Knee Osteoarthritis

Description of Knee Osteoarthritis


According to JAMA more than 10 million Americans are affected with knee osteoarthritis.[1]Most commonly affecting a population age 45 and greater this condition occurs as the cartilage in the knee wears away eventually causing bone on bone contact between joint surfaces. Most common complaints include joint swelling, joint stiffness, and pain. Knee osteoarthritis can be diagnosis via radiographs indicating boney cysts, narrowing joint space, and scelrosing of the bone.

A 2017 review into reasons for the increased prevalence of knee OA reported that the recent increase in knee OA levels cannot simply be considered an inevitable consequence of people living longer. Iinstead is the result of modifiable risk factors, including but not limited to high BMI, that have become more common since the mid-20th century. From an evolutionary perspective, knee OA thus fits the criteria of a “mismatch disease” that is more prevalent or severe because our bodies are inadequately or imperfectly adapted to modern environments.[2]

Knee osteoarthritis is the occurrence of osteoarthritis(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.”[3]

Osteoarthritis involves the degradation of joints, including: articular cartilage; subchondral bone; ligaments; the capsule and the synovial membrane. This eventually leads to pain and loss of function.[4]

Osteoarthritis is the most common disease of joints adults suffer from worldwide.


Anatomy and Pathological Process

The knee joint consists of both approximation of the proximal tibia and the distal end of the femur. The cartilage located on the ends of the femur and tibia contain an extra cellular matrix that contains type 2 protoglycans that function by drawing fluid into the joint causing increased shock absorption and proper joint nutrition.[6] There is some evidence to support that as the ageing process occurs the type 2 collagen fibers decrease in size and therefore less fluid an nutrition gets into the joint surfaces eventually leading to decreased protection along boney surfaces.

The knee (art. genus) is a synovial joint, which consists of 3 articulations. The primary joint, art. tibiofemoral, is located between the convex femoral condyles and the concave tibial condyles.[7] 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.[3]

“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)[8] 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.[9][10]

Not only the cartilage can be affected, there can also occur laxity of the ligaments and muscle atrophy. [11] [12]


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.[4] “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).” [13]

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).” [13] 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. [13]

Age is not the only factor that plays a role in the evolution of OA. Other risk factors are[14]:

  • Obesity & BMI.png
  • 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.[14]

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.[15]


Knee oa.jpg

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. The image shows that the medial joint space is more narrow than the lateral joint space.[14]

Differential Diagnosis

Bursitis; Iliotibial band syndrome; ligamentous instability (medial and lateral collateral ligaments); Meniscal pathology; Gout and Pseudogout; Rheumatoid arthritis; Septic arthritis.[1][16]


Primary[17]:More commonly diagnosed[14]

Secondary: This type of OA can be caused by obesity, trauma, inflammatory or genetically[14]

  • Loss of mobility in the affected joint
  • Decrease in muscle power
  • Instability of the joint
  • Crepitations

Diagnostic Procedures

Physical Examination

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.

Diagnostic Tests

Blood Tests; to help determine the type of arthritis

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.

MRI. Magnetic resonance imaging (MRI) does not use radiation but is more expensive than X-rays. Provides a view that offers better images of cartilage and other structures to detect early abnormalities typical of osteoarthritis[18].

Physical Therapy Management

Exercise Bike.gif

Physical therapy can be your first line of defence for managing knee OA symptoms. Pain is a common symptom that occurs in many levels (e.g. mild, moderate and severe). Exercises[19] have been proven to be effective as pain management and also improving physical functioning (e.g. muscle strengthening and aerobic condition) on short term.[14]  In order to perform it correctly, exercises have to take place under the supervision of a health care professional such as a physiotherapist. When properly instructed these exercises can be performed at home, though research has shown that group exercise combined with home exercise is more effective.[20]  Aerobic walking, strengthening of the quadriceps, resistance training and tai chi are a few examples of exercises that can be efficacious for knee OA patients.[14]

The main goals of physiotherapy for knee arthritis

  • Reduce knee pain and inflammation.
  • Normalise knee joint range of motion.
  • Strengthen lower kinetic chain: esp quadriceps (esp VMO) and hamstrings, and including calves, hip and pelvis muscles.
  • Improve your patellofemoral alignment and function.
  • Normalise muscle length via stretching and mobilisations.
  • Improve proprioception, agility and balance.
  • Improve function eg walking, squatting.
  • educate regarding activity modification, if necessary.
  • educate regarding weight loss (if appropriate) and general fitness/exercise.
  • teach in use of gait aide of appropriate.

