Osteoarthritis: Causes and Treatment Options

What is Osteoarthritis?

Osteoarthritis is a joint disease where, due to various causes, the hyaline articular cartilage suffers often progressive and partly irreversible damage (wear and tear).

This leads to changes in the joint (subchondral bone) and its surroundings (capsule and ligaments, muscles).

J. Lengerke 21:37, 27 May 2009 (CEST), Roe-heberden, CC BY-SA 3.0 DE

Common symptoms, which usually increase gradually, include start-up and weight-bearing pain that worsens over time, restricted movement and stiffness, potentially changes in contour, thickening, and swelling. This can eventually lead to deformities and instability.

We distinguish and define:

Primary Osteoarthritis: The development is idiopathic (meaning without a detectable cause), thus without any additional external factors.

Secondary Osteoarthritis: The result of another disease or cause (e.g., due to arthritis, a trauma with a joint injury).

Polyosteoarthritis: When multiple joints in the body are affected.

Activated Osteoarthritis: A "silent" osteoarthritis can suddenly cause symptoms due to an event (usually trauma, overload). This is typically accompanied by signs of inflammation (swelling, effusion, localized heat, pain at rest). 

How Osteoarthritis Develops

There are various hypotheses regarding the development of degenerative changes in the articular cartilage and osteoarthritis. It appears that osteoarthritis can originate and begin from both sides of the joint: on one hand, starting from the cartilage surface (specifically in cases of trauma, underload, and overload), and on the other hand, simultaneously originating from the bone (shift in the growth zone).

The key primary factors are believed to be:

• Reduced alternation between loading and unloading

• Progressive ossification of the articular cartilage

• Trauma

Reduced Alternation Between Loading and Unloading

This group includes underload as well as age-related degeneration and overload.

As frequently mentioned, underload is perhaps one of the greatest threats to hyaline articular cartilage in our Western society. Because we sit so much, our articular cartilage is no longer properly nourished. In the long run, this lack of supply has negative consequences on the structure and stability of the hyaline cartilage! Due to the lack of pressure changes, the cartilage cells are not sufficiently stimulated to perform synthetic activity. Furthermore, due to the inadequate transport of fluid from the subchondral bone into the cartilage, they also receive too few nutrients. As a result, the cells produce too little matrix, specifically ground substance! Lacking this ground substance, less water can be bound within the cartilage, which reduces the tension of the collagen network. The deformability of the cartilage increases. And due to this greater deformability, the stress on the individual collagen fibrils increases! This makes them susceptible to damage.

Age also plays a role here: As we age, we tend to move even less. And older cells produce less matrix and ground substance, which intensifies this entire issue...

Overload

When a heavy load is suddenly placed on undernourished and untrained cartilage, the limit of resilience is quickly reached and exceeded.

The resulting overload has a traumatizing effect on the collagen network: the first area where damage frequently occurs is the transitional zone (see Blog Articular Cartilage Zone II). Due to damage in this area, the transitional zone can suddenly bind more water (as it is no longer prevented from doing so by the now-defective collagen network). This larger accumulation of water in Zone II also increases the tension on the superficial cartilage zone from below, pushing it toward the joint surface. The cartilage in this area becomes soft and deformable, and it is only a matter of time before damage manifests.

If cartilage material, even the smallest wear particles, gets into the joint fluid (synovia) and thus comes into contact with the capsule, the body views it as foreign material. The capsule responds with inflammation (synovitis).

If pieces of cartilage detach, the holes and tears typical of osteoarthritis are formed. Increasingly, the cartilage can no longer adequately perform its protective function, and the subchondral bone is subjected to increased stress. Consequently, further damage and increasing weight-bearing pain occur in these deeper zones.

All of these factors bring about changes in the cartilage itself. As a result, the collagen network in the articular cartilage can suffer damage and undergo a decline in quality. Any reduced synthetic activity can impair or disrupt matrix production, but changes can also originate from the bone or the vascular and nervous systems. This can also happen after accidents involving compression and heavy impacts with joint involvement: 

Ossification

Another cause of osteoarthritis can stem from changes in the bone. On X-rays, the narrowing of the joint space is recognizable as the first sign. An enlargement of the mineralized cartilage zone is also visible, accompanied by a decrease in the softer cartilage zone.

Due to this reduction in the soft area of the articular cartilage, which is supposed to absorb the pressure load on the underlying bone, the strain during mechanical loading is correspondingly greater. Consequently, the load limit can be reached or exceeded more quickly, which in turn results in damage to the collagen network.

This thickening of the mineralized zone also reduces the osmosis and diffusion processes between the bone and the cartilage zones, which in turn leads to poorer synthetic activity – with the aforementioned consequences and outcomes. 

Trauma

In addition to the mostly slow changes described above that lead to damage, sports injuries or everyday trauma can, of course, also injure and damage the hyaline cartilage. This resulting damage can lead to premature osteoarthritis.

Treatment Options

The extent to which complete healing and regeneration of a damaged cartilage is possible depends on the size and progression of the injury.

In osteopathy and physiotherapy at BodyLab Zurich, the focus lies on pain relief, mobilization, unloading, and training, depending on the current phase and state of the condition. The often restricted joints and tight muscles are treated and stretched using manual techniques, improving the range of motion. Targeted exercises improve muscle building, stability, and load capacity.

Orthopedic insoles are another tool to potentially improve alignment and thereby achieve pain reduction. Crutches can provide acute relief.

Educating and instructing the patient with home exercises and behavioral guidelines is also a vital component of the therapy.

Specific Forms of Osteoarthritis and Their Medical Names

• Spondylarthritis: Facet joint osteoarthritis, osteoarthritis of the spinal joints

• Omarthrose: Shoulder joint (glenohumeral)

• Rhizarthrose: Carpometacarpal joint of the thumb (CMC joint I)

• Bouchard's Osteoarthritis: Proximal interphalangeal joint (PIP joint)

• Heberden's Osteoarthritis: Distal interphalangeal joint (DIP joint)

• Coxarthrose: Hip joint

• Gonarthrose: Knee joint

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Featured Image Credit

J. Lengerke 21:37, 27 May 2009 (CEST), Roe-heberden, CC BY-SA 3.0 DE