Osteoarthritis occurs at the joint. It is a degenerative process that affects the hyaline articular cartilage and the subchondral bone. This will finally lead to sclerosis of the bone just below the cartilage and the formation of marginal osteophytes. The synovium and the joint capsule can also thicken. Ultimately, it will result in the damage or destruction of the joint. Osteoarthritis usually affects the knee, hands, spine, and hip.
The knee pain could be due to many causes. An acute injury to the knee can lead to internal derangement of the joint, which may need an operation to rectify it. Some may have pain because of systemic diseases like gout or pseudogout. However, the most common cause of knee pain, especially in the elderly, is osteoarthritis. It has been reported that almost 600,000 people in Singapore will have osteoarthritis by the year 2016. This is a massive increase from the 400,200 in the year 2000.
Knee pain is one of the most common musculoskeletal pains that has an increasing incidence with age. This is a condition that could lead to functional impairment of an individual, be it difficulty in walking, climbing stairs, or even transferring from a chair. Many may find their work affected, and some may end up giving up their job just because of the knee pain. This can result in significant economic and social burden to an individual and society as a whole.
Understanding Knee Pain
Knee pain occurs in people of all ages and the cause of the knee pain can be varied. The pain can develop from overuse of the knee, direct blunt trauma to the knee, or from underlying conditions such as osteoarthritis. The pain from these conditions can be from the inflammation caused by the conditions to the degradation of the structures in the knee’s anatomy. Overuse of the knee can cause pain by damaging the soft tissue or from stressing the bone. This can lead to inflammation within the soft tissue and can cause pain with movement of the knee. Stress to the bone can cause a stress fracture which is a very small break in the bone. This can cause pain and discomfort when putting weight on the affected leg. Osteoarthritis (OA) is a condition where the cartilage in the knee gradually wears away. This can be from age-related wear (primary OA) or from a specific condition or repeated injury to the knee (secondary OA). As the cartilage wears away, it becomes frayed and rough and the protective space between the bones decreases. This can lead to bone spurs being formed, and bits of cartilage can break off and become a loose body. All these factors can cause pain and difficulty moving the knee.
Causes of Knee Pain
Finally, rheumatoid arthritis is a chronic systemic disease that affects many tissues and may cause deformities. This type of arthritis can affect people of all ages, including children, and cause joint destruction and deformity.
Arthritis means inflammation of one or more joints. It causes pain, swelling, and stiffness. Osteoarthritis is the type of arthritis that is most likely to affect the knee. It is a degenerative condition and is the result of the cartilage within the knee joint breaking down and wearing away. This essentially means the shock absorber is gradually being destroyed. When this happens, there is more stress on the bones within the joint and the bones under the cartilage may thicken and change shape.
All these injuries, if treated properly, usually with rest and physiotherapy, should heal over time and the knee will be pain-free. However, if these injuries are not properly diagnosed or not treated correctly, extra stress can be put on the knee and cause chronic pain. This may lead to the injury being longstanding and at an increased risk of it getting worse, due to the change of movement in order to avoid pain in the knee. This could eventually lead to arthritis.
Sudden injury: An example of a sudden injury that can cause knee pain is a meniscus tear. This is a tear in the main shock absorber of the knee, or in simple terms, the cartilage. This can be very painful and can make the knee catch or lock. Another example is an ACL injury. This is a tear in the anterior cruciate ligament. This is a common sports injury that occurs when the knee is twisted the wrong way. Overstretching the ACL can cause it to tear or even rupture. This injury can cause severe pain and can cause the knee to feel unstable.
Knee pain can be caused by a sudden injury, an overuse injury, or by an underlying condition, such as arthritis.