Land based exercises are ideal for most clients. Strongly recommend by guidelines[21] for knee OA, land based exercises are appropriate for all clients regardless of their age, structural disease severity, functional status or pain levels. Exercise has also been found to be beneficial for other comorbidities and overall health. Walking, muscle-strengthening exercise, stationary cycling, Hatha yoga and Tai Chi are examples of such exercises. Individualised exercise program are always the best, taking into account account the person’s preference, capability, and the availability of resources and local facilities. Realistic goals should be set. Dosage should be progressed with full consideration given to the frequency, duration and intensity of exercise sessions, number of sessions, and the period over which sessions should occur. Attention should be paid to strategies to optimise adherence.

The video below gives 5 good home exercises for people with knee osteoarthritis.


When being treated, other aspects such as self-management and education, are of crucial importance as well.[19] There are various forms of therapeutic interventions that may or may not be helpful for patients with knee OA as listed in the guidelines and include: Hydrotherapy; manual therapy; massage therapy; thermotherapy; electrotherapy; ultrasound; bracing; surgery and postoperative exercises. See table below.


Is a non-invasive and non-interventional therapeutic intervention that is recommended in international guidelines.[14] Although there is some contradictory evidence hydrotherapy can be useful in cases where pain is too grave to exercise on dry land. Many consider water-based exercises as a good preparation of exercise ashore. [23] 

Knee osteoarthritis mostly affects the weight-bearing joints and leads, amongst other things, to pain and muscle weakness. 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).[24]  , [25].[25] It has been shown that water buoyancy can reduce the weight that joints, bones and muscles have to carry.[26] Range of motion can also be maintained and increased[25]using the freedom of movement offered by the water with the support given by the buoyancy.

Functional difficulties of osteoarthritis patients are generally walking and climbing stairs and much can be done to re-educate such patients in the pool.[25]. Many patients are more mobile in water than on land and this gives them greater confidence and a sense of achievement.

Examples of hydrotherapeutic exercises:

  • Stretching
  • Muscle strengthening
  • Aerobics

Despite the controversy, other studies show that aquatic exercises (Aquatherapy) have some short-term beneficial effects.[27]. Thus, the results indicate that hydrotherapy is applicable and efficient for patients with knee OA. Though there are short-term effects, long-term effects have yet to be investigated.[26] Aquatic exercise may therefore be considered as the first part of an exercise therapy program to get particularly disabled patients introduced to training.[27]

Manual therapy

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. One study proved that manual therapy can relieve pain and decrease stiffness.[28]

Massage therapy

Until recently massage has been proven not to be effective in the case of osteoarthritis. One study has shown that this therapeutic intervention, which uses both Swedish (including effleurage, pétrissage, fricition, tapotement and vibration) and the standard massage technique is safe, reduces pain and improves function.[29]


Contrary to heat application, which did not have significant effects, ice massage and packs have showed to improve both ROM (range of motion) and physical function. Whether ice packs relieve pain is still unknown, thus further investigation is needed.[30]


Transcutaneous electrical nerve stimulation is an example of electrotherapy, which has beneficial effects on relieving pain and improving physical function.[14], [31]TENS is a stimulation that uses electrical currents, which are applied directly to the skin and surrounding the knee.[14] Despite the positive effects, electro stimulation is not effective on improving strengthening of the quadriceps.[27] 


Older studies have claimed that this therapeutic option is not beneficial in the treatment of knee osteoarthritis. However, newer studies have shown that ultrasound reduces pain and improves the aerobic condition.[31], [32]

External Support Devices


Knee braces are used as a therapeutic procedure for patients with OA that involves the medial and lateral tibiofemoral compartments. Their purpose is to diminish the articular contact stress in those compartments. There are various types of braces [14]

  1. “Rest” braces: are not advised due to weakening of the quadriceps muscle.
  2. Knee sleeves: maintain warmth and (mild) compression.
  3. Corrective braces: used by patients with moderate or severe knee OA. They provide and reduce compression of the joint and improve proprioception and strengthening of the quadriceps.


Has proven to be slightly effective in decreasing pain and disability for patients with knee OA.[24] These beneficial effects are short-termed.

Surgery and   post-operative   exercise

Surgery is only recommended when therapies are not effective. There are various types of knee OA surgery[14]:

  1. Arthroscopic surgery: Damaged cartilage will be removed. It only has short-term effects.
  2. Knee replacement surgery: It is proven to reduce pain and increase the mobility. This type of surgery has long-term beneficial effects.

