exposed and the new cells are injected beneath a periosteal patch. ACI can be an effective means of gaining pain relief and returning to a normal lifestyle for young individuals with isolated full-thickness cartilage damage, who might otherwise require partial or total joint replacement.
Joint-preserving surgery encompasses a wide group of procedures, each with the aim of providing an alternative to joint replacement by repairing or regenerating articular cartilage and meniscal tissue. One such procedure is microfracture, which stimulates the growth of new fibrocartilage and is effective for small, well-defined areas of full-thickness cartilage loss, usually in young individuals. Another procedure is a chondral paste graft transplant, which is the first choice for repairing local osteochondritis dissecans and has one of the best long-term results and a strong evidence base.
Anatomical realignment osteotomy is a technique used in younger individuals with unicompartmental osteoarthritis. It involves the correction of a bony deformity, often in the varus knee, by removing a wedge of bone from the tibia below the knee. The aim is to shift the weight-bearing axis from the damaged side of the joint to the undamaged side. This technique is often effective at delaying the onset of end-stage osteoarthritis of the whole joint, which might otherwise require joint replacement. High tibial osteotomy is the most common type of osteotomy.
Unloader bracing or an orthotic with a medial thrust is often tried, although the evidence for their efficacy is based on clinical experience rather than randomized controlled trials. Complex or reconstructive surgical procedures are generally only carried out by a surgeon specializing in knee problems, working in a unit with a special interest in knee surgery.
This is the most crucial section for your understanding. Surgical intervention encompasses a wide array of techniques, from the expensive to the less costly. One such technique is arthroscopic surgery, where small knee poke holes are made and an extremely small video camera and surgical tools are inserted through the other holes. This is a less invasive and commonly performed procedure. However, it is important to note that any form of invasive surgery carries risks, complications, and benefits.
Rehabilitation and recovery after knee surgery
Patients can expect to be on crutches for a period of time, usually between two days to 6 weeks post-op, depending on the type of surgery that was performed. Those patients that have had surgery to repair a fracture, or a more extensive type of surgery, can expect to be using crutches for a longer period of time. Initial weight bearing will be limited so as to protect the knee during the early phases of rehabilitation. Full weight bearing with the knee is usually allowed when the quadriceps muscle strength has returned at a near-normal level. Time frames for discontinuation of crutches and weight-bearing status differ greatly depending on the surgeon as well as the type of surgery that was performed. Full return to high-impact activities such as running and jumping will vary from 4 months to a year post-surgery, again depending on the type of surgery that was performed, and may not be possible at all for some individuals.
Rehabilitation and recovery are often as important as the surgery for successful outcomes. Only after regaining thigh muscle strength and knee motion should a patient expect to return to full function. The rehabilitation program initially focuses on restoring motion to the knee and then strengthening the leg muscles. This is done under the guidance of a physiotherapist. It is common for the patient to use a continuous passive motion (CPM) machine in the postoperative period to work on knee motion. This machine helps to place the knee through a range of motion while the patient relaxes.
