Dr. de Barutell, a renowned specialist in Pain Unit, Anesthesiology and Resuscitation, explains the available treatment pathways to address knee osteoarthritis. The doctor was the founder of the Pain Clinic of the Vall d’Hebron Hospital, the first Pain Clinic in Catalonia and the second in Spain. He is currently co-director of the Pain Clinic Hospital El Pilar.
The knee joint is the largest synovial joint of the human body, allowing the extension and flexion movements of the leg, while it must provide good stability and resistance to the weight to be supported, as well as sufficient mobility to move it.
It consists of three joints: two femototibial joints, which are those that transfer body weight to the legs, between the femoral and tibial condyles, and a femoropatellar joint between the patella and femur.
There are also two menisci, external and internal, between the femur and the knee, which cushion the articular surfaces during movement. The joint is reinforced by extracapsular ligaments that stabilize the hinge motion of the knee (internal lateral, external lateral, patellar, popliteal oblique and popliteal arcuate) and intracapsular ligaments that maintain contact of the articular surfaces during knee flexion (anterior and posterior cruciate ligament). All articular surfaces not covered by articular cartilage are lined by the synovial membrane, with several synovial pouches.
Knee osteoarthritis: what is it and how does it manifest itself?
Knee osteoarthritis is a chronic disease of very high prevalence in adults over 45 years of age, being more prevalent in women than in men.
It is characterized by mechanical pain, functional impairment, joint instability and periarticular muscle weakness. Onset is usually insidious, with episodes of pain increasing in frequency and duration. When joint damage is severe, continuous pain appears in some patients. Pain and stiffness are localized at the joint level and are not accompanied by general symptoms. Morning stiffness after rest is usually brief and localized. The mechanisms that may cause pain are: increased intracapsular and intraosseous pressure, subchondral microfractures, tendon involvement or bursitis secondary to muscle weakness and injuries of articular structures.
On examination, pain on passive movements and crepitus of the articular structures may be observed. In advanced osteoarthritis, some degree of joint instability and deformity due to the formation of juxta-articular osteophytes can be seen.
How osteoarthritis of the knee is diagnosed and imaging tests
The diagnosis is reached, as a general rule, by physical examination and the findings of simple radiology although, on occasions, it can happen that a patient has intense pain that does not correlate with the radiological findings, due to the existence of superimposed lesions, such as meniscal rupture. It is also frequent that patients with radiological alterations of osteoarthritis are asymptomatic. Therefore, therapeutic decisions, especially surgical ones, should always be based on the joint functional stage and on the repercussions of pain on the patient’s activities, and not on imaging tests.
The classic radiological findings of osteoarthritis are: osteophytes, joint space pinching, subchondral sclerosis, geodes and joint subluxations. Likewise, magnetic resonance imaging (MRI) is currently the technique with the greatest diagnostic capacity in the field of musculoskeletal radiology, since it allows bone, joint and soft tissue studies. Therefore, it can be considered the technique of choice after a conventional radiological study. MRI allows a sensitive and reproducible quantification of cartilage loss in osteoarthritis.
Treatments available for osteoarthritis of the knee
The treatment of osteoarthritis of the knee will be individualized by the specialist in the Pain Unit. A non-pharmacological approach is considered essential, including patient education, weight control and rehabilitation exercises appropriate to each patient, especially to strengthen the quadriceps. A wide pharmacological arsenal is also currently available with anti-inflammatory drugs (NSAIDs) and, ultimately, opioids.
Intra-articular knee block or infiltration is a therapeutic modality to be taken into account in osteoarthritis of the knee joint. It generally achieves a great relief of the symptomatology, with few side effects, being a complementary or alternative treatment to others. Joint infiltration can be performed with different drugs: corticosteroids, local anesthetics, hyaluronic acid and platelet-rich plasma and growth factors. These are detailed below:
– Intra-articular application of corticosteroids→ Requires delayed formulations, the most indicated being triamcinolone acetonide. They exert their effect quickly, are reliable and have few side effects. It is not advisable to repeat more than four infiltrations in the same joint and they should be separated by more than one week between them. However, they are not free of risks such as post-injection pain, tendon rupture, microcrystal arthritis and joint infection.
– Local anesthetics→ They can be used alone but are usually mixed with corticosteroids to decrease the occurrence of microcrystal arthritis while producing early relief of symptoms.
– Hyaluronic acid (HA)→ A natural component of the matrix of connective tissue and synovial fluid in joints. The basis of its use lies in the attempt to improve joint biomechanics altered in osteoarthritis. It exerts a reparative action on viscoelasticity and restorative action on joint lubricating function. Currently, there are multiple preparations of high or low molecular weight in pre-filled syringes of 3 to 5 doses that are administered weekly. There are also unidosis preparations (for a single injection) with higher doses, which is the one we usually use. They can be effective in improving pain and joint function within 6-8 months, although it depends on several factors, such as the patient’s age, severity of the disease and its duration.
– Platelet-rich plasma and growth factors→ This is an autologous blood product with a high platelet content, resulting from the centrifugation of a blood sample. When injected into the joint, platelet-derived growth factors are provided and facilitate improvement of the disease. The hyaline articular cartilage of the knee is an avascular, aneural and alymphatic tissue, with little possibility of healing on its own, due to its low cellular population. The application of platelet-rich plasma helps in the repair of this tissue damage, especially in the early stages of the disease.
If all these treatments do not give the expected result, joint replacement surgery can always be resorted to.