Knee pain is

pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...

in or around the

knee In humans and other primates, the knee joins the thigh with the leg and consists of two joints: one between the femur and tibia (tibiofemoral joint), and one between the femur and patella (patellofemoral joint). It is the largest joint in the hu ...

. The

joint consists of an articulation between four bones: the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

and

patella The patella (: patellae or patellas), also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in m ...

. There are four compartments to the knee. These are the medial and lateral tibiofemoral compartments, the patellofemoral compartment and the superior tibiofibular joint. The components of each of these compartments can experience repetitive strain, injury or disease. Running long distance can cause pain to the knee joint, as it is a high-impact exercise. The location and severity of knee pain may vary, depending on the cause of the problem. Signs and symptoms that sometimes accompany knee pain include: * Swelling and stiffness * Redness and warmth to the touch * Weakness or instability * Popping or crunching noises * Inability to fully straighten the knee

Causes

Injuries

Some common injuries based on the location include: *

Sprain A sprain is a soft tissue injury of the ligaments within a joint, often caused by a sudden movement abruptly forcing the joint to exceed its functional range of motion. Ligaments are tough, inelastic fibers made of collagen that connect two or ...

(Ligament sprain) **

Medial collateral ligament The medial collateral ligament (MCL), also called the superficial medial collateral ligament (sMCL) or tibial collateral ligament (TCL), is one of the major ligaments of the knee. It is on the medial (inner) side of the knee joint and occurs in ...

** Lateral collateral ligament **

Anterior cruciate ligament The anterior cruciate ligament (ACL) is one of a pair of cruciate ligaments (the other being the posterior cruciate ligament) in the human knee. The two ligaments are called "cruciform" ligaments, as they are arranged in a crossed formation. In ...

Posterior cruciate ligament The posterior cruciate ligament (PCL) is a ligament in each knee of humans and various other animals. It works as a counterpart to the anterior cruciate ligament (ACL). It connects the posterior intercondylar area of the tibia to the Medial condyl ...

Tear of meniscus A tear of a meniscus is a rupturing of one or more of the fibrocartilage strips in the knee called meniscus (anatomy), menisci. When doctors and patients refer to "torn cartilage" in the knee, they actually may be referring to an injury to a meni ...

** Medial meniscus **

Lateral meniscus The lateral meniscus (external semilunar fibrocartilage) is a fibrocartilaginous band that spans the lateral side of the interior of the knee joint. It is one of two menisci of the knee, the other being the medial meniscus. It is nearly circular ...

* Strain (Muscle strain) ** Quadriceps muscles ** Hamstring muscles **

Popliteal muscle The popliteus muscle in the leg is used for unlocking the knees when walking, by laterally rotating the femur on the tibia during the closed chain portion of the gait cycle (one with the foot in contact with the ground). In open chain movements ...

Patellar tendon The patellar tendon is the distal portion of the common tendon of the quadriceps femoris, which is continued from the patella to the tibial tuberosity. It is also sometimes called the patellar ligament as it forms a bone to bone connection whe ...

**Hamstring tendon **Popliteal tendon *

Hemarthrosis Hemarthrosis is a bleeding into joint spaces. It is a common feature of hemophilia. Causes It usually follows injury but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin (or other anticoagu ...

– Hemarthrosis tends to develop over a relatively short period after injury, from several minutes to a few hours.

Fractures

* Femoral fracture * Tibial fracture * Patella fracture

Diseases

Some of the diseases of cause of knee pain include the following: * Knee osteoarthritis * Chondromalacia patella * Baker's cyst * Meniscal cyst *

Discoid meniscus Discoid meniscus is a rare human anatomic variant that usually affects the lateral meniscus of the knee. Usually a person with this anomaly has no complaints; however, it may present as pain, swelling, or a snapping sound heard from the affected k ...

* Osgood-Schlatter disease * Larsen-Johansson disease *Knee

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

Osteochondritis dissecans Osteochondritis dissecans (OCD or OD) is a joint disorder primarily of the subchondral bone in which cracks form in the articular cartilage and the underlying subchondral bone. OCD usually causes pain during and after sports. In later stages o ...

disease * Synovial chondromatosis disease *

Tumors A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

Ankylosing spondylitis Ankylosing spondylitis (AS) is a type of arthritis from the disease spectrum of axial spondyloarthritis. It is characterized by long-term inflammation of the joints of the spine, typically where the spine joins the pelvis. With AS, eye and bow ...

Reactive arthritis Reactive arthritis, previously known as Reiter's syndrome, is a form of inflammatory arthritis that develops in response to an infection in another part of the body (cross-reactivity). Coming into contact with bacteria and developing an infect ...

