Understanding knee arthritis

 

By Dr S.S.Sathappan

MBChB, FRCSEd, M Med (Ortho), FRCSEd (Ortho), FAMS (Singapore)

Specialist in Adult Reconstructive Surgery and Complex Trauma

Tan Tock Seng Hospital

Singapore

Sathappan@ttsh.com.sg

 

I will be giving a short series of informative descriptions on arthritis of the knee and the treatment options that are available. The topic has been divided into three main sections:

 

(a)    Pathology of knee arthritis

(b)   Medical management of knee arthritis

(c)    Surgical management of knee arthritis

 

Pathology of knee arthritis

 
Overview

What does the term arthritis essentially mean? “Arth” refers to joints, and “itis” means inflammation. Therefore, arthritis is a generic term referring to inflammation of the joints. The knee like all joints has an essential basic structure consisting of (Fig 1):

 

(1)   Synovium: An outer lining of the knee joint responsible for secreting a lubricating fluid called synovial fluid

(2)   Cartilage: It forms the end of the femur (thigh bone) and the tibia (shin bone). This is an elastic tissue that is responsible for the shock-absorber function in the knee joint

(3)   Menisci: This is a structure unique to the knee joint and serves a similar role to cartilage

(4)   Ligaments: There are 4 main ligaments in the knee joint and they provide stability to the knee joint

(5)   Patella (knee cap): It serves as an important pulley, which serves to increase the power of the quadriceps muscle, which is essential for straightening the leg as well as for walking.

(6)   There are three main compartments in the knee: medial (inner compartment), lateral (outer ompartment) and patellofemoral (between kneecap and the thigh bone)

Fig 1
 

 

 Types of arthritis

 

There are two main types of arthritis: osteoarthritis and inflammatory arthritis. In both the final end pathological processes are similar (Fig 2). The cartilage is destroyed and result in the bone ends grinding against each other resulting in loss of mobility, deformity and dysfunction.

Fig 2
 

Osteoarthritis affects about 10% of the general population and is often secondary to degenerative processes and thus its prevalence increases with age. Inflammatory arthritis is less common and is often attributed to inflammatory processes that lead to global joint destruction. Rheumatoid arthritis would be an example of an inflammatory arthritis. In this condition there are rheumatoid factor antibodies that are released into the bloodstream which cause joint damage. Exactly why they are released into the blood stream is not clear; but the process of self-destruction has also led to the descriptive term auto-immune (“auto” = self; “immune”=mediated via the immune system) disease

 

Patient presentation

Due to the wear of the cartilage, patients often complain of pain in the knee joint. There is often exacerbation of joint inflammation resulting in knee swelling. Occasionally there are loose bodies causing joint impingement. With disease progression there is loss of joint motion and this can be associated with hamstring spasm causing pain in the back of the knee.

(Rest in the next issue)