01/18/2012 08:11 am ET Updated Dec 06, 2017

Arthritis: When the Knees and Hips Go

Arthritis would seem to be a simple mechanical failure of our bodies. Through wear and tear, the cartilage wears out in certain joints -- primarily the hip, knee, lower back, neck and hands -- leading to stiffness, pain and eventually almost total immobility.  The wear-and-tear explanation appeals to common sense. Evidence for it comes from ancient skeletons, since our ancestors became arthritic, too, and among lower mammals. As pet owners know, old dogs become as stiff and pained in their joints as old human beings.

But the body is never so simple that mechanical explanations are entirely convincing. The more you use your muscles, for example, the stronger they become; they do not wear out. Nor do we see that two people leading the same active life develop bad hips or knees at the same time or to equal severity. In fact, it is disuse that leads to muscle weakness and atrophy. (Interestingly, some people who have joint degeneration, as revealed by X-ray imaging, have no symptoms of OA.)

So what explanation for arthritis takes other factors into account besides wear and tear?

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The most common arthritis affecting hips and knees, the two joints we will focus on here, is known as degenerative arthritis or osteoarthritis (OA). There are many other forms, but in this case the major distinction is with rheumatoid arthritis, which is an autoimmune disease, not connected with wear and tear or aging.  As cartilage wears away, whatever the cause, the bone underlying it degenerates as well. Other parts of the joint -- ligaments, meniscus (a fibrous band covering part of the knee) and muscles -- become altered as well. Inflammation brings a burning pain. Bone spurs can form. Eventually the joint becomes stiff and even small movements become painful and difficult.

OA is the most common form of arthritis worldwide, and the curve is correlated with age. In Western countries the majority of people have OA by the age of 65. About 80 percent of people over who are 75 and older are affected. In the US around 27 million adults currently have OA. This number is expected to go up as life expectancy increases, with the first wave of baby boomers already reaching retirement. Typically, symptoms first begin after the age of 40. The disease can also appear at a younger age, within 10 years after an injury. A 15-year-old teenager who injures her knees playing soccer may have her first symptoms of OA at age 25.

Your joints are remarkable pieces of nature's engineering, moving with almost frictionless ease. In fact, healthy cartilage moves with less friction than a frozen hockey puck over ice. The knee is the largest joint in the body. It connects the femur (thigh bone), tibia (shin bone), fibula (outer shin bone), and patella (kneecap). It is a hinge joint, with a limited range of motion but is very complex compared to a ball and socket. An extensive network of muscles, ligaments, and tendons holds it together, with the added function of stabilizing the join and permitting it to move at the same time -- one reason the knee joint is so prone to injury.

The hip is a ball-and-socket joint located where the femur meets the pelvic cone. A ball-and-socket construction permits the hip joint a large range of motion, second only to the shoulder. The hip joint needs sturdiness to support your weight while standing, walking or running.

The ball-shaped head of the femur is the only moving part of the hip joint. Both the femoral ball and the socket it fits into (the acetabulum) are covered in hyaline cartilage. The femoral ball is attached to the rest of the femur by a thin neck region: this is the part of the hip joint that most often fractures in the elderly.

Now to the elusive question about cause. There are two types of OA: primary (idiopathic) and secondary. Primary OA has no clear cause, although it is related to changes that occur with age, a vague way of pointing to wear and tear. Secondary OA results from a predisposing cause, usually some sort of physical trauma -- knee injuries sustained by professional athletes is a well-publicized example. Causes of secondary OA also include obesity, surgery to the joint structures, defects present at birth, gout, diabetes, alcoholism, the use of corticosteroids and hormone disorders. The good news is that a good many risks can be prevented.

Primary osteoarthritis was once thought to be simple, but it turns out that complex changes to joint cartilage involving inflammation make the cartilage more vulnerable to damage and actually begin the process of cartilage degeneration. Age remains a major risk factor for these changes, but they are not inevitable. About 20 percent of people over the age of 65 aren't affected by OA.

How joints deteriorate

The breakdown of joint cartilage begins long before there are any symptoms. It's thought that in the earliest stages inflammation occurs as cytokines (substances released by the immune system) and other chemicals reach into the joint. As a result, the normal healthy cartilage matrix begins to degrade. Attempts by cartilage cells to repair this damage can cause the cartilage to swell.

Over time, the cartilage softens and loses elasticity. Microscopic flakes and clefts appear on the surface of the cartilage. Joint space narrows as cartilage is lost. Eventually the underlying bone is exposed, and bone rubs against bone inside the joint. The bone becomes increasingly vascularized (filled with blood vessels), thicker, and denser. Cysts may form in the bone, and bone spurs can develop as the bone cells attempt to compensate for lost material. Connective tissue, ligaments, nerves, muscles and even the synovial fluid that lubricates your joints are often damaged as a result of these changes and the stress they bring on.

