The elbow: A flexible joint with a 'funny bone'

By: BRADLEY J. FIKES - Staff Writer | Saturday, February 3, 2007 7:07 PM PST ∞

The elbow is one of the most flexible joints in the body. It allows the upper arm to be extended or contracted, and also moved from side to side to a limited degree. Whether the job is cracking a walnut, typing on a keyboard or performing cardiac surgery, the elbow positions the wrist precisely so the hand can manipulate objects with microscopic degrees of accuracy.

The elbow has a close cousin in the knee. Both joints connect limb segments with two bones to segments with one bone. In the knee, the femur, or thighbone, meets with the tibia and fibula in the lower leg. In the elbow, the humerus (or "funny bone") of the upper arm meets with the radius and ulna in the lower arm. However, the elbow allows much greater sideways motion than does the knee.

Elbows, then, are the junction of three bones, the humerus, radius and ulna. They're connected with ligaments, which connect bones with bones, and tendons, which connect muscles to bones. If you flex your elbow a lot with weight-lifting, you'll develop bulging biceps, the biggest muscle that flexes the elbow. The triceps does the opposite; it extends the elbow.

Elbows do not have an equivalent of the protective patella, or kneecap. This becomes painfully evident if you bang your elbow and get a jolt of temporary agony. You've hit the "funny bone," which is actually the ulnar nerve.

Because there is no "elbowcap," the ulnar nerve is vulnerable where it crosses the elbow. This nerve runs from the shoulder to the hand. Throughout most of its path, the ulnar nerve is well-protected, lying deep inside the arm. But at the elbow, it runs near the surface for a short distance.

The joint is cushioned by cartilage that lines the bone endings, so they glide past each other smoothly. Another cushioning mechanism is the bursa, a small, fluid-filled sac at the very tip of the elbow. If you constantly put pressure on the elbow, such as from leaning on it at your desk, or the elbow gets hit, the bursa may become inflamed, and even bleed. This inflammation is called bursitis.

Elbow tendons get inflamed fairly often when heavy stress is put on the joint, such as when playing tennis. Doctors call this "lateral epicondylitis" or in layman's terms, "tennis elbow."

Treatment for these common inflammations can be as simple as ice and rest, or it may require a trip to the doctor for a steroid injection (to reduce the inflammation) or even surgery. If you get such an injury that causes persistent pain, see a doctor, preferably one trained in sports medicine.

Extensive damage to the elbow, whether from overuse or diseases such as arthritis, may become so severe that the elbow joint must be replaced. When the cartilage is worn down, bone rubs against bone, producing great pain.

A replacement elbow is made of metal and plastic that rub against each other more smoothly than does bone. The most common type is a hinge, one end anchored in the humerus, the other in the ulna.

Like a hip joint replacement, a replacement elbow is not as sturdy as the real thing. The hinge may loosen over time and need further surgery. For this reason, elbow replacement surgery is usually a last resort. It's often done in older people, who are likely to be less active.

A less drastic alternative is surgery to encourage the regrowth of cartilage. This procedure was performed in October on Mark Lowe, a pitcher with the Seattle Mariners. In late January, Lowe said his elbow was healing, and he planned to begin practicing soon.

-- Contact staff writer Bradley J. Fikes at (760) 739-6641 or bfikes@nctimes.com.

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