Symptoms of Knee Pain
Pain is the most frequent symptom from which knee patients seek medical help, and it is often the pain that is most debilitating and the one that most affects quality of life. Pain may occur acutely following an injury, or may come on gradually often as the result of an unrecognized injury or malalignment. Jarring pains, that feel as if something is moving out of place within the knee and catching, suggest a loose body. Pain located on the sides of the knee is frequently associated with an injury to the meniscus or collateral ligaments. If pain is located at the front and center of the knee around the kneecap, then it may be due to problems with the patellofemoral joint. This commonly occurs during walking down hills or down stairs, and also with sitting with the knees bent for prolonged periods. Activity-related pain, occurring on walking and relieved by rest, is most frequently seen in osteoarthritis. In more severe cases of arthritis, the pain may be present at rest and disturb sleep. Locking and giving way are symptoms that suggest that something is moving abnormally within the knee, and may be associated with pain and/or swelling. Locking is often the result of a meniscal tear, where a fragment of torn cartilage becomes lodged within the knee, obstructing normal movement, and preventing full extension. The sensation of giving way is the feeling that the knee is about to buckle and not support the body. It is a symptom of knee instability and may be caused by ligament injury or certain knee deformities. Both locking and giving way greatly affect a patient’s function and may limit participation in everyday activities and certain sports. Swelling, like pain, may occur acutely following an injury, or gradually due to an underlying condition. There are many causes of knee swelling and it often indicates an intra-articular pathology. This can be demonstrated by aspiration of the joint, a procedure where fluid is withdrawn from the knee using a needle. By examining the aspirated fluid and in some cases injecting a small amount of local anesthetic or steroid into the knee, this can be both diagnostic and therapeutic.
Diagnosis and Treatment Options
Non-surgical treatment is always considered first. This may involve a change in activity to prevent the progression of the knee problem. Physiotherapist-directed exercises may improve the strength and function of the knee and may be supervised or unsupervised. Weight loss can be an important factor in patients with knee pain, especially those with osteoarthritis, as the extra weight puts additional load on the knee joint. A study from America noted that a reduction in body fat at all levels of BMI resulted in a decreased incidence of knee pain. Medications are often prescribed for knee pain, and the specific type will depend on the diagnosis and severity of the pain. This will be considered in the next section of this article.
The cause of the knee pain will often determine whether the treatment should be surgical or nonsurgical. However, there are always exceptions, particularly where chronic pain has not improved with nonsurgical treatment. The final decision on whether to proceed with surgery is always the patient’s. The surgeon can only advise on the expected outcome and possible risks of the various treatment options.
The diagnosis will usually start with a detailed history of the problem, followed by a physical examination of the knee. Sometimes, examination of other parts of the body, for example, the back or hips, may be required to determine the cause of the pain. Investigations in the form of imaging, such as X-rays, MRI, or ultrasound, are often required to confirm a diagnosis. Needle aspiration of the knee joint, where a small sample of fluid is taken and sent to the laboratory for analysis, is a simple and useful test for acute knee pain. Blood tests are often done to determine whether there is any systemic cause of the knee pain, for example, crystal-induced arthritis or infection.
Knee pain is a common problem with many possible causes. It can originate from any of the knee joint components, including the cartilage, bones, ligaments, and tendons. It is a symptom of an underlying condition, and the cause may be acute or chronic.
Medical Evaluation
An examination is aimed to determine whether the symptoms are coming from osteoarthritis and to characterize its impact on function. This functional assessment is important for setting realistic patient expectations during the process of consultation and treatment planning. An accurate assessment of the mechanical axis should be made to guide treatment, particularly if there are preexisting plans for surgical intervention. The examination should also look for any factors that may increase the risk of disease progression. For example, instability or a meniscal tear in a knee with established mild tibiofemoral osteoarthritis. These factors may be treatable and prevent early joint replacement in the future. Contractures or muscle wasting in certain muscle groups from chronic disuse will guide a different approach to nonsurgical treatments. For example, a patient with advanced arthritis but good muscle strength may benefit from joint replacement compared to a patient with poor muscle strength who may benefit from strengthening exercises and gait aids.
A detailed history is crucial to properly diagnose and manage knee osteoarthritis. The knee pain doctor Singapore may ask about the nature of pain, previous injuries/surgeries, the impact on function, and an accurate description of the location and nature of symptoms. Alleviating and aggravating factors should be noted, as well as the effect on function. The patient’s occupation, recreational, and social activities also provide key information. These clues will help differentiate osteoarthritis from other knee conditions. It may also define the most restricting symptomatic area to guide localized treatments. In some cases, the knee pain is from referred pain from the hip or back, a good history will also provide answers in this situation.
