Figure 13.1
The knee: posterior and anterior views
Introduction
The knee is the most common joint to develop osteoarthritic changes globally, and it is reported in over 9 million people in the United States alone (Helmick et al 2008, Lawrence et al 2008). It is also the most reported joint for disability and symptoms (Corti & Rigon 2003, De Filippis et al 2004, Arden & Nevitt 2006). Osteoarthritic changes within the knee can be observed in approximately 70% of symptomatic individuals and approximately 40% of asymptomatic individuals aged 40 or over (Du et al 2005, Englund et al 2008).
Knee surgery, particularly arthroscopy, has been increasingly used over the past decade (Kim et al 2011, Bohensky et al 2012, Harris et al 2013, Thorlund et al 2014), although some would question the long-term benefits of this procedure (Katz et al 2013, Yim et al, 2013). There have always been protocols with regard to postoperative care for individuals following knee surgery, but there is growing evidence for both short- and long-term benefits from preoperative care (Ackerman & Bennell 2004, Wallis & Taylor 2011, Hoogeboom et al 2012), exercise-based or manual therapy. In the first stage of postoperative rehabilitation (2–3 weeks) following knee arthroscopy, it is recommended that articulation of the joint is performed to help aid the range of movement and fluid dynamics of the knee (UW Health 2011). Grella (2013) also suggests that early articulation of the joint is more beneficial than continuous passive motion of the knee following surgery.
Osteoarthritis: National Clinical Guideline for Care and Management in Adults (NICE 2008) recommends articulation as a core component of treatment of knee arthritis. Moss et al (2007) established that articulation of degenerative knees caused a neurological hypoalgesic effect in local and distal tissues. Sluka and colleagues (2006) discovered similar reductions in pain thresholds with the rhythmical articulation of chronically inflamed rat knee joints. It was also found that the decrease in pain threshold caused was bilateral, thus suggesting the involvement of a central neurological component. Pollard et al (2008) found that a short-term course of manual therapy to arthritic knees reduced reported pain symptoms.
Manual therapy combined with exercise can reduce the need for surgical intervention with arthroplasty and intra-articular injections (Deyle et al 2000). Fransen et al (2001) found that manual therapy of the knee caused not only a decrease in reported pain levels but also an increase in quality of life. In their trial, Crossley et al (2002) found that a course of 6 weeks of manual therapy and prescribed exercises decreased the perceived pain, disability and impairment of patients who suffered with patella–femoral pain. These findings are also reflected in studies by Taylor and Brantingham (2003), Stakes et al (2006) and Collins et al (2012).
Anatomy
The largest and most complex joint in the human body, the knee comprises bones, cartilage, ligaments and tendons. The knee joint connects the upper and lower leg bones, and is the anatomical region where four bones – the femur, tibia, fibula and patella – meet. Apart from the fibula, all these bones are functional in the knee joint (Kishner et al 2015).
The knee is a synovial (modified hinge) joint, consisting of three distinct and partially separated compartments. The main knee joints, known as the tibiofemoral joints, have a medial and a lateral compartment. These joints are formed between the medial and lateral condyles of the femur (thigh bone) and the medial and lateral condyles of the tibia (shin bone). Two wedge-shaped articular discs (the medial meniscus and lateral meniscus) provide padding and support between the femoral condyles and tibial condyles. The third knee joint, called the femoropatellar joint, is found between the kneecap (patella) and the distal femur. All of these joints are surrounded by a single articular capsule and the ligaments strap the inside and outside of these articulations (Tate 2009).
The knee is well constructed for transmitting the body weight in vertical and horizontal directions. It ensures weight-bearing support by allowing flexion and extension of the leg. It also allows a small amount of internal and external rotation when the knee is flexed, but not when it is extended. The stability and normal movements at the knee are essential in performing many daily activities, such as walking, running, kicking, sitting and standing (Mader 2004).
Bony anatomy
Femur
The femur is an important component of the appendicular skeleton and is the longest and strongest bone in the human body. The mean ratio of femur length to stature is 26.74%, with a very limited variation in both men and women and most ethnic groups (Feldesman et al 1990).
