What is Knee Pain?
Knee pain explained by Denver, Golden, Aurora, Boulder, Broomfield, Jefferson, and Littleton Colorado’s top pain doctors
Knee pain is one of the most frequently reported medical complaints, especially after an injury. The knee joint is among the most complex and largest of all joints in the body. It is comprised of bones, tendons, ligaments, and muscles, in addition to thick protective layers of cartilage. The tibia, femur, patella, and fibula are the four main bones that are located in the knee. Ligaments such as the anterior cruciate ligament (ACL) connect each bone to the other, but hinder them from rubbing together. The ACL, for example, restricts the backward movement of the femur and prevents it from coming into contact with the tibia, while the posterior cruciate ligament (PCL), restricts the forward movement of the femur. Furthermore, the lateral and medial collateral ligaments restrict the side-to-side movement of the femur.
Quadricep muscles also make up the frontal portion of the knee, while hamstrings make up the back portion of this joint. Both of these structures provide added stability and support. Protective cartilage that is C-shaped, called the lateral and medial menisci, are positioned between the tibia and femur. This cartilage functions like shock absorbers that also provide a smooth surface for easy mobility. Bursae, sacs that contain synovial fluid, encase the entire knee joint to further support fluid movements. Consequently, if knee pain develops, any one of these structures or even more than one may be the cause of the pain.
The structures that make up the knee are highly susceptible to gradual wear and tear over time, damage due to injuries, and damage due to overexerting the joint. Certain environmental conditions have also been implicated in the onset of knee pain that eventually becomes chronic. For example, blunt trauma to the knee region and even an infection increases the likelihood of experiencing persistent pain and future injuries. In addition, identifying the pain source is often difficult if an individual cannot recall a specific event that may have initiated it. Furthermore, some patients report that their pain is generalized and mild while other patients report feeling localized pain that is sharp.
The Impact And Epidemiology Of Knee Pain
A recently published study reported that the incidence of knee osteoarthritis and associated knee pain has more than doubled for female patients during the last 20 years and that the numbers have tripled for male patients. These patterns were observed mainly in Mexican American women and men, African American women, and Caucasian men who are Non-Hispanic. These results were not related to weight (e.g., obesity) or age. In actuality, acute or persistent knee pain causes stability and mobility problems and a hindered ability to engage in daily activities in more than 20% of the adults who experience knee pain.
For individuals who are 50 years of age or older, osteoarthritis is usually the main reason that knee pain develops. However, younger individuals who are highly active and engage in sports or recreation regularly have a higher occurrence of knee pain. Athletes, in particular, tend to injure their knees quite frequently. Conditions such as iliotibial syndrome or a torn meniscus are also common among runners, cyclists, and people who frequently do aerobics or play sports. Furthermore, a dislocated kneecap is a common sports-related injury among adolescents; this is especially the case for girls who are 12 to 18 years old.
In addition, some diseases may cause health problems in certain age groups that affect the knee. One disease called Osgood-Schlatter disease generally causes knee pain in children, particularly boys whose ages range from 10 to 15. This condition is also called osteochondrosis or Schlatter’s disease.
A knee replacement is a surgical procedure that has rapidly increased for patients who are 60 years old or older. Most patients who undergo this procedure have experienced persistent pain in the knee and mobility problems for extended periods. However, younger patients are also starting to undergo knee replacements at a rapid rate, although older patients still receive this type of surgery more often. Overall, more than four million people in the U.S. are estimated to have received a knee replacement and the majority of them are between the ages of 50 to 70.
Causes Of Knee Pain
The most common causes of knee pain are injuries. These include strained or sprained tendons and ligaments, falling and landing on the knees, blunt trauma, improper bending of the knees, or abnormal twisting of the knees. For instance, a torn meniscus usually occurs when the knee is rotated or twisted in an abnormal and forceful manner. Strenuous work-related tasks that require repetitive movements can cause knee injuries as well.