Symptoms of OA include pain that gets worse as the day goes on, stiffness and decreased motion, swelling in the joint, sounds (like clicking or crunching noises) when moving the affected joint and visible deformity of the joint.

Controlling the risks

The risk factors that you can modify include:

  • Obesity
  • Traumatic injuries
  • Muscle weakness
  • Repetitive mechanical stress
  • Joint infections
  • Diabetes

The risk factors that cannot be modified include advancing age, genetics, female gender and congenital disorders.

Obesity and OA

Being obese greatly increases the risk of developing OA, especially of the knee. Carrying extra weight increases stress on the joints. A force of three to six times total body weight is exerted across your knee when you walk. Being just 10 lbs. overweight increases the force on your knee by 30-60 lbs. with each step. The force exerted across your hip is up to three times your body weight.

Overweight people who lose weight gain relief from OA symptoms, such as stiffness and pain.

The Framingham Osteoarthritis Study found that if obese men lost sufficient weight to be classified as overweight rather than obese, or if overweight men lost enough weight to drop into the normal weight range, the rate of knee OA decreased by over 20 percent. When obese women dropped into the overweight category or when overweight women fell into the normal range, rates of knee OA decreased by even more: 33 percent.

Physical therapy and yoga

OA often creates a vicious circle: a painful joint causes you to restrict your movement, and the lack of movement makes your muscles both weak and tight. If you are experiencing pain and stiffness because of OA, probably the last thing you are thinking about is moving more. But physical therapy (PT) and yoga can be extremely helpful in getting you back to a point where you can perform everyday activities without pain or difficulty.

Physical therapy provides stretching, range-of-motion and strengthening exercises. Strengthening muscles surrounding the arthritic joint helps to stabilize it, increase range of motion and lessen pain. A physical therapist can also show you movement and pain-relief techniques, suggest helpful devices (such as shower stools and long-handled shoehorns), and provide you with a diet plan for weight loss.

Manual therapy, in which therapists employ a variety of hands-on techniques, should be combined with exercise therapy. Combining the two has been shown to dramatically improve results over exercise-based therapy alone.

Yoga can be very beneficial for people with OA because it takes a whole-body approach to joint problems. There is an emphasis on realigning bones and on overall posture, which can relieve stress on the joint and prevent further damage. This can make movement easier and also help to lessen pain.


Eating certain foods and drinking plenty of fluids can help to relieve inflammation, aid flexibility and possibly even prevent further damage.

Inflammation may well play a major role in joint cartilage deterioration, so it makes sense to eat a diet rich in anti-inflammatory nutrients and low in foods that make inflammation worse. These nutrients can fight the inflammation that adds to pain, swelling and further damage to the cartilage.

Foods that are rich in inflammation-fighting free radicals include green tea, berries, fatty fish, extra-virgin olive oil, red grapes and apples, garlic, onions, orange/yellow fruits and vegetables and turmeric and ginger.

Avoid eating foods containing trans fats and also avoid corn oil and peanut oil. They contain arachidonic acid, which may promote inflammation.

Heat and cold

Heating pads and cold packs can ease inflammation, swelling and discomfort. Talk to your healthcare practitioner or physical therapist about the most effective methods of using them.

Topical medications

Topical nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen and naproxen, can be applied to the skin in gels, creams, sprays or patches. They deliver high doses of the medication directly to the joint but keep blood concentrations low, theoretically avoiding adverse side effects (like gastrointestinal problems). Among natural remedies, Capsaicin (derived from pepper plants), applied topically as a cream, seems to be effective in relieving joint pain.


Glucosamine and chondroitin sulfate have been found in some studies to be as effective in relieving pain as acetaminophen and NSAIDs, with significantly fewer adverse effects. The recommended dose is 1,200-1,500 mg daily.


Injections into the affected joint of corticosteroids or hyaluronic acid (for knee osteoarthritis) may work to ease pain for some people with OA, but over the medium and long run, you must consider the major side effects associated with any steroid treatment -- to begin with, you are compromising and sometimes shutting down your body's own production of endocrine hormones.

Looking at the whole picture, we have to concede that aging, wear and tear and injury to the joints still play a big part in why our knees and hips give out.  For prevention, OA can be lumped in with all the other reasons not to become part of America's obesity epidemic. But risks are not the same as causes, and the fact that complex changes occur in cartilage years before any symptoms appear gives an opening for alternative models of the disease.

There is no reason to assume that arthritis is exempt from the body's intelligence, and that disruption in that intelligence somehow plays a part in the early stages.  No firm, precise connection has been made, in part because mainstream medicine still lags in accepting the mind-body connection. But even without a specific connection, your best plan for preventing arthritis is to learn about your body's intelligence, and how the healing system works.

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