Knee Osteoarthritis

Original Editors - Fien Selderslaghs, Laura Van Der Perren, Mirabella Smolders, Liese Magnus

Top Contributors - Mirabella Smolders, Laura Van Der Perren, Hamelryck Sascha, Abbey Wright, Laura Ritchie, Lucinda hampton, Kim Jackson, Jessica Davis, Fien Selderslaghs, Venugopal Pawar, Rachael Lowe, Bo Hellinckx, Vidya Acharya, Admin, Ophélie Schraepen, Candace Goh, 127.0.0.1, Feebe Robyns, Joni Roesems, Jelien Wouters, Evan Thomas, Anthony Mertens, Rucha Gadgil, Michelle Lee, Barb Clemes, Jess Bell, Kai A. Sigel, Sai Kripa, WikiSysop, Aminat Abolade, Simisola Ajeyalemi, Robin Tacchetti, Rishika Babburu and Arthur Devoldere

Introduction

Knee osteoarthritis (OA), also known as degenerative joint disease, is typically the result of wear and tear and progressive loss of articular cartilage. It is most common in elderly people and can be divided into two types, primary and secondary:

• Primary osteoarthritis - is articular degeneration without any apparent underlying cause.
• Secondary osteoarthritis - is the consequence of either an abnormal concentration of force across the joint as with post-traumatic causes or abnormal articular cartilage, such as rheumatoid arthritis (RA).

Osteoarthritis is typically a progressive disease that may eventually lead to disability. The intensity of the clinical symptoms may vary from each individual. However, they typically become more severe, more frequent, and more debilitating over time. The rate of progression also varies for each individual.

Common clinical symptoms include

• Knee pain that is gradual in onset and worse with activity,
• Knee stiffness and swelling,
• Pain after prolonged sitting or resting.

Treatment for knee osteoarthritis begins with conservative methods and progresses to surgical treatment options when conservative treatment fails. While medications can help slow the progression of RA and other inflammatory conditions, no proven disease-modifying agents for the treatment of knee osteoarthritis currently.

Epidemiology

OA is the most common disease of the joints worldwide, with the knee being the most commonly affected joint in the body. It mainly affects people over the age of 45.

OA can lead to pain and loss of function, but not everyone with radiographic findings of knee OA will be symptomatic: in one study only 15% of patients with radiographic findings of knee OA were symptomatic.

• OA affects nearly 6% of all adults
• Women are more commonly affected than men
• Roughly 13% of women and 10% of men 60 years and older have symptomatic knee osteoarthritis.
• Among those older than 70 years of age, the prevalence rises to as high as 40%.
• Prevalence will continue to increase as life expectancy and obesity rises.

Etiology

Knee OA is classified as either primary or secondary, depending on its cause:

1. Primary knee OA is the result of articular cartilage degeneration without any known reason. This is typically thought of as degeneration due to age as well as wear and tear.
2. Secondary knee OA is the result of articular cartilage degeneration due to a known reason. Possible Causes of Secondary Knee OA:

• • Obesity
  • Joint hypermobility or instability
  • Malpositioning of the joint e.g. valgus/varus posture
  • Previous injury to the joint e.g. fracture along articular surface (tibial plateau fracture)
  • Congenital defects
  • Immobilisation and loss of mobility
  • Family history
  • Metabolic causes e.g. rickets

Relevant Anatomy

The knee (art. genus) is a synovial joint, which consists of 2 articulations.

• Tibiofemoral joint is located between the convex femoral condyles and the concave tibial condyles (the primary joint).
• Patellofemoral joint between the Femur and the Patella

OA can occur in either or both of these articulations of the knee, it is usual that the patellofemoral joint is affected first.

Pathological Process

The process of osteoarthritis affects the articular cartilage (mainly type II) that covers the articular surfaces of bone.

Articular cartilage is normally maintained in a healthy equilibrium of chemical reactions, however, when OA starts to develop the reactions are disrupted leading to changes in the collagen of the cartilage:

1. Disruption in the equilibrium which results in the disorganised pattern of collagen, and loss of articular cartilage elasticity.
2. This results in cracking and fissuring of the cartilage which leads to erosion of the articular surface.
3. Cartilage that has been damaged, cannot recover.
4. The cartilage will continue to wear away
5. Once the cartilage has worn away; bony surfaces will start to be affected
6. The bone will expand and spurs (osteophytes) will develop.