Painful knee injuries that are more serious include a fractured or broken knee cap, tibia, fibula, or femur, which are often the result of blunt trauma, twisting improperly, or falling. Injuries such as these can cause blood vessel or nerve damage that leads to numbness. A dislocated kneecap is another painful injury that causes serious complications. More specifically, pieces of bone or tissue can tear apart from the knee, get stuck in different parts of the joint, and significantly hinder an individual’s mobility. Therefore, a dislocated knee necessitates immediate medical care.
Overexerting the knee joint or overusing it, by repeating certain movements or putting too much pressure on it, can cause the knee joint to become damaged. The following activities are commonly associated with injuries to the knee and persistent pain: climbing stairs, cycling, jumping, and jogging. Furthermore, repetitive movements such as these often result in tendinosis, tendinitis, patellofemoral pain syndrome, iliotibial band syndrome, bursitis, and plica syndrome.
Tendinosis develops when small tears occur in knee tendons, while tendinitis refers to inflamed tendons. Patellofemoral pain syndrome occurs due to knee overexertion or placing too much weight on it. The pain that is associated with this syndrome typically develops in the kneecap and the frontal regions. Bursitis is a painful condition that develops when the synovial fluid-filled sacs that encase the knee joint become inflamed. Plica syndrome develops when ligaments thicken or fold in an abnormal way, which causes pain in the back portion of the knee.
Iliotibial band syndrome is a condition in which the fibrous tissue bundle known as the iliotibial band, which under normal circumstances provides the knee joint with added stability and hinders dislocation, becomes inflamed. Overexerting the knee may cause the iliotibial band to tighten, overdevelop, or come in contact with the outer regions of the knee and this leads to complications. When this syndrome develops, an individual will notice pain when the knee is moved. Runners, cyclists, and individuals involved in regular aerobic activities tend to suffer from this syndrome.
Gout, infections, autoimmune diseases, osteoarthritis, and additional conditions can cause knee pain. Osteoarthritis is a degenerative condition that mainly affects the joints and is characterized by the extensive degeneration of cartilage in the joints. As individuals age, cartilage becomes susceptible to gradual wear and tear, although injuries may also cause cartilage to become damaged. Serious cartilage damage causes it to begin to deteriorate; allowing bones to come in contact with each other because they are no longer separated or protected by the cartilage.
Lupus and rheumatoid arthritis are autoimmune diseases that result in an abnormal immune system response that causes damage to the body’s joints. Rheumatoid arthritis is described as inflamed cartilage or muscle tissue in the joints. As the condition progresses, bones, ligaments, tendons, and cartilage in the knee, for example, can further deteriorate. Lupus presents similar symptoms as rheumatoid arthritis such as swelling in the joints (e.g., the knees), intense pain, tissue damage, and inflammation.
Inflammation of the knee can also lead to the build-up of excess fluid or a condition known as knee effusion. The accumulation of fluid is often experienced in conjunction with either moderate or intense pain. Moreover, certain types of cysts that may form in the back portion of the knee such as Baker’s cyst or popliteal cause are often associated with swelling and pain. In addition, nerves that become pinched in the hip or other health problems that may occur in different regions of the body can cause knee pain.
Pseudogout and gout are painful conditions of the joints, including the knees, characterized by the accumulation of calcium pyrophosphate crystals or uric acid crystals, respectively. Another condition that can affect the knee is called septic arthritis, which is result of a bacterial infection. Similar to other forms of arthritis, septic arthritis causes inflammation and pain. Several infections including influenza, Lyme disease, and hepatitis have also been reported to cause knee pain.
Osgood-Schlatter disease, also referred to as osteochondrosis or Schlatter’s disease, is described as the inflammation of the tibia on the top region where the tendons are attached to the bones. This disease generally causes knee pain in children, particularly boys whose ages range from 10 to 15. The knee joint is also susceptible to decreased mobility as a result of portions of bone or cartilage that die due to a loss of blood supply. This painful condition is called osteochondritis dissecans.