The femur is located in the thigh, extending from the hip to the knee. The proximal end of the femur has a smooth, spherical process called the femur head, which articulates with the acetabulum. The distal end of the femur has a double condyle that articulates with the proximal condyles of the tibia. The femurs support the weight of the body during many everyday activities, including walking, running, jumping and standing (OpenStax 2013).
Tibia
The tibia, also known as the shin bone, is the medial bone of the leg. It is located medial to the fibula and distal to the femur. It is the longest bone of the body after the femur and is larger and stronger than the fibula. It makes up the knee joint, articulating with the medial and lateral condyles of the femur; it forms the ankle joint, joining with the fibula and tarsus. The tibia articulates with the fibula by an interosseous membrane, forming a joint known as the syndesmosis joint (Standring 2008).
The tibia is the main bone of the lower leg that carries the weight of the body. The movement of the tibia is vital in executing numerous activities of the legs, such as running, walking and jumping.
Fibula
Also called the calf bone, the fibula is the slenderest of all the long bones. It runs parallel to the tibia and is found on the lateral side of the leg. It is connected to the tibia from above and below. It is smaller than the tibia and considerably thinner. The fibula has no articulation with the femur and patella (Mader 2004).
The fibula bears little or no weight of the body. It is largely surrounded by muscles and serves primarily for muscle attachment. It plays a major role in stabilizing the ankle and functions as a support for the tibia.
Patella
The patella, also known as the kneecap, is a large sesamoid bone. Although its shape may vary slightly from person to person, it is usually a flat triangular-shaped bone, with the apex facing downwards. The posterior region of the patella is connected with the femur; the base is attached to the tendon of the quadriceps extensor muscle, the large muscle group that covers the front and sides of the thigh. The patella has no articulation with the tibia. Functionally, it serves to protect the front of the knee joint (OpenStax 2013).
Ligaments
The knee joint has multiple ligaments that hold together the knee bones, protect the articular capsule and stabilize the joint. These ligaments are divided into two types: the extracapsular and the intracapsular ligaments. The extracapsular ligaments are found on the inner and outer sides of the knee joint. These ligaments include the fibular (lateral) collateral ligament, tibial (medial) collateral ligament, arcuate popliteal ligament, and oblique popliteal ligament. The intracapsular ligaments are located on the central part of the knee joint. They include the anterior cruciate ligament, posterior cruciate ligament and posterior meniscofemoral ligament (Kishner et al 2015).
Movement type | Range of motion(°) |
Flexion | 120–150 |
Extension | 5–10 |
Lateral (external) rotation (knee flexed 90°) | 30–40 |
Medial (internal) rotation (knee flexed 90°) | 10 |
Table 13.1
Normal range of motion of the knee
Data from Schünke et al (2006)
|
| Range of motion (°) | |
Age (years) | Movement type | Males | Females |
2–8 | Flexion | 147.8 (146.6–149.0) | 152.6 (151.2–154.0) |
Extension | 1.6 (0.9 –2.3) | 5.4 (3.9–6.9) | |
9 –19 | Flexion | 142.2 (140.4–144.0) | 142.3 (140.8–143.8) |
Extension | 1.8 (0.9 –2.7) | 2.4 (1.5–3.3) | |
20–44 | Flexion | 137.7 (136.5–138.9) | 141.9 (140.9–142.9) |
Extension | 1.0 (0.6–1.4) | 1.6 (1.1–2.1) | |
45–69 | Flexion | 132.9 (131.6–134.2) | 137.8 (136.5–139.1) |
Extension | 0.5 (0.1–0.9) | 1.2 (0.7–1.7) | |
Table 13.2
Reference values for normal knee range of motion
Data from Soucie et al (2011)
| Range of motion (°) | ||
Movement type | Visual estimation | Hand goniometry | Radiographic goniometry |
Flexion | 146 | 138 | 144 |
Extension | –3.5 | –6.3 | –4.2 |
Table 13.3
Comparison of three measurement methods of the knee for flexion and extension
Four of the knee ligaments – the lateral and medial collateral ligaments and the anterior and posterior cruciate ligaments – primarily serve to maintain the knee joint stability, restricting abnormal or excessive movements. The lateral and medial collateral ligaments prevent the femur from sliding side to side on the tibia. The anterior and posterior cruciate ligaments form an x-shape when they pass each other (hence their names) and prevent the femur from tipping backward and forward on the tibia (OpenStax 2013).
