Knee Osteoarthritis

Original Editors - Fien Selderslaghs

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Search Strategy

Databases used: Pubmed, Web of knowledge, American college of rheumatology.

Keywords used: osteoarthritis, knee, epidemiology, etiology, treatment, definition, exercises, surgery, condition (or a combination of these words).

Definition/Description

Knee osteoarthritis is the occurrence of osteoarthritis(A) (OA) in the knee joint. Osteoarthritis has many definitions, but Kuttner et al . defined it as follows: “Osteoarthritis, also known as degenerative arthritis or degenerative joint disease, is a group of overlapping distinct diseases, which may have different etiologies but with similar biologic, morphologic, and clinical outcomes.”12

In other words osteoarthritis involves the degradation of joints, including articular cartilage and subchondral bone. But also ligaments, the capsule and the synovial membrane degenerate. This will eventually lead to pain and loss of function.11

Osteoarthritis is the most common disease of joints adults suffer from worldwide. The name ‘osteoarthritis’, a Greek word, can be divided in ‘osteo’, ‘arthro’ and ‘it is’. If we translate the word we become ‘of the bone’, ‘joint’ and ‘inflammation’.10 Thus, simply put, we can say that osteoarthritis is an inflammation of the bone and joint. Besides knee osteoarthritis, which is the most common, you also have hand and hip osteoarthritis.

Clinically Relevant Anatomy

The knee (art. genus) is a synovial joint, which consists of 3 articulations. The primary joint, art. tibiofibularis, is located between the convex femoral condyles and the concave tibial condyles.[13] There is also the art. patellofemoralis between the femur and the patella and the art. tibiofibularis located between the tibia and fibula. OA can only occur in the two primary articulations of the knee, namely the tibiofemoral and patellofemoral joint, because they have to sustain more motion than the art. tibiofibularis.[12]

“The pathogenesis of knee OA have been linked to biomechanical and biochemical changes in the cartilage of the knee joint.” (Kirstin Uth et al, 2014)[16] The cartilage ensures that the bone surfaces can move painless and with low friction to each other. In OA, the cartilage decreases in thickness and quality, it becomes thinner and softer, cracks may occur and it will eventually crumble off. Cartilage that has been damaged, cannot recover. Finally the cartilage will disappear. The bone surfaces can also be affected, the bone will expand and spurs (osteophytes) will develop.[17] [18]

Not only the cartilage can be affected, there can also occur laxity of the ligaments and muscle atrophy.

Epidemiology /Etiology

Osteoarthritis is the most prevalent form of arthritis and occurs especially in the knee joint. It affects nearly 6% of all adults, but more women are affected than men. [19] “According to a number of published reports, anywhere from 6% to over 13% of men, but between 7% and 19% of women, over 45 years of age are affected, resulting in a 45% less risk of incidence in men (Coleman, et al).” [20]

Age is a determining factor in the development of OA. “As the population ages in demographic terms, the prevalence of OA is expected to rise (Coleman, et al).” [20] From the age of 40 there is an increased risk of OA. Approximately 50% of the 65+ population are affected by OA in the knee, but it can also affect young people. [20]

Age is not the only factor that plays a role in the evolution of OA. Other risk factors are[23]:
- Obesity
- Joint hypermobility or instability
- Sport stress with high impact loading
- Repetitive knee bending or heavy weight lifting
- Specific occupations
- Peripheral neuropathy
- Injury to the joint
- History of immobilisation
- Family history

Characteristics/Clinical Presentation

Signs of knee osteoarthritis are pain at beginning of the movement, later on pain during movement and eventually permanent pain. These patients will also experience a loss of function like stiffness, decreased range of motion (ROM) and impairment in everyday activities. Other possible characteristics of knee OA are bony enlargement, crepitus, joint-line tenderness and elevated sensitivity to cold and/or damp.10

We can subdivide knee osteoarthritis in 5 stages:
- Stage 0: This is the “normal” knee health, without any pain in the joint functions.
- Stage 1: A person in this stage has very minor bone spur growth and is not experiencing any pain or discomfort.
- Stage 2: This is the stage where people will experience symptoms for the first time. They will have pain after a long day of walking and will sense a greater stiffness in the joint. It is a mild stage of the condition, but X-rays will already reveal greater bone spur growth. The cartilage will likely remain at a healthy size.
- Stage 3: Stage 3 is considered as a moderate osteoarthritis. People with this stage will experience a frequent pain during movement. The joint stiffness will also be more present, especially after sitting for long periods and in the morning. The cartilage between the bones shows obvious damage, and the space between the bones is getting smaller.
- Stage 4: This is the most severe stage of osteoarthritis. The joint space between the bones will be dramatically reduced, the cartilage will almost be completely gone and the synovial fluid will be decreased. That is why people will experience lots of pain and discomfort during walking or moving the joint.21

Differential Diagnosis

The diagnosis can be established by clinical examination, and it can be confirmed by X-rays. The main characteristics are changes in the subchondral bone, joint space narrowing, subchondral sclerosis, subchondral cyst formation and osteophytes. In early stage of osteoarthritis, the results of the radiography can show a minimal unequal joint space narrowing. If it deteriorates you still find the same problems, but the patient experiences a lateral subluxation of the tibia as well. If it deteriorates more, the joint line will disappear completely. It is shown in the picture that the medial joint space is more narrow than the lateral joint line. 10