* Tuberculosis arthritis *

Septic arthritis Acute septic arthritis, infectious arthritis, suppurative arthritis, pyogenic arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typica ...

(''Pyogenic arthritis'') *

Osteomyelitis Osteomyelitis (OM) is the infectious inflammation of bone marrow. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The feet, spine, and hips are the most commonly involved bones in adults. The cause is ...

* Hemophilic arthritis *

Gout Gout ( ) is a form of inflammatory arthritis characterized by recurrent attacks of pain in a red, tender, hot, and Joint effusion, swollen joint, caused by the deposition of needle-like crystals of uric acid known as monosodium urate crysta ...

(Gouty arthritis) * Neuroma

Inflammations

Bursitis Bursitis is the inflammation of one or more bursae (synovial sacs) of synovial fluid in the body. They are lined with a synovial membrane that secretes a lubricating synovial fluid. There are more than 150 bursae in the human body. The bursae (bu ...

of the knee ** Prepatellar bursitis - Housemaid's knee (most common) ** Infrapatellar bursitis - Clergyman's knee (''Superficial infrapatellar bursitis'' and ''Deep infrapatellar bursitis'') **Semimembranosus bursitis *

Tendinitis Tendinopathy is a type of tendon disorder that results in pain, swelling, and impaired function. The pain is typically worse with movement. It most commonly occurs around the shoulder ( rotator cuff tendinitis, biceps tendinitis), elbow ( tenn ...

Patellar tendinitis Patellar tendinitis, also known as jumper's knee, is an overuse injury of the tendon that straightens the knee. Symptoms include pain in the front of the knee. Typically the pain and tenderness is at the lower part of the kneecap, though the ...

(''Jumper's knee'') **

Hamstring A hamstring () is any one of the three posterior thigh muscles in human anatomy between the hip and the knee: from medial to lateral, the semimembranosus, semitendinosus and biceps femoris. Etymology The word " ham" is derived from the Old ...

tendinitis **Popliteal tendinitis *

Synovitis Synovitis is the medical term for inflammation of the synovial membrane. This membrane lines joints that possess cavities, known as synovial joints. The condition is usually painful, particularly when the joint is moved. The joint usually swells ...

of the knee

Deformities

Common deformities of the knee include: *

Bipartite patella Bipartite patella is a condition where the patella, or kneecap, is composed of two separate bone, bones. Instead of ossification, fusing together as normally Patella#development, occurs in early childhood, the bones of the patella remain separated ...

(two-part kneecap) *

Genu varum Genu varum (also called bow-leggedness, bandiness, bandy-leg, and tibia vara) is a varus deformity marked by (outward) bowing at the knee, which means that the lower leg is angled inward ( medially) in relation to the thigh's axis, giving th ...

(bow legs) *

Genu valgum Genu valgum, commonly called "knock-knee", is a condition in which the knees angle in and touch each other when the human leg, legs are straightened. Individuals with severe valgus deformity, valgus deformities are typically unable to touch thei ...

(knock-knees) * Genu recurvatum ( Knee hyperextension) * Knee flexion deformity

Syndromes

* Patellofemoral pain syndrome * Plica syndrome *

Iliotibial band syndrome Iliotibial band syndrome (ITBS) is the second most common knee injury, and is caused by inflammation located on the lateral aspect of the knee due to friction between the iliotibial band and the lateral epicondyle of the femur. Pain is felt most ...

* Hoffa's syndrome * Joint hypermobility syndrome

Dislocations

* Patella dislocation * Knee joint dislocation (''Tibiofemoral joint dislocation'')

Cold temperature

Knee pain is more common among people working in the cold than in those in normal temperature. Cold-induce
knee pain
may also be due to

tenosynovitis Tenosynovitis is the inflammation of the fluid-filled sheath (called the synovium) that surrounds a tendon, typically leading to joint pain, swelling, and stiffness. Tenosynovitis can be either infectious or noninfectious. Common clinical mani ...

of the

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

s around the knee, in which cold exposure has a specific role, either as a causative or a contributing factor. Frank

arthritis Arthritis is a general medical term used to describe a disorder that affects joints. Symptoms generally include joint pain and stiffness. Other symptoms may include redness, warmth, Joint effusion, swelling, and decreased range of motion of ...

has been reported in children due to

frostbite Frostbite is a skin injury that occurs when someone is exposed to extremely low temperatures, causing the freezing of the skin or other tissues, commonly affecting the fingers, toes, nose, ears, cheeks and chin areas. Most often, frostbite occ ...

from extreme cold causing direct

chondrocyte Chondrocytes (, ) are the only cells found in healthy cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans. Although the word '' chondroblast'' is commonly used to describe an immatu ...

injury. There is also a

hereditary disease A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality. Although polygenic disorders are ...