It is common for ligament laxity and muscle atrophy to also occur as the disease progresses.

Characteristics/Clinical Presentation

Signs of knee OA are:

• Pain on movement
• Stiffness, particularly early morning stiffness
• Loss of range of movement
• Pain after prolonged sitting or lying
• Pain on joint line palpation
• Joint enlargement.
  

We can subdivide knee OA in 5 grades:

• Grade 0: This is the “normal” knee health
• Grade 1: Very minor bone spur growth and is not experiencing any pain or discomfort.
• Grade 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.
• Grade 3: Moderate OA. Frequent pain during movement, 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.
• Grade 4: This is the most severe stage of OA. The joint space between the bones will be dramatically reduced, the cartilage will almost be completely gone and the synovial fluid will be decreased. This stage is normally associated with high levels pain and discomfort during walking or moving the joint.

Diagnosis

Image 2: medial joint space is more narrow than the lateral joint space

The diagnosis can be established by clinical examination, and it can be confirmed by X-rays.

Diagnostic Tests

Blood Tests; to help determine the type of arthritis

Physical examination: see below

X-ray: A 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 OA.

MRI. Magnetic resonance imaging (MRI). Provides a view that offers better images of cartilage and other structures to detect early abnormalities typical of osteoarthritis.

Radiographic Findings of OA

• Joint space narrowing
• Osteophyte formation
• Subchondral sclerosis
• Subchondral cysts
• Early stages of OA shows a minimal unequal joint space narrowing.
• In severe OA the joint line may disappear completely (see image 2).

Treatment/Management

Treatment for knee OA can be broken down into conservative and surgical management.

Initial treatment always begins with conservative modalities and moves to surgical treatment once conservative management has been exhausted. There is a wide range of conservative modalities is available for the treatment of knee OA. These interventions do not alter the underlying disease process, but their goal is to reduce pain and optimise function for as long as possible.

Conservative Treatment Options

The primary treatment for OA knee conservatively is exercise therapy within physiotherapy. Physiotherapy normally involves

• Patient education
• Exercise therapy
• Activity modification
• Advice on weight loss
• Knee bracing

• • The first-line treatment for all patients with symptomatic knee osteoarthritis includes patient education and physiotherapy. A combination of supervised exercises and a home exercise program have been shown to have the best results. These benefits are lost after 6 months if the exercises are stopped.
  • Weight loss is valuable in all stages of knee OA. It is indicated in patients with symptomatic OA with a body mass index greater than 25. The best recommendation to achieve weight loss is with diet control and low-impact aerobic exercise.
  • Knee bracing in OA can be used. Offloading-type braces which shift the load away from the involved knee compartment. This can be effective when there is a valgus or varus deformity.

Other non-physiotherapy based interventions include pharmacological management:

• Acetaminophen
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• COX-2 inhibitors
• Glucosamine and chondroitin sulfate
• Corticosteroid injections
• Hyaluronic acid (HA)

• • Drug therapy alongside physiotherapy should be the first-line treatment for patients with symptomatic OA. There are a wide variety of NSAIDs available, however, caution should be used when prescribing NSAIDs due to their side effects.
  • Glucosamine and chondroitin sulfate are available as dietary supplements. They are structural components of articular cartilage, and the thought is that a supplement will aid in the health of articular cartilage. No strong evidence exists that these supplements are beneficial in knee OA.
  • Intra-articular corticosteroid injections may be useful for symptomatic knee OA.
  • Intra-articular hyaluronic acid injections (HA) injections are another inject-able option. Local delivery of HA into the joint acts as a lubricant and may help increase the natural production of HA in the joint.

Differential Diagnosis

• Meniscal pathology
• Patellar-femoral pain syndrome
• Gout and Pseudogout
• Rheumatoid arthritis
• Septic arthritis
• Hip OA
• Referred lower back pain
• Ligament injury ACL or PCL rupture

Subjective assessment

Take a proper history of pain including when the pain started if it was gradual or sudden, if there was any previous injury to the same knee.

The common subjective symptoms of knee OA are:

• Early morning stiffness
• Dull achy pain
• Pain after sitting
• Pain after increased activity
• Reduced mobility
• Difficulty weight bearing on the affected leg
• Decrease in the abilities of daily functioning
• Sleep may be affected (screen red flags appropriately)

Objective assessment:

After a thorough subjective assessment it may be clear the diagnosis of the patient already, however, it is always necessary to perform an objective assessment to rule out differential diagnoses and provide objective outcome measures such as range of movement (ROM).

• Observation of the knee: it may be enlarged, swollen or red if the OA is very reactive or irritated.
• Observation in general: movement patterns at rest and when performing simulations of daily activities such as getting up from and down on a chair
• Gait assessment: use of walking aids may be required due to pain, is there any stiffness during gait, is there significant reduced weight bearing of the affected knee.
• Palpation: swelling, temperature changes, joint line tenderness may all be present in an acutely aggravated OA knee
• ROM: flexion and extension may be limited due to stiffness or formation of osteophytes in the joint
• Strength: reduced strength is normal in an OA knee due to pain and deconditioning
• Normal functional activities: such as climbing stairs may be affected
• Balance: may be affected due to pain, this needs to be assessed to rule out falls risk.

Physiotherapy Management

Physiotherapy should be started with all patients with a diagnosis of OA.

Pain is a common symptom that occurs at different intensities depending on the individual, it is not necessarily related to severity of OA progression.

Exercise has been proven to be effective as pain management and also improves physical functioning in the short term. Exercises have to take place under the supervision of a physiotherapist initially and when properly instructed these exercises can be performed at home, though research has shown that group exercise combined with home exercise is more effective.  

Role of Physiotherapy

Education:

• Understanding what OA is
• Explaining pain
• Explain long term management of OA
• Educate regarding activity modification
• Role of weight loss
• Promote active, healthy lifestyle

Exercise:

• Reduce knee pain and inflammation.
• Normalise knee joint range of motion.
• Strengthen lower kinetic chain
• Cardio-vascular exercise
• Improve proprioception, agility and balance.
• Improve function
• Use of walking aids as needed

Land-based exercises are ideal for most people and are strongly recommended.

Exercise has also been found to be beneficial for other co-morbidities and overall health. Walking, resistance training, cycling, yoga and Tai Chi are examples of such exercises. An individualised exercise program should be set by a physiotherapist initially, taking into account the patient's goals and hobbies to ensure long term exercise compliance.

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

Other interventions:

There are various forms of therapeutic interventions that may or may not be helpful for patients with various degrees of evidence to support them:

• Hydrotherapy - this may be particularly helpful if pain is very high and analgesia is not tolerated. It can be useful to build up strength and reduce stiffness around the knee joint in a non-weight bearing position.
• Taping - works to offload the joint similar to bracing, this is useful in the short term.
• Manual therapy - effective to improve ROM
• Massage - may be useful to control pain in some subjects, but this has low evidence to show its effectiveness
• Bracing
• Electrotherapy - such as TENS and muscle stimulation may be used to improve quadricep strength and has some evidence to show it can help with pain reduction.

Medical Management

If conservative management is not sufficient at controlling pain, surgical interventions can be explored.The most common forms of surgery for this condition are (from least to most invasive):

• Therapeutic Injections
• Arthroscopy - with the goal to remove osteophytes and any degenerative meniscal tears (this should not be considered if no osteophytes are present on XR)
• High tibial Osteotomy - if the patient meets the pre-operative functional level
• Patellofemoral joint arthroplasty - if only the patellofemoral joint is affected, and tibiofemoral joints are healthy
• Unicompartmental knee arthroplasty - if only one compartment (medial or lateral) is affected
• Total knee replacements

The below video gives a good guide to both surgical and non surgical options and why or when they are offered.

Conclusion

Knee OA is best managed initially by conservative management. Failing this intervention and with positive radiographic evidence of OA surgical options can be considered to reduce pain in the long term and improve quality of life.

• OA has no cure and thus attempts should be made to prevent progression of the disease.
• Treatment for knee OA begins with conservative methods and progresses to surgical treatment options when conservative treatment fails.
• A multi-disciplinary team approach should be taken to promote healthy lifestyle and control pain i.e. physiotherapist, dietitian and pharmacist
• Orthopaedic specialists should be referred to if pain becomes unmanageable.