Certain injuries lead to the development of immediate symptoms in addition to pain such as bruising or swelling, while other injuries may not cause pain right away. In addition, the pain severity individuals experience also widely varies.
Symptoms Of Knee Pain
Knee pain is not very specific and sometimes the symptoms occur in a large area of the knee. While patients may feel pain in one area that might feel like a sudden stab, others feel it all over and it is harder to target. Minutes after a knee injury has occurred, bruising, swelling, or pain can be felt and this usually progresses after a few hours or sometimes days.
Some common symptoms that are associated with knee pain include:
- Stiffness and swelling
- Instability or weakness
- Numbness, tingling, or a cold feeling
- The locking of knee during movement
- Discoloration (e.g., pale or blue color)
- Problems straightening the knee
- Snapping, grinding, or popping noises with movement
When an injury occurs if a ligament may be torn, the person would feel or maybe even hear a snapping sound, which is a symptom of a serious knee sprain. Movement becomes limited as well as severe pain and some swelling in the area. If a ligament was torn, disfigurement or a protrusion would be seen in the affected area. Knee sprains and knee strains have similar symptoms because the muscles or tendons are affected.
An injury that requires immediate medical attention would be a knee fracture or dislocation. The symptoms would be an usual look in the area, the inability to stand or walk, trouble bending or straightening the knee or leg, swelling, a red spot, and unbearable pain. The knee joint would also become loose and unsteady.
When too much pressure is put on the knees during movement it causes inflammation and intense pain, especially for people who suffer from bursitis or tendonitis. The area is usually warm, becomes red, and swells due to fluid buildup in the area.
Pain that occurs when using the stairs, jumping, while sitting, or squatting or if the knee pops, buckles, or grinds during movement is characterized by syndromes such as patellofemoral pain syndrome and iliotibial band syndrome.
Someone who suffers from osteoarthritis will experience stiffness in the mornings due to inactivity, but pain in the knees, the spine, and the toes increases at the end of the day because of overuse. Even when the person tries to rest, the pain intensifies as the condition worsens. When fluid builds up around the joint, the knees also become enlarged.
If any of the following symptoms are experienced along with knee pain (although in most cases these symptoms are not severe), a physician should be contacted:
- Weight loss that is unintentional of approximately ten or more pounds
- A fever that is not associated with flu-like symptoms
- Knee pain that has persisted longer than three days and has begun to hinder daily activities
- Intense knee pain that is occurring along with additional, unexplained symptoms
Risk Factors For Knee Pain
Anyone who is severely obese is at a higher risk for knee pain, which leads to joint inflammation and injuries. Any activity like using the stairs or walking causes weight-related stress on the knees when a person is obese. Along with age, someone who is obese risks developing knee osteoarthritis, but more emphasis is based on obesity because the cartilage in the knee degenerates more rapidly. Statistics have shown that people who are 50 to 85, are obese, and are suffering from knee osteoarthritis lose an average of three and half of their quality years of life. Total knee replacement is another procedure that people who are obese tend to undergo as a result of prolonged complications and knee pain. Sometimes the procedures can become complicated and dangerous but this does not occur very often.
People with physical abnormalities are also more susceptible to knee problems and pain such as if one leg is shorter than the other, being flat-footed, or having knocked knees. Knee injuries also affect individuals who lack strength and flexibility in their muscles. All of these problems occur when excess stress is placed on the knee because muscles that are weak or too tight do not provide sufficient knee support. When going for long daily walks, it is important not to wear flip-flops or flat-soled sandals because they do not provide enough arch support and this can cause knee pain.
Furthermore, a lot of sporting activities such as alpine skiing, running, jogging, basketball pivots, and long jumps place a lot of pressure on the knees and the risk of injury to the knee is very high because of the high potential for falling. Some sports generally cause persistent knee pain and complications because of the constant pressure on the knees. If the knee has already been injured, it also becomes more susceptible to injuries in the future. Anyone who smokes is at risk of slowing down the healing process because the blood flow to the tissue is interrupted.
