What do we prioritize in exercise? Heart rate? Flexibility? Body Composition? We must understand the importance of our joints
and the muscles that surround them. These are the bending/twisting areas in our skeleton that actually creates movement. They are the axes of human levers of bone. Our joints adhere to the same basic design principles of buildings, furniture, and machines, having a strong interrelationship between structure and function. There are many types of joints in our bodies, each having their own specific design according to what they are meant to do. One big difference is that human material/tissues are adaptive. There are several features found in a synovial joint.
Joint Characteristics (Joint Structure and Function, Third Edition)
1. A joint capsule that is formed of fibrous tissue
2. A joint cavity that is enclosed by the capsule
3. A synovial membrane that lines the inner surface of the capsule
4. Synovial fluid that forms a film over the joint surfaces
5. Hyaline cartilage that covers the joint surfaces
Joints can change in response to stress. When we think of creating exercise, we have to understand that each type of tissue in our body has a different response rate and ability. “The keys to progression and adaptation are: 1) The amount of stress introduced 2) the time period over which it is applied 3) the increments and rate of progression 4) the time required for response and recovery.” -Joint Structure and Function, 3ͤ
The issue of joint health is about understanding the anatomy of the individual joint, its capabilities for motion, and its role in the body. For instance, the knee is designed to perform well in extension and flexion and does allow for a small amount of rotation. However, there is bone, ligaments, and tendon that are designed to prevent lateral motion in the knee. The structure of the knee determines its function. An excessive twisting force or force across the knee can be extremely detrimental to the knee. In examination of a hip joint, for example, one can see that there may be more capabilities for motion in many more planes. It is important to note that “Any process that disrupts any one of the parts of a joint will disrupt the total function of the joint” The more complex the joint, the more likely it is to become injured, become afflicted with disease, and experience negative effects of the aging process.
Our joints are covered with a substance called Hyaline cartilage. The purpose of hyaline cartilage is to provide shock absorption as well as a smooth, resilient, low friction surface for movement of one bone on another. The integrity of the hyaline cartilage is vital to joint function. It is capable of bearing one’s weight over a lifetime unless it is abused. With all the advances in medicine, however, we are living much longer than centuries ago, possibly outliving our joints. Cartilage is designed for load distribution, being thinner in areas less tolerant to force. As cartilage is compressed, fluid is released from pores in the outer surface. When the compression ceases, fluid flows back into the cartilage from the synovium and capillaries in the end of the bone. This is called imbibition. The problem is that we live in a society where force can become excessive, such as in sitting position for hours at a time, and the permeability/ fluid flow of the cartilage is decreased. Joints can lose lubrication and become negatively affected by force not being distributed evenly across its surface.
The joint capsule itself has two layers. The outer layer has low vascularization, but is high in joint receptors that sense rate of motion, compression, tension, vibration and PAIN. The inner layer is highly vascularized and poorly innervated. It contains cells that synthesize a component of synovial fluid. It produces collagen and serves as an entry and exit point for nutrients. Keeping this structure in mind, it is the case that pain is often times only felt when the cartilage is considerably worn in an area or even eliminated. At this point, there is no way to get the cartilage to return to an area. There is deep achy pain forever in the joint. The wear of the joint can be described as cracking, popping or clicking as the joint is being used. There are several stages to joint wear, leading eventually to bone-on-bone. We call this process arthritis.
There are two types of arthritis commonly recognized, Rheumatoid and Osteoarthritis. Approximately 1.3 million Americans suffer from rheumatoid arthritis, 27 million from osteoarthritis, and over 300,000 from some sort of juvenile arthritis alone. Rheumatoid is defined as a chronic disease, mainly characterized by inflammation of the lining, or synovium, of the joints, leading to long-term joint damage, chronic pain, loss of function and disability. Osteoarthritis, one of the oldest and most common forms of arthritis, is known as the “wear-and-tear” kind of arthritis. It is a chronic condition characterized by the breakdown of the joint’s cartilage, often called degenerative joint disease, ostoarthrosis, hypertrophic arthritis and degenerative arthritis.
Rheumatoid arthritis Rheumatoid arthritis (RA) is said to progress in three stages. The first stage is the swelling of the synovial lining, causing pain, warmth, stiffness, redness and swelling around the joint. Second is the rapid division and growth of cells, or pannus, which causes the synovium to thicken. In the third stage, the inflamed cells release enzymes that may digest bone and cartilage, often causing the involved joint to lose its shape and alignment, more pain, and loss of movement. RA is a chronic disease that continues indefinitely and may not go away. Frequent flares in disease activity can occur. RA is a systemic disease, which means it can affect other organs in the body and there are many theories about its cause. There is no cure, but various arthritis medications, strategic exercise, and other joint protection techniques can be a way of managing this disease.
Osteoarthritis (OA) also occurs in several stages as well. Improper progression or distribution of force against a joint can cause the cartilage to lose elasticity, synovial fluid distribution to decrease, and cause abnormal wearing patterns across the joint’s surface. Overuse and/or underuse of available joint motion can negatively affect synovial fluid, decreasing the amount of hyaluronan. As the joint dries out, so does its ability to absorb shock. This causes changes to underlying bone, causing it to thicken and form cysts under the cartilage. Bony growths, called spurs or osteophytes, develop near the end of the bone at the affected joint. Bits of bone or cartilage can become detached, floating loosely in the joint space. The joint lining (synovium) can become inflamed due to cartilage breakdown, causing cytokines (inflammation proteins) and enzymes that damage cartilage further. Wear of the joint cartilage changes the shape and makeup of the joint so it doesn’t function smoothly due to the alteration of the contact surfaces. Normal joint forces such as shear, compression, and distraction can become painful during contact, causing swelling, muscle inhibition, and inflammation. In some cases, in order to create surface area across a worn area, bony spurs, called osteophytes can develop near the ends of bones. This further disrupts the relationship between the contact surfaces of the ends of the bones.
Armed with this knowledge, it should be even more apparent that we have a responsibility as fitness professionals to prioritize joint health. It is impossible to even affect heart rate if joint motion is too painful to utilize the skeletal muscle that the heart is responding to! How do we prevent joint wear?
- Change it Up!: an intense study in exercise mechanics can teach the exercise professional how to place different forces across joints to better to alter mechanical wear.
- Altering motor patterns or sequence of events that make up the exercise
- Add force strategically. Can this person deal with their body weight? If not, why do we need to challenge them with external loads?
- Find a Muscle Activation Specialist® that can evaluate your client to detect areas of muscle weakness and help you to create exercises with the goal of muscular balance
- Altering the point in the range where the joint feels the maximal amount of resistance by changing the resistance tool or altering the body’s relationship to the force it is trying to oppose.
- Never violating someone’s active range of motion by moving their joint beyond today’s capabilities
- Understanding that a motion not able to be performed in one joint is likely to be transferred to another joint nearby. Make sure that this joint is capable of moving in that plane.
- Exercise should play with different types of loads, ranges of motion, and activities, but we need to make sure that they do not violate our structure.
- The goal in exercise should be to participate for LIFE, not just prepare for one race or to lose a certain amount of weight. With this perspective, exercise programs take on a whole new purpose.
- Finally, instead of accepting arthritis as a reality, lets make better training decisions and stop it from taking a toll on our bodies!
Norkin & Levangie. Joint Structure and Function, a Comprehensive Analysis. Third Edition. Philadelphia: F.A. Davis Company. 2001