, familial cold autoinflammatory syndrome (FCAS), which often features knee pain, in addition to hives, fever and pain in other joints, following general exposure to cold.

Knee pain due to less physical movement

A lower level of physical activity and a work environment where one is required to sit in a chair during the work day is one reason for developing knee joint pain, as the lower degree of physical movement tends to weaken the knee muscles. Blood vessels also can be affected, leading to development of painful conditions. Working on building strength through a full range of motion is crucial for rebuilding strength and getting rid of knee pain. As age progresses the movement of the knee joint involves higher friction with adjacent tissue and cartilages.

Other causes

Ligamentous laxity Ligamentous laxity or ligament laxity can appear in a variety of ways and levels of severity. In most people, ligaments (which are the tissues that connect bones to each other) are naturally tight in such a way that the joints are restricted to ...

* Fat pad impingement * Knee effusion *

Deep vein thrombosis Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enl ...

Peripheral vascular disease Peripheral artery disease (PAD) is a vascular disorder that causes abnormal narrowing of arteries other than those that supply the heart or brain. PAD can happen in any blood vessel, but it is more common in the legs than the arms. When narro ...

Exostosis An exostosis, also known as a osteochondroma, is a benign chondrogenic lesions derived from aberrant cartilage from the perichondral ring. Exostoses can cause chronic pain ranging from mild to moderate, but rarely severe, depending on the shape, s ...

Referred knee pain

Referred pain Referred pain, also called reflective pain, is pain perceived at a location other than the site of the painful stimulus. An example is the case of angina pectoris brought on by a myocardial infarction (heart attack), where pain is often felt in t ...

is that pain perceived at a site different from its point of origin but innervated by the same spinal segment. Sometimes knee pain may be related to another area from body. For example, knee pain can come from ankle, foot, hip joints or

lumbar spine The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...

Diagnosis

Knee MRIs should be avoided for knee pain without symptoms or

effusion In physics and chemistry, effusion is the process in which a gas escapes from a container through a hole of diameter considerably smaller than the mean free path of the molecules. Such a hole is often described as a ''pinhole'' and the escape ...

, unless there are non-successful results from a functional rehabilitation program. * * * * * In some diagnosis, such as in knee osteoarthritis, magnetic resonance imaging does not prove to be clear for its determination.

Management

Although surgery has a role in repairing traumatic injuries and broken bones, arthroscopic surgeries do not provide significant or lasting improvements to either pain or function to people with knee pain, and therefore should almost never be performed. Knee pain is pain caused by wear and tear, such as

osteoarthritis Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affect ...

or a meniscal tear. Effective treatments for knee pain include

physical therapy Physical therapy (PT), also known as physiotherapy, is a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

exercises, pain-reducing drugs such as

ibuprofen Ibuprofen is a nonsteroidal anti-inflammatory drug (NSAID) that is used to relieve pain, fever, and inflammation. This includes dysmenorrhea, painful menstrual periods, migraines, and rheumatoid arthritis. It can be taken oral administration, ...

, joint stretching,

knee replacement Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability, most commonly offered when joint pain is not diminished by conservative sources. ...

surgery, and weight loss in people who are overweight. Overall, a combination of interventions seems to be the best choice when treating knee pain. Interventions such as exercises that target both the knee and the hip, foot bracing, and patellar taping are all recommended for use with patients who have knee pain. Current evidence suggests that psychological factors are elevated in individuals with patellofemoral pain. Non-physical factors such as anxiety, depression, fear of movement, and catastrophizing are thought to have a linear correlation with increased pain experience and decreased physical function. Catastrophizing is defined as imagining the worst possible outcome of an action or event. The psychosocial factors may have either a positive or negative impact on adherence to rehabilitation programs for managing knee pain. Furthermore, studies have found knee pain to be negatively associated with health-related quality of life, and an increase in knee pain to be associated with a reduction in patient-reported quality of life, as compared to those with no or stable knee pain, even in the relatively younger middle-aged population.

Epidemiology

About 25% of people over the age of 50 experience knee pain from degenerative knee diseases.

Society and culture

In the United States, more than US$3 billion is spent each year on arthroscopic knee surgeries that are known to be ineffective in people with degenerative knee pain.

References

External links

{{Medical resources , ICD10 = , ICD9 = , ICDO = , OMIM = , DiseasesDB = , MedlinePlus = 003187 , eMedicineSubj = , eMedicineTopic = , MeshID = Musculoskeletal disorders Rheumatology Orthopedic problems

Pain Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...