Diagnosing Knee Pain
Knee pain may develop after an injury, due to inflammation of the structures that comprise the knee joint, or various other conditions. Therefore, accurately diagnosing the pain source is critical in order to ensure that the appropriate form of treatment will be recommended. A thorough examination is imperative as dangerous health problems such as internal bleeding or blood clots could also be the cause of the knee pain.
The following questions will be asked at the consultation appointment:
- Where is the pain being felt?
- Is the pain acute or persistent?
- Is the pain minor, moderate, or intense?
- Is an increase in pain felt or worsened during movement?
- Does touching the knee make the pain worse?
- Is the knee pain due to an injury?
- Did the knee make a popping sound at the time of the injury?
- Can popping or grinding of the knee be heard during movement?
It is necessary to answer these questions because the region where the pain is being felt can help a physician determine which structure of the knee may have become injured. For example, when pain is felt primarily on one side of the knee, the iliotibial band may have become injured. Pain that occurs primarily in the frontal region of the knee may be due to patellofemoral syndrome. In addition, if the skin surrounding the knee region feels warm when it is touched, an infection may be developing in the joint. Therefore describing the way an injury happened can help a physician quickly pinpoint the cause of knee pain.
Additionally, a checklist may be used to assess whether particular symptoms may be present. These include:
- Clicking, instability, or locking which may be an indication that cartilage in the meniscus has become damaged
- Pain beneath the kneecap, specific to the tendon, which may be an indication that tendinitis is causing the pain
- Swelling in the knee which may be an indication that several structures have become affected
- The abrupt occurrence of symptoms which may be an indication that blunt trauma led to the knee injury
- Throbbing knee pain which may be an indication that overexertion or the gradual wear and tear of cartilage has occurred
- Pain during kneeling movements which is an indication of arthritis
- Stiffness specifically in the morning which can be an indication that the patient is developing osteoarthritis
- A bony mass on the front side of the knee which may be an indication that Osgood-Schlatter disease has developed (this is especially the case in adolescents)
- Numbness or tingling which is a sign that blood vessel or nerve damage has occurred in the knee due to a serious injury
Visualizing the internal components of the knee can also help a physician make an accurate diagnose, and therefore, imaging screenings may be performed. An X-ray is the most commonly used imaging technique. Additional screening techniques that may be utilized as diagnostic tools include ultrasound, magnetic resonance imaging (MRI), or a computerized tomography (CT) scan. Degenerative joint disease or fractures can be detected with the use of an X-ray. Loose structures such as bone or tissue can be detected through a CT scan. An MRI or ultrasound allows the visualization of soft tissue such as tendons, ligaments, cartilage, and muscles.
If it is suspected that a condition such as pseudogout or gout may be the pain source, then blood tests are usually performed. In addition, arthrocentesis, which is a procedure that involves analyzing fluid that has been removed directly from the knee, may be conducted as well.
Treatments For Knee Pain
Knee pain treatments include:
- Home remedies, such as using hot and cold packs, a knee brace, and resting, or taking prescription pain medication or over-the-counter pain relievers
- Engaging in physical therapy
- Undergoing surgery in extreme cases
The treatment approach that is recommended, however, usually depends on the location, severity, and type of injury or condition that caused the knee pain. Additional factors that play a role in treatment decisions are age, health status, and level of activity (e.g., hobbies, sports, or work schedule).
In certain circumstances, when knee pain does not decrease after different types of pain relievers or injections have been administered or apparent nerve damage has occurred, a physician may recommend spinal cord stimulation. This procedure involves the implantation of electrodes into the tissue that surrounds the nerves that are responsible for the knee pain. The pain doctor then administers a mild electrical current that disrupts the pain signals and provides the patient with relief.
