Posted on by Roy

What Tom Brady’s and Tiger Wood’s knees have in common. Part II

Somebody as far back as 1900 tried suturing torn anterior cruciate ligaments back together, but that was unsuccessful because of its poor capacity to heal. Next, surgeons tried all sorts of artificial substitutes, silver wire and silk cord among them, but they all stretched out, frayed away, or caused the body to reject them. Somebody even tried using a kangaroo tendon; and now, for older, less athletic people, human cadaver tendon grafts are available. That collagen-dense material is treated to avoid any infectious or immunity issues, but it is not as strong as a tendon borrowed from somewhere in the patient’s own body. The difficulty is that there are few areas where a sufficiently long and thick strip of tendon can be harvested without leaving a problematic donor site. The two current mainstays are a tendon from either the front of the knee or the back.

On the front, the surgeon may take strip of the dense tendon that attaches the kneecap to the tibia. It includes a chunk of bone on each end and is harvested through an incision running down the front of the knee. Then using small stab incisions, an arthroscope, drill bits, and graspers, the surgeon can see inside well enough inside the knee joint to drill holes in femur and tibia and fix the graft in place. (If you are curious, have a look at the procedure on YouTube.) The blocks of bone on each end help the graft heal faster.

The other graft that is frequently used is part of a hamstring tendon from just behind the knee. It is palpable when you are sitting in a chair with your feet pressed firmly on the floor. By trying to pull your foot under the chair, the hamstring muscles contract and tent the skin behind the knee like banjo strings. The incision to harvest a hamstring tendon graft is on the back side of the knee, so the scar is mostly invisible; but the absence of one of these three muscles may result in considerable weakness and put the knee at risk for another ACL injury. So unless the patient is a wrestler or plumber who would object to tenderness just below their kneecap, the bone-tendon-bone graft from the front is usually the chosen donor.

In a newer and incompletely vetted procedure, the surgeon leaves the torn ends of the ACL in place and spans the gap with a plug of bovine-derived collagen mesh. It is injected with the patient’s own blood, which supplies the plug with some of the same growth stimulants that are present in platelet rich plasma.

One potential benefit of this procedure is that it preserves specialized nerve endings residing in the ACL remnants. They are critