Knee Osteoarthritis
Knee Osteoarthritis (OA) is the most common site for OA Global, regional, and national burden of osteoarthritis, 1990-2020 and projections to 2050: a systematic analysis for the Global Burden of Disease Study 2021 – PubMed with evidence showing symptomatic knee OA is roughly present in 240 cases per 100,000 people globally Knee Osteoarthritis – StatPearls – NCBI Bookshelf. Risk factors for developing this condition include, but are not limited to, increasing age, previous fracture, previous arthroscopy, malposition (Valgus/Varus alignment), increased BMI, genetics and underlying metabolic disease due to chronic systemic inflammation. The Role of Metabolic Syndrome in Osteoarthritis Development: Is Obesity the Key Driver? – ScienceDirect.
There are three compartments to the knee: the medial tibiofemoral compartment (MTFC), the lateral tibiofemoral compartment (LTFC) and the patella femoral compartment (PFJ). OA can affect one or a combination of these compartments, with the MTFC being the most commonly affected along with the PFJ, giving rise to symptoms. The compartmental distribution of knee osteoarthritis – a systematic review and meta-analysis – PubMed.
This condition is characterised by the gradual breakdown and destruction of the smooth articular cartilage that covers the ends of the femoral condyles and tibial plateaus. This leads to subsequent reactive bony changes in the subchondral bone, development of osteophytosis (bony spurs) and joint space loss. Ultimately resulting in pain, stiffness and functional loss for the patient.
What are the signs and symptoms?
Patients typically complain of anteromedial knee pain that is worse with activity and eases with a period of rest. Though in the early stages of OA activity may actually help ease symptoms, only with progression of the disease does joint pain and discomfort become more prevalent at rest and especially at night, stopping the patient from sleeping. The knee may appear swollen, and this may or may not be visible to the patient. Typically, a fullness to the knee is described above the kneecap or around the back of the knee as the fluid distends the suprapatellar recess or develops in a Baker’s cyst posteriorly. Patients have a stable knee but usually have a loss of range; they are symptomatic on palpation of the joint line medially and/or laterally. There is often associated pain and crepitus with compression through the PFJ due to the underlying degeneration.
Symptoms are generally slowly progressive over many months, sometimes years, but can also manifest with an acute exacerbation with declining function and progressive symptoms over a much shorter time frame. Simple activities like walking, climbing stairs and getting into and out of the car become more and more difficult for patients, driving them to seek medical input.
How is it diagnosed?
The diagnosis of knee osteoarthritis is a clinical one Diagnosis | Diagnosis | Osteoarthritis | CKS | NICE which can be made without imaging in patients over the age of 45 with activity-related knee pain and morning stiffness lasting less than 30 minutes. Imaging is reserved for atypical features but is often used in our service for prognosis but also helps guide interventional options.
The clinical symptoms have been discussed already. A simple AP and lateral view plain film X-ray are helpful at ascertaining the level of degeneration in the main tibiofemoral compartments and patella-femoral joint, respectively, with the classical radiographic features of joint space loss, sclerosis and osteophytosis (bony spurs)
MRI can be helpful if there is suspicion of concurrent intraarticular pathology, especially if there is minimal arthrosis on plain film but symptoms are persisting. Ultrasound is not usually indicated in the workup of a degenerative knee, but these changes can often be seen and, with the right clinical context, are often enough to make an initial diagnosis.
How are they treated?
Treatment options are divided into conservative and surgical.
Conservative options:
- Oral analgesia in combination with modifications of daily activities may help alleviate some of the symptoms, especially in the early stages of the disease, or allow acute exacerbations to settle down.
- Physiotherapy can be helpful in maintaining knee mobility and strengthening the surrounding musculature to reduce knee symptoms. Effects of exercise on knee osteoarthritis: A systematic review – PubMed
- An ultrasound-guided local anaesthetic and steroid injection +/- joint aspiration (removing the fluid) can be helpful at easing some of the inflammation associated with osteoarthritis. Relief is typically temporary, especially in more advanced cases of arthrosis, but can be helpful as a management strategy for patients that are currently not candidates for a knee replacement or do not want a knee replacement. Efficacy of intra-articular corticosteroid injections in knee osteoarthritis: A systematic review and meta-analysis of randomized controlled trials – PubMed They can be repeated if they are helpful, but typically a 6-monthly interval is advisable to reduce any potential risks, which will be discussed with the patient prior to proceeding.
- In less severe cases of arthrosis, an ultrasound-guided hyaluronic acid injection into the knee joint can be helpful as a potential alternative to repeated steroid injections. They have a very safe injection profile and can be very helpful in carefully selected patients. The effectiveness of hyaluronic acid intra-articular injections in managing osteoarthritic knee pain – PubMed
- A further alternative injection option for knee OA is an arthrosamid injection, which has been shown to provide longer-term relief in symptomatic knee OA at 12-month follow-up. Effectiveness and safety of polyacrylamide hydrogel injection for knee osteoarthritis: results from a 12-month follow up of an open-label study – PMC. Like other injectable options, outcomes are better with earlier joint disease. Please see our Arthrosamid page for more information.
Surgical options:
If conservative options do not provide adequate relief or if there is already substantial arthrosis on a plain film X-ray at the time of initial presentation, then there are surgical options.
- Arthroplasty (total knee replacement/unicompartmental knee replacement). For the majority of suitable patients, surgery provides excellent pain relief, improved function and enhanced quality of life. Effectiveness of Total Knee Arthroplasty on Pain Reduction and Functional Improvement in Elderly Patients: A Quasi-Experimental Study – PMC. Unicompartmental procedures are less invasive, have a shorter recovery time and show excellent outcomes in carefully selected patients. Clinical efficacy of unicompartmental knee arthroplasty on limb swelling, pain, and functional rehabilitation in knee osteoarthritis patients – PubMed
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