This procedure does, however, require two stages. The first stage involves a trial period in which temporary electrodes are implanted and stimulation is received for approximately one week. This trial period demonstrates whether or not the nerve stimulation will effectively reduce the patient’s knee pain. If the trial phase is ineffective, the temporary electrodes can easily be removed and then alternative treatment methods can be discussed. If the trial period does provide some pain relief, then the second stage will involve surgically implanting permanent electrodes in the region of the body where the affected nerves are located.
If spinal cord stimulation is not a valid option for an individual who has experienced a serious knee injury that has significantly altered their quality of life, a total knee replacement may be considered. Individuals who have advanced stages of osteoarthritis in the knee may also elect to undergo joint replacement surgery. Home remedies are generally effective at treating the early stages of osteoarthritis, but this condition usually progresses over time; eventually making it necessary to consider receiving a knee joint replacement. Reports have indicated that effective total knee replacement surgeries generally increase an individual’s quality of life by five or six years in comparison to individuals who have serious knee problems but decide not to undergo this type of operation.
Treatments that are suggested primarily focus on alleviating or reducing chronic pain, while improving mobility. If an individual reports that the pain is minor or moderate and is not the result of a severe injury (e.g., a dislocation, fracture, or infection), then home remedies may be initially recommended by a physician to help reduce the pain as well as symptoms such as stiffness and swelling.
Frequently recommended home treatments include:
- Immediately applying ice or a cold pack to the knee if an injury has occurred in order to hinder or decrease swelling. The ice or cold pack should be applied for at least ten and up to 20 minutes about three times daily.
- Protecting and resting the knee joint or the sore area from another injury by using a brace. This also means refraining from activities that could cause the soreness and pain to worsen.
- Refraining from taking hot showers, using hot packs, and sitting in a hot tub for at least two days following the injury.
- Applying heat to the knee two to three days after the swelling has stopped as well as beginning to gently exercise the joint. Applying moist heat helps restore mobility and flexibility.
- Tightly wrapping or compressing the knee with a bandage made out of elastic such as an Ace wrap. However, wrapping the knee too tight can actually increase swelling. Numbness, tingling, swelling of the skin around the bandage, and an increase in pain are indications that the bandage is too tight. It is important to remember that this type of bandage is meant to decrease swelling; it does not prevent re-injury or stabilize the knee.
- Elevating the injured knee while sitting down, lying down, or resting
- Gently massaging the knee in order to enhance blood flow. However, if it causes pain, discontinue massaging the knee.
- Performing exercises, such as the knee to chest stretch or the hamstring stretch, in a gentle manner to ensure that the knee remains flexible. High-impact sports such as running, tennis, snowboarding, and skiing should be avoided until the pain and swelling has completely stopped.
- Avoiding smoking as it reduces blood flow, which delays the repair of knee tissue and slows the healing and recovery process.
Different home remedies may also be recommended depending on how the knee became injured. For instance, a mild muscle strain or ligament sprain should be treated by immobilizing the knee, resting and elevating it, applying ice packs, and wrapping it with a compression bandage. Strains or sprains that result in moderate to intense pain need to be examined by a physician who will decide if a cast, splint, and medication may be needed or if the injury may require physical therapy or surgery. If a severe knee injury is not treated properly, chronic pain, deformities, and mobility problems may develop.
A torn meniscus should be treated with therapy that focuses on helping the patient regain mobility in the knee. Common home remedies for this injury include pain relievers, hot and cold packs, physical therapy, and compression. Patients who undergo surgery for a torn meniscus should continue with at-home treatments after surgery.
Bursitis that affects the knee responds well to cold packs, resting, and avoiding strenuous activities that can increase the pain. If the knee becomes red and feels warm when it is touched, this could mean that an infection has developed and medical care would be necessary at this point.
Similarly, the symptoms of iliotibial band syndrome often improve with rest or after taking medication that reduces pain and inflammation. A physical therapist or physician may also recommend certain stretching exercises that can be performed. The administration of steroid injections also effectively treat this condition.