The medical history and physical examination will provide objective criteria to assist in grading the severity of the disease process and which treatments are likely to be beneficial. This will allow a better understanding of the patient’s timeline and may predict a likely functional outcome.
Non-surgical Treatments
It has been suggested that for every flight of stairs climbed, there is an increase in load on the knee equal to 3-4 times the person’s body weight for each step. This is where the idea of using walking aids becomes very valuable. In considering that 1 pound of weight loss eliminates 4 pounds of load to the knee, for a patient with a 20-pound weight loss, there would be an 80-pound reduction in load with each step. Unfortunately, the correlation has not been made to determine the lower limit of weight loss necessary before the impact on symptoms and function can be truly significant.
Weight loss is also in a league of its own for symptom relief. There are studies that have shown for every pound lost, there is a fourfold decrease in load exerted on the knee for each step. This leads to a significant reduction of symptoms. Weight loss is most effective when combined with exercise. Unfortunately, the patient with significant pain and functional limitation has difficulty with certain types of exercise. Up to 40% of the force generated across the knee joint occurs during stair climbing and it is difficult to avoid certain types of activities such as lifting and lowering.
One of the more recent medical recommendations for alleviating pain, correcting deformity, and increasing mobility in a patient diagnosed with osteoarthritis in the knee is to avoid high-impact, high-intensity activities. It is generally a change from the individual’s previous activity level, but studies have shown that activity modification is helpful in relieving symptoms and improving function. It also has the least cost, risk of added symptoms, and potential for self-management.
Surgical Interventions
This is the biggest decision when considering knee surgery. There are various types of knee surgery, the most common being a knee arthroscopy. This is a ‘keyhole’ surgery, which is minimally invasive. It is often used to both confirm a diagnosis and treat a problem. The benefits are that it is only a day surgery procedure, and rehabilitation is quite quick. It is effective in treating problems such as a meniscal tear, mild arthritis, removal of loose bodies, and synovitis. Another form of knee surgery is a partial knee replacement. This is indicated for people who have arthritis confined to one compartment of the knee. It is indicated as it is shown to have better results and less post-operative pain, and is a better cost-effective treatment compared to other interventions for arthritis. However, this option does pose various complex risks and benefits and is best discussed with your orthopedic surgeon. The most common form of knee surgery is a total knee replacement. This is indicated for end-stage arthritis, when changes in the joint are causing daily pain which is not helped by other treatments. This surgery has been shown to greatly improve a patient’s quality of life and their ability to get around. However, it is a major surgery and is best to be avoided for as long as possible due to the expected 10-15 year lifespan of the prosthesis, and the complications that can arise from the surgery and rehabilitation.
Rehabilitation Roadmap
Prehabilitation
Other goals of prehabilitation include reduction of the inflammatory process in the knee joint, improvement to functional and psychological status, and finally, educating the patient about what to expect postoperatively. This can provide a baseline to which the patient can compare improvements and will hopefully lessen unrealistic expectations of instant recovery. A recent article suggests that education of patients with osteoarthritis about the disease process and what contributes to pain and dysfunction can assist in long-term changes to self-management and preservation of an active lifestyle. This may be translated into increased compliance with prehabilitation exercise and lifestyle changes, although compliance to exercise is still a common issue in patients with osteoarthritis.
Prehabilitation aims to “condition or prepare” an individual for an upcoming surgery. Evidence of the effectiveness of prehabilitation in orthopaedics is still not strong; however, it is believed that addressing strength and range of motion deficits before surgery can prevent further losses in these areas during the postoperative phase. Recovery of strength is known to be prolonged and unsuccessful in some individuals post total knee arthroplasty; therefore, addressing strength deficits before surgery is crucial.
Postoperative Rehabilitation
Normal tissues follow a typical pattern of healing. The inflammatory phase, which begins at the time of injury and lasts up to one week, is characterized by pain, swelling, redness, and heat. Neutrophils and macrophages influx the injury site and secrete proteolytic enzymes to remove devitalized tissue and bacteria. The next phase, called the proliferation phase, involves macrophages and fibroblasts secreting substances like cytokines and growth factors that cause extracellular matrix (ECM) and stable structural collagen formation. This phase generally lasts 2-6 weeks. The final phase is called remodeling and has an expected duration of 2-4 months and in the case of ligaments, can last up to 1 year. During this time, there is a gradual change in type III collagen to type I, decreased cellularity, and overall improved tissue strength. A basic understanding of these concepts can provide a patient with reasonable expectations for his rehabilitation.