Range of motion
The knee joint allows flexion and extension, with slight internal and external rotation about the axis of the lower leg in the flexed position (see Table 13.1). Typical ranges of flexion and extension vary with age (see Table 13.2). The range of motion of the knee is typically measured using a hand goniometer but visual estimation and radiographic goniometry may also be used (see comparisons in Table 13.3).
Epidemiology
Knee pain
Knee pain is a very common condition and one that many people experience at some stage in their lives. It affects very large numbers of people indiscriminately across the world, and causes substantial social burden and persistent impairment of physical function.
Knee pain is common in all populations, including the very young and old, men and women, and athletes of numerous sports. In the UK general population aged 16+ years, the prevalence of knee pain (lasting for more than a week in the past month) was reported as 19% in 4515 respondents (Webb et al 2004). The same survey reported that the prevalence in participants over 45 years of age was slightly higher in females than in males and that, in people aged 75+ years, the prevalence in females was 36% while in males it was 27%. In pre-adolescent schoolchildren of 8–13 years of age, the prevalence of knee pain (occurring at least once a week) was 12% in 1756 participants (El-Metwally et al 2006).
Condition | Description | Reference |
Knee osteoarthritis | Represents a major cause of disability, functional limitation, morbidity, social isolation and reduced quality of life Extremely common in elderly people Prevalence rate: 14–34% (among people aged 45+ years) Symptoms include pain, impaired function, grating or grinding sensation, stiffness in the morning, and soft or hard swellings Risk factors include overweight, over 50 years of age, female sex, overwork, previous knee injury and family history of osteoarthritis | Dawson et al (2004), McRae (2010) |
Patellar chondromalacia | The most common cause of runner’s knee pain Characterized by softening or fibrillation of the patellar articular cartilage Occurs because of the repeated microtrauma or malalignment of the patella Commonest in females of 15–35 years age group Causes include a mechanical problem at the foot, tibia or hip, asynchronous muscle firing, connective tissue tightness and muscle tightness or weakness | Hartley (1995) |
Osteochondritis dissecans | A common idiopathic condition that affects the articular cartilage and subchondral bone Occurs most commonly in men in the 2nd decade of life Male-to-female ratio: 2–3:1 Can affect both younger children and adults Causes 50% of loose bodies in the knee Affects the medial femoral condyle in 85% of cases | Jacobs (1992), Flynn et al (2004), McRae (2010) |
Patellar tendonitis | An inflammation of the patellar tendon at the inferior patellar region or at the insertion of the quadriceps tendon at the base of the patella Occurs most commonly in teenage boys, particularly in athletes who actively participate in jumping sports Often associated with excessive foot pronation, patellar malalignment or patella alta Symptoms include anterior knee pain and localized swelling, thickening or nodules | Hartley (1995), Calmbach & Hutchens (2003b) |
Iliotibial band syndrome | A common cause of lateral knee pain Occurs most frequently in people who are involved in repetitive knee flexion, such as cycling and running Often caused by friction between the iliotibial band and the lateral femoral epicondyle during flexion and extension of the knee Responsible for 12% of all running-related overuse injuries Risk factors include overpronation, genu varum, length discrepancy of the limb and myofascial restriction | Hartley (1995), Lavine (2010) |
Table 13.4
Common disorders of the knee
The prevalence of knee pain increases with age in both men and women; thus, knee pain is a common complaint in the elderly. Over the past few decades, a number of studies have estimated the prevalence rate of knee pain in the elderly. In a narrative review, Peat et al (2001) suggested that rates in the UK were between 13% and 28%, with the variation being clarified by differences in study group design, survey methods, case definitions and the inclusion of questions. Furthermore, a recent community survey (with 6792 respondents) in the UK general population reported that 46.8% of people aged 50+ years had complained of knee pain in the last 12 months; of these, 33% consulted their GP (Jinks et al 2004). Although there are several theories regarding the etiology of osteoarthritis in the knee, it is known that there is a higher incidence in women than men (Lachance et al 2002). There is also a higher incidence of the development and progression of osteoarthritis in the knee associated with obesity and an increase in the need for total knee replacements (Messier et al 2000, Christensen et al 2005).