The symptoms that are associated with patellofemoral pain syndrome, a condition that typically occurs in teenagers, manual laborers, and athletes, often improve when movements that bend the knee are avoided such as squatting and kneeling as well as exercises that necessitate these types of movements. In addition, non-steroidal anti-inflammatory drugs (NSAIDs), ice packs, and resting effectively relieve pain. Moreover, physical therapy is quite helpful at restoring strength, stability, and flexibility in the knee and leg muscles. However, a knee brace may be necessary for temporary stabilization of the knee. If all of these methods are ineffective at improving the symptoms, then surgery may be necessary.
Pharmaceutical treatments focus on decreasing knee pain and allowing individuals to engage in their daily routines. Physicians typically recommend non-steroidal anti-inflammatory drugs (NSAIDs) as one of the first treatment approaches for knee pain. These include over-the-counter or prescription strength Motrin or Advil (e.g., ibuprofen), or additional pain relievers such as Tylenol (e.g., acetaminophen), Naprosyn or Aleve (e.g., Naproxen), and Bufferin or Bayer (e.g., aspirin). These medications effectively reduce inflammation in the knee in most cases, and in doing so, relieve pain. However, reports indicate that NSAIDs should not be taken for at least 24 hours after the knee has become injured because this type of drug reduces the body’s ability to form blood clots. This can cause complications if a bruise develops beneath the skin. Hindering the formation of blood clots can lead to the harmful accumulation of blood at the injury site.
If over-the-counter medications such as NSAIDS do not effectively reduce the pain, a physician may recommend an opioid medications to help manage the pain, such as oxycodone, codeine, and morphine. This class of drugs is stronger than NSAIDs and is particularly effective at relieving chronic leg pain. The ability of opioids to reduce pain is attributed to the manner in which they bind to opioid receptors in the brain. Research has demonstrated that opioids provide short-term relief of intense pain that has a sudden onset. The side effects that may occur after taking opioids on a regular basis include sweating, dizziness, sexual impotence, and constipation. However, the prolonged consumption of opioids may lead to drug abuse, dependence, or even an overdose.
Knee joint corticosteroid injections are a treatment approach for individuals who are experiencing debilitating knee pain. This type of injection involves administering medication to the area that surrounds the irritated knee joint or directly into the joint. Local anesthesia is applied to the skin and then an imaging device such as an X-ray or fluoroscope is used to guide the thin needle that is inserted into the targeted region of the joint. Contrast dye is also injected to help ensure that the needle will be properly placed before the corticosteroids are injected and to make sure that the medication will be appropriately distributed to the targeted region. Anesthesia is administered to the knee in order to block the transfer of pain signals to the brain and spinal cord. In addition to anesthesia, corticosteroids are then injected into the areas where the largest amount of inflammation is observed.
Clinical trials have shown that injecting corticosteroids into the tissue surrounding the joint or directly into a joint provides patients with more pain relief than placebo injections. Furthermore, the effects of the injections were reported to last for at least one month.
A similar treatment that involves injecting steroids into the knee joint is called joint injections. Individuals who have arthritis usually receive these types of injections. Patients have generally reported experiencing immediate pain relief after undergoing either of these procedures and, if the desired amount of pain relief is not achieved initially, the injections can be safely repeated.
Patients who have osteoarthritis in the knee may need to undergo several medial branch blocks. Surgery is not necessary for a medial branch block and this procedure is minimally invasive. Anesthesia and a steroid are administered to the targeted nerve bundle that is inflamed and this procedure blocks pain signal transmission. A substance that completely destroys nerve tissue may also be injected. This method has been reported to lead to long-term relief of knee pain related to osteoarthritis.