33 (FIGUUR)

Some differential diagnosis can be: bursitis, iliotibial band syndrome, ligamentous instability (medial and lateral collateral ligaments) and meniscal pathology, these are conditions in whereby the soft tissues of the knee are affected. But also other forms of arthritis can lead to differential diagnosis of the knee, think of gout and pseudogout, rheumatoid arthritis and septic arthritis. 22

Diagnostic Procedures

Symptoms:

Primary:
- Pain
- Stiffness, particularly in the morning
- Sensitivity when kneeling or bending21
- Decrease in the abilities of daily functioning
- More commonly diagnosed10

Secondary:
- Loss of mobility in the affected joint
- Decrease in muscle power
- Instability of the joint
- Crepitations - This type of OA can be caused by obesity, trauma, inflammatory or genetically10

X-ray: The basic X-ray is used to research breakdown of cartilage, narrowing of joint space, forming of bone spurs and to exclude other causes of pain in the affected joint.

Arthrocentesis: This is a procedure which can be performed at the doctor’s office. A sterile needle is used to take samples of joint fluid which can then be examined for cartilage fragments, infection or gout.

Arthroscopy: is a surgical technique where a camera is inserted in the affected joint to obtain visual information about the damage caused to the joint by the osteoarthritis.

The European League Against Rheumatism developed diagnostic criteria for diagnosing knee osteoarthritis. The most important factors are shown in the following figure.

File:Risc factors.jpg

EULAR evidence-based recommendations for the diagnosis of knee osteoarthritis

Outcome Measures

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Examination

If a patient is referred to you by a doctor, it is most likely he performed a medical examination. It is imperative to look at his/her findings when examinating the patient.
- Inspection:
mind the position of the joints when in rest and how the patient moves. This can be accomplished by making the patient perform simulations of daily activities such as getting up from and down on a chair, stair climbing, etc.

- Palpation:
mind: swelling, temperature differences, muscle tonus. Also be wary of possible bone spurs (osteocytes) that have formed on the edge of the joint. These osteocytes are a serious indication towards osteoarthritis.

- Examination of basic functions:
Testing of muscle power, coordination, mobility, balance and also stability of the joint. These factors can be tested by active test like standing on one leg and passive manual tests. When testing stability of the joint muscle strength and proprioception are of significant importance.

Medical Management

- Anti-inflammatory medication to counter periodic inflammation
- Surgical replacement of knee joint when damage to natural structures is too grave.

Physical Therapy Management

Exercise	Has proved to be effective as pain management and improving of physical functioning on short term. However these exercises have to take place under supervision of a health care professional such as a physiotherapist. When properly instructed these exercises can be performed at home. However research has shown that group exercise combined with home exercise is more effective than home exercise alone. ,
Hydrotherapy	Is recommended in international guidelines. Despite contradictory evidence hydrotherapy can be useful in cases where pain is too grave to exercise on dry land. It can be a good preparation of exercise on dry land. Osteoarthritis usually affects the weight-bearing joints. Some of the above symptoms like muscle weakness will be present in most patients. The strength of muscles around the affected joints can be built up by graduated exercises making use of buoyancy and floats (in the later stage of the treatment). Range of motion can also be maintained and increased using the freedom of movement offered by the water with the support given by the buoyancy. Functional difficulties of osteoarthritis patients are generally concerned with walking and climbing stairs and much can be done to re-educate such patients in the pool. Many patients are more mobile in water than on land and this gives them greater confidence and a sense of achievement. Other studies show that aquatic exercise (Aquatherapy) has some short-term beneficial effects. They established that there is a positive effect on both mixed knee and hip Osteoarthritis and on knee Osteoarthritis alone at the end of an aquatic training program. Also no long-term effects have been found. Aquatic exercise may therefore be considered as the first part of an exercise therapy program tot get particularly disabled patients introduced to training.
Manual actions: Achieving a passive motion in the joint	Has proven effective to locate and eliminate factors like pain and joint immobility. However, it is only effective when combined with active exercise. This progress can enable further or advanced exercises.
Massage	Is not effective in the case of osteoarthritis.
Thermotherapy	Can be used to warm up of tissue (for example very stiff joints) before exercise.
Electrotherapy	For example electro stimulation in improving quadriceps muscle strength is not proven effective.
Ultrasound	Is not advised in the treatment of knee osteoarthritis.
External Support Devices	Braces: - total knee braces when being diagnosed with total knee   osteoarthritis - lateral elevated orthopedic sole when being diagnosed with   medial compartment knee osteoarthritis. Taping: Has proven slightly effective in decreasing pain in patients with patellofemoral osteoarthritis.
Post-operative Exercise	Is very much recommended. Exercises to improve the function of the new joint and muscle strengthening are most effective.

Key Research

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Resources

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Clinical Bottom Line

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Recent Related Research (from Pubmed)

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