Post- operative exercises are very much recommended. Exercises to improve the function of the new joint and muscle strengthening are most effective.[20]

Medical Management

The main goal of any therapy for patients with knee OA in most cases is to reduce pain and improve the physical functioning. [19]

Although pharmacological treatment is not proven to have outcomes that are of crucial importance and despite its controversy, medications are often recommended by doctors.[14] Medicines that are primarily used by patients with knee OA, with or without co-morbidities[19]:


A pain and fever relieving OTC* drug. Because of its safety and mild effectiveness, it is one of the most used oral medicine.[33] It is also proven to be effective when acetaminophen can be combined with other drugs, e.g. ibuprofen, both with lower doses.[34] 

If there isn’t any significant or positive response to the use of acetaminophen, NSAID is then recommended. NSAIDs are primarily used for joint pain.[34]  Despite its common use, the consumption of this drug should be limited to short-tem, in order to control episodic painful flares[33]and to prevent other side effects, such as myocardial infarction and stroke.

There are two forms of Nonsteroidal inflammatory drugs

  1. Oral NSAIDs
  2. Topical NSAIDs

Both forms are advised to contain cyclooxygenase 1 and 2 (COX-1 and COX-2) inhibitors, which help in gastric mucosa protection.

When there is a lack of reaction to NSAIDs, opioids are used. Both Tramadol and codeine contain opioids, which are refractory pain relieving medicines that are generally used for the treatment of moderate to severe knee OA.[33],[34]
  Intra-articular injections
Pain relieving fluids that are consumed if opioids aren’t sufficient. They are directly injected into the arthritic joint of the knee in full extension.[34] Hyaluronic acid and corticosteroids are examples of injected fluids.
  • OTC= Over-the-counter drug

Patients have to be prudent when taking medicines. All drugs have side effects, some more than other, thus it is very important that patients with other health issues verify if they may use a particular medication. Cardiovascular gastrointestinal are the most common side effects.

Some medications are not recommended for patients with OA, due to their unproven benefit or negative reactions:[33], [34] 

  Glucosamine sulfate and chondroitin sulfate
Glucosamine is a much used drug. Because of their lack of benefit, they are not recommended; ditto for chondroitin sulfate.[34]
  Topical capsaicin
Topical capsaicin creams contain extracts of chili pepper that activate a burning sensation.[34] Although many studies do not recommend those creams, other report that it is effective.

Knee Arthritis Injections/Surgery

  • In some cases, patients with knee arthritis choose to undergo knee surgery for knee arthritis. The most common forms of surgery for this condition are Therapeutic Injections, arthroscopes, partial or total knee replacements.
  • If symptoms are reaching an unmanageable level and treatment results have plateaued surgical options may be of benefit.
The below video gives a good guide to both surgical and non surgical options and why or when they are offered.

Conservative Treatment

Ottawa Panel of evidence suggests the use of therapeutic exercises or exercises with manual therapy to be most beneficial for patients with knee OA. [36] Cliborne et al. found short term benefits with hip mobilizations to decrease knee pain with functional tests including squatting.[37]  Another article by Currier et al. developed a CPR for patients with knee pain to indicate those patients have knee OA, and which patients are likely to have short term benefits from hip mobilizations. Currier reports the “5 clinical prediction rules for this study include: 1. hip and groin parasthesia 2. groin pain 3.passive knee flexion less than 122 degrees 4.passive hip IR less than 17 degrees 5.Pain with hip distraction”.[38] If the patient has 2 variables then the positive likely hood ratio is 12.9. Deyle et al. found that knee mobilization gave statically improvements in WOMAC and 6 minute walk tests for both 4 week, 8 week, and 1 year follow up.[39]


A 2018 review[40] concluded nicely on the state of current management of knee osteoarthritis and I quote

"Despite being one of the most studied and more prevalent conditions of our population, knee osteoarthritis still does not have a clear pathophysiology or a single most efficacious intervention to treat the symptoms and degeneration associated. Exercises in early stages are a valuable therapy for these patients and it is recommended by all the medical societies. Other non-surgical treatments have variable efficacy and their success will depend on multiple variables (provider, equipment, patient) and their use has to be selected judiciously according to the specific clinical situation."

Also it noted that  although multiple therapies have been studied in the past, low impact physical activity seems to be supported by all the current medical societies while other interventions have shown conflicting findings.


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