Persistent knee pain is a frequent complaint among adults. There are numerous causes of knee pain. Factors such as injuries, osteoarthritis, muscle sprains or strains, nerve damage, bone fractures, and different diseases contribute to the occurrence of knee pain. Factors such as aging, obesity, physical abnormalities, smoking, previous injuries, and shoes with limited arch support are also associated with knee pain. Symptoms that may also develop include muscle weakness, numbness, radiating pain, cramping, tingling, muscle spasms, stiffness, and sensitivity to pressure or touch. Accurately diagnosing the pain source is critical in order to ensure that the appropriate form of treatment is recommended. A thorough examination is imperative as dangerous health problems such as internal bleeding or blood clots could be the cause of the knee pain.
Various, effective treatment approaches are available for knee pain once the pain source has been accurately identified. A physician will also evaluate whether a particular type of infection or condition may be responsible for the pain. At-home treatments are typically recommended for mild pain, including cold packs, elevation, or NSAIDs such as Tylenol (e.g., acetaminophen), Motrin or Advil (e.g., ibuprofen), and Bufferin or Bayer (e.g., aspirin). These treatment methods are typically utilized before more invasive approaches are suggested.
Severe and persistent pain, dislocations, or fractures require immediate medical care and treatment methods such as steroid injections, corticosteroid injections, spinal cord stimulation, a medial branch block, or surgery. Overall, if a serious injury has occurred or a known condition is the reason for intense knee pain, a physician will be able to recommend the optimal method of treatment after a proper diagnosis has been made.
- Haviv B, Bronak S, Thein R. The complexity of pain around the knee in patients with osteoarthritis. Isr Med Assoc J. 2013;15(4):178-181.
- Hirsch G, Kitas G, Klocke R. Intra-articular corticosteroid injection in osteoarthritis of the knee and hip: Factors predicting pain relief-a systematic review. Semin Arthritis Rheum. 2013;42(5):451-473.
- Karlsson J, Söderström A, Augustini B, Berggren AC. Is buprenorphine transdermal patch equally safe and effective in younger and elderly patients with osteoarthritis-related pain? Results of an age-group controlled study. Curr Med Res Opin. 2013; in press.
- Kwofie MK, Shastri UD, Gadsden JC, Sinha SK, Abrams JH, Xu D, Salviz EA. The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med. 2013;38(4):321-325.
- Losina E, Walensky RP, Kessler CL, Emrani PS, Reichmann WM, Wright EA, Holt HL, Solomon DH, Yelin E, Paltiel AD, Katz JN. Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume. Arch Intern Med. 2009;169(12):1113-1121
- Losina E, Walensky RP, Reichmann WM, Holt HL, Gerlovin H, Solomon DH, Jordan JM, Hunter DJ, Suter LG, Weinstein AM, Paltiel AD, Katz JN. Impact of obesity and knee osteoarthritis on morbidity and mortality in older Americans. Ann Intern Med. 2011;154(4):217-226.
- Maricar N. Callaghan MJ, Felson DT, O’Neill TW. Predictors of response to intra-articular steroid injections in knee osteoarthritis-a systematic review. Rheumatology. 2013;52(6):1022-1032.
- Marks R. Obesity Profiles with Knee Osteoarthritis: Correlation with Pain, Disability, Disease Progression. Obesity. 2007;15:1867-1876.
- Nguyen US, Zhang Y, Zhu Y, Niu J, Zhang B, Felson DT. Increasing prevalence of knee pain and symptomatic knee osteoarthritis: Survey and cohort data. Am Intern Med. 2011;155(11):725-732.
- Porcheret M, Jordan K, Croft P, Treatment of knee pain in older adults in primary care: Development of an evidence-based model of care. Rheumatology.2007;46:638-648.
- Stein BE, Srikumaran U, Tan EW, Freehill MT, Wilckens JH. Lower-extremity peripheral nerve blocks in the perioperative pain management of orthopaedic patients: AAOS exhibit selection. J Bone Joint Surg Am. 2012;94(22):e167.
- Weinstein AM, Rome BN, Reichmann WM, Collins JE, Burbine SA, Thornhill TS, Wright J, Katz JN, Losina E.Estimating the burden of total knee replacement in the United States. J Bone Joint Surg Am. 2013;95(5):385-392.