How movements work

What are joints?

Joints are movable connections between solid bones and thus enable all kinds of body movements, such as walking, jumping or grasping. They absorb heavy loads and act as shock absorbers by cushioning sudden, strong forces and thereby protecting the bones from damage. For this cushioning function, joint fluid and articular cartilage are particularly important.

The basic structure is similar in most joints: the ends of the bones are covered by a thin, smoothly polished layer of cartilage that sits closely on the bone and acts as an elastic cushion to absorb compressive loads. This cartilage tissue consists of cartilage cells and a cartilage matrix that in turn contains components such as glucosamine, chondroitin sulfate, hyaluronic acid and collagen. If these components are lacking in sufficient amounts, elasticity suffers.

The entire joint is enclosed by a capsule made of connective tissue. Depending on the joint shape – for example a ball-and-socket joint in the hip or a hinge joint in the elbow – different ranges of motion are possible.

How do joints work?

The movement capabilities of a joint result from its shape and construction: simple, single-axis connections allow movements in only one plane, while more complex joints such as the hip allow rotations and tilting in multiple directions. The force for movement is provided by the skeletal muscles, which run between the bones and span the joints. By contracting or relaxing, they pull the bones together and generate bending or stretching movements.

The tendons attached to the muscles transmit these tensile forces to the bones. Where many tendons pass over joints, they are often embedded in tendon sheaths. The inner layer of these sheaths is coated with a film of joint fluid so that the tendons cause less friction during movement.

At the level of the joint surfaces, smooth cartilage layers ensure that the bone ends do not rub directly against each other, that harder impacts are cushioned, and that pressure is distributed more evenly. In joints such as the knee or the jaw, additional cartilage discs (menisci) complement the fit of the surfaces. Between the joint surfaces there is a gap filled with synovial fluid. This acts both as a lubricant and as a nutrient supplier for the cartilage.

The entire system is enclosed by a joint capsule, whose outer layer consists of firm connective tissue and whose inner, looser layer is rich in blood vessels and nerves. The cells of this inner lining produce the joint fluid. The capsule limits the direction of movement, while muscles, tendons and ligaments further stabilise the joint and thus allow movements and load-bearing.

What are false joints?

False joints are connections between bones that allow little or no mobility. In these cases the bone ends are directly connected by connective or cartilaginous tissue, so typical structures such as a joint gap, joint fluid and a joint capsule are missing. Such fixed connections are found, for example, where the ribs attach to the breastbone or where the pelvis is connected to the sacrum. They serve to link the involved bones stably together.

In medicine these continuous connections are referred to as synarthroses. Some of these connections play a special role during growth, as they serve as a buffer during bone formation. During childhood some of these connections ossify, as is the case with the cranial sutures. In everyday language they are also called rigid or false joints.

Osteoarthritis, arthritis, joint wear – is it all the same?

No, these are not just different names for the same condition. Osteoarthritis refers to a chronic wear process of the articular cartilage, that is, a degenerative disease that is not primarily inflammatory. It often develops gradually with increasing age and is therefore also referred to as joint wear.

By contrast, arthritis is characterised primarily by inflammation of the joint. Although both conditions can cause pain, restricted mobility and discomfort, these similarities do not erase their fundamental differences in origin and course.

Typical causes and symptoms also help to distinguish them: arthritis occurs in flare-ups or persistently with pain, swelling and redness. It can affect several joints at any age and has very different triggers, such as bacterial infections, autoimmune processes like rheumatoid arthritis or metabolic disorders like gout.

In joint wear, the focus is on the slow breakdown of cartilage due to long-term stress. It mainly manifests as pain when starting to move and under load, morning stiffness and often an audible or palpable grinding, especially in heavily stressed joints such as the knee or hip. In addition to age, triggers can include injuries, malalignment or previous joint infections. Because the mechanisms are different, medical approaches to diagnosis and therapy also vary.

What can trigger osteoarthritis?

Osteoarthritis occurs when the articular cartilage is stressed more than it can withstand. This causes damage to the cartilage surface, which heals only slowly and can lead to the loss of cartilage over time. Without the protective cartilage layer, the bones rub directly against each other, which limits mobility and increases pain.

As a reaction, the bone at the joint margins may form additional tissue, leading to visible and palpable deformities. Loosened pieces of cartilage or bone irritate the joint lining and can cause swelling, redness and effusions – a state referred to as activated osteoarthritis.

Various factors can trigger or accelerate this wear. Long-term increased loads due to occupational activities, overweight or intensive sports, as well as persistent misloading in malalignment increase the risk of cartilage damage. Also, sequelae of injuries such as meniscal tears or fractures, as well as inflammatory joint diseases or infections, can permanently damage the cartilage and lead to osteoarthritis. Biological influences such as age, sex and family predisposition also play a role. Lack of joint movement weakens the supply to the cartilage, reducing its resistance to wear.

How to support your joints in everyday life: practical tips

• Pay attention to a diet rich in fresh fruit, vegetables and whole grains to provide your body with important micronutrients. These can neutralise free radicals and positively influence inflammatory processes.
• Also ensure an adequate intake of calcium and vitamin D to maintain bone substance. Incorporate calcium-rich foods into your meals and use sunlight or, if necessary, supplements, especially in months with little sun.
• Regularly include omega-3 sources such as oily fish or flaxseed oil in your diet. These fatty acids have anti-inflammatory effects and can alleviate joint complaints.
• Ensure sufficient protein intake from lean animal sources or legumes so your body has the building blocks for collagen and tissue repair.
• Drink enough fluids, preferably water, as good hydration supports the production of joint fluid and facilitates the frictionless gliding of joint surfaces.
• Watch your body weight, as every extra kilo increases the load on weight-bearing joints. Reduce overweight gradually through lower calorie intake and more activity. If you have been inactive for a long time, medical advice is advisable.
• Choose joint-friendly sports such as swimming or aqua-jogging, as buoyancy in water relieves body weight while strengthening muscles and circulation. When swimming, prefer front crawl or backstroke over breaststroke.
• Use Nordic walking poles when walking to better distribute your body weight. Using poles relieves the joints and at the same time activates many muscle groups, which also helps with weight loss.
• Prefer activities that proceed evenly and without abrupt load changes, such as cycling, cross-country skiing, gentle gymnastics, tai chi or yoga. Such activities promote mobility without causing high impact loads.
• Warm up painful joints before loading them with a heat pack and then move them in circular, gliding movements without strong exertion to minimise pain and support nutrient supply to the joints.
• Protect your joints in daily life through ergonomic measures: pay attention to suitable working heights, avoid remaining in one position for hours and change your posture regularly.
• Lift loads in a back-friendly way by bending your knees and holding objects close to your body. Distribute heavy shopping bags across both arms when possible to avoid unilateral loads.
• Invest in good footwear with a comfortable footbed and cushioning sole as well as a medium-firm mattress that supports the natural shape of the spine. Both reduce unnecessary strain on the feet, legs and back.
• Rest the joint if it is heavily red, swollen or very painful. In such cases, cold applications, anti-inflammatory measures and, if necessary, medication can help until the inflammation subsides.
• Seek medical advice for sudden or persistent joint pain. Be referred to physiotherapy if needed. Early diagnosis and targeted rehabilitation improve the chances of maintaining mobility.

A holistic lifestyle with exercise, a balanced diet and sensible protection is good for your joints. Through small, sustainable changes you can significantly improve your mobility and well-being.