Synovial folds within the knee (called plicae or synovial plicae) can sometimes be symptomatic. These are caused by embryonic folds that separate the knee into compartments that normally disappear after birth, but occasionally they remain and will not be noticed until an arthroscopy is performed on the knee (Boles & Martin 2001, Kim et al 2006, Nakayama et al 2011). Occasionally, a plica may become aggravated, thickened and inflamed, normally associated with repetitive movement and strain (Duri et al 2002, Cothran et al 2003, Christoforakis et al 2006), and develop into ‘plica syndrome’ (Dupont 1997, Schindler 2004, Demirag et al 2006). Plica is not generally listed as a common condition that affects the knee because it can be very difficult to clinically differentially diagnose it from other intra-articular conditions, such as damage to the articular cartilage or meniscus or osteochondritic changes to the knee (Fulkerson et al 2004, Christoforakis et al 2006, Kent & Khanduja 2010). In addition, although manual therapy can be effective in treating the symptoms of plica, in most circumstances the best treatment for knee plica is arthroscopy (Williams et al 2012, Schindler 2014, Vassiou et al 2015). Table 13.4 lists some common disorders of the knee.
Knee injuries
In athletes of various sports, the knee joint is the most common part of the body to be injured. According to a US epidemiological review, the incidence of knee injuries in patients presenting to the emergency departments was 2.29 per 1000 people (Gage et al 2012). Among all knee injuries, ligament injuries and meniscal tears are the most common, and they account for about 40% and 11% of all knee injuries, respectively (Nicholl et al 1991). Of the ligaments of the knee, the anterior cruciate and medial collateral ligaments are the most frequently injured, accounting for about 49% and 29% of all ligament injuries, respectively (Miyasaka et al 1991). The patellofemoral joint is also vulnerable and it can account for 25–40% of knee symptoms in active individuals (Boling et al 2010, Lankhorst et al 2012).
Knee examination
Medical history
A detailed medical history of the patient should be taken to help identify the red flags, characterize the severity of the pain, and facilitate the physical examination. The examiner should ask the patient presenting with knee pathology whether there is a history of trauma. If there is, the patient should be asked to discuss the history of the pain or injury (e.g. severity and type of pain, behavior since onset, history of swelling, duration of symptoms, and exacerbating and relieving factors).
If there is no history of trauma, other possible causes and risk factors should be taken into consideration, such as the patient’s age, sex, weight and level of physical activity. Apart from questioning about pain, history of trauma or other issues related to the knee, the examiner should also find out whether the knee gives way or locks. If any of these symptoms is present in the patient, it indicates a possible meniscus injury.
Red flags
Table 13.5 summarizes red flag conditions of the knee.
Physical examination
The physical examination of the knee is considered crucial from several aspects: it helps confirm initial findings, fully explore the nature and extent of the problem, and make judgments. A general evaluation of the knee involves inspection, palpation, range of motion and a variety of special tests.
Inspection
A careful visual inspection of the patient’s knee should be performed to compare the affected knee with the asymptomatic knee, and identify redness, swelling, bruising, deformity or skin changes. The examiner should start by observing movements of the knee during rising from a chair and standing, walking and in a sitting position. Any abnormalities observed, such as unusual ligamentary laxity, genu recurvatum, genu varus, genu valgum and flexion deformity, should be noted immediately.
Condition | Signs and symptoms |
Knee fractures | History of recent trauma such as a knee injury or a fall from height Pain, bruising or swelling on the affected leg Numbness, tingling, or a pins-and-needles sensation Difficulty in bending the knee Inability to walk or bear weight on the involved leg |
Compartment syndrome | History of trauma Severe, persistent pain and hardness to anterior compartment of shin Pain intensified with stretch applied to affected muscles |
Extensor mechanism disruption | Ruptured quadriceps or patella tendon Altered position of the patella (superior translation) |
Septic arthritis | Fever, chills Recent bacterial infection, surgery or injection Severe, constant pain Systemically unwell such as unusual fatigue (malaise) or loss of appetite Coexisting immunosuppressive disorder Red, swollen joint with no history of trauma |
Cancer | Unremitting pain Previous history of cancer Atypical symptoms with no history of a trauma Systemic symptoms such as fever, chills, malaise and weakness Unexplained weight loss Suspected malignancy or unexplained deformity, mass or swelling |