A general advice is to avoid high impact activities for 2-3 months, and low impact translation exercises should be postponed for at least 6-8 weeks. Straight line treadmill walking can typically begin early for cardiovascular benefit. A discussion with the surgeon regarding optimal time to begin impact activities, cutting, and pivoting is warranted. A patient who undergoes a straightforward articular cartilage procedure with no other pathology found during knee arthroscopy can focus on a simple rehabilitation template. In contrast, a collegiate soccer player who undergoes an extensive multiligament knee reconstruction will require a complex and detailed rehabilitation program. Despite the differences in these 2 rehabilitation templates, an understanding of the normal progress of body tissue and the basic science behind regeneration are universal for all patients.
Physical Therapy Techniques
At last, it is important to assess the level of function of each patient and tailor the exercise program to their needs. For some, it may be an exercise program aimed to help them lose weight and thus reduce the load on the knee joint, and for others, it may be an intensive agility program to help athletes return to competitive sports. Efficacy of exercise therapy in people with knee OA has been proven in literature, but compliance to exercise programs is often low and it is difficult to motivate people to continue exercising. Thus, it is important to find an exercise program that is enjoyable, challenging, and sustainable for each individual.
High resistance isotonic strength training on exercise machines is probably the most effective way to improve muscle strength around the knee joint. This form of exercise can create dramatic gains in muscle strength, it can be finely adjusted to provide optimal loading for the muscles, and machines are often designed with cams and other features to help minimize joint loads. A well-rounded strengthening program for people with knee OA may also include more global lower extremity strengthening with emphasis on the hip abductors and external rotator muscle groups. Although no specific hip muscle weakness has been linked to knee OA, weakness in these muscle groups has been associated with poor mechanics and increased forces on the knee joint during weight-bearing activities. This may, in turn, affect the progression of knee OA.
Static exercises that isolate the quadriceps and hamstrings muscles such as the straight leg raise or leg curl have traditionally been the focus of strengthening programs. More recently, open chain strengthening exercises have been shown to effectively strengthen the quadriceps with minimal effect on disease progression or symptoms. The leg extension exercise, in which the foot is not in contact with a resistance throughout the exercise, is an example of an open chain exercise. However, open chain exercises have been shown to increase joint forces through the knee and may not be ideal for people with knee OA.
Strengthening exercises are the cornerstone of a well-rounded exercise program for knee OA. The muscles around the knee act as shock absorbers for forces transmitted from the ground reaction force through the joint during weight-bearing activities. People with weak quadriceps and hamstrings muscles are more likely to develop knee OA, and weakness in these muscle groups has been associated with progression of the disease. Since these muscle groups are so important in protecting the knee joint, it is crucial that people with knee OA learn how to strengthen them effectively.
Physical therapy plays a crucial part in the treatment of knee osteoarthritis and is a long-term solution in trying to help point sufferers in the right direction in relation to management of their symptoms and to build a life with the ability to do the things they want to do. Exercise therapy is a vital component of physical therapy for knee OA that has been shown to be effective in reducing pain and improving function. There are several types of exercise therapy, each with specific considerations related to knee OA.
Pain Management Strategies
Pain management strategies are an important aspect of managing arthritis and can come in many different forms. Pharmacological intervention is a common method of pain control, the foremost is paracetamol, and therefore its place in arthritis treatment. Guidelines currently suggest giving regular paracetamol to all individuals with knee and/or hip OA, unless there are contraindications. Non-steroidal anti-inflammatory drugs (NSAIDs) are also frequently used for pain relief. They have been shown to be more effective than paracetamol for managing pain in OA. However, their gastrointestinal, renal, and cardiovascular effects are well-documented, and it is suggested that they be used at the lowest effective dose for the shortest time necessary. Topical NSAIDs are also effective in managing knee pain and have fewer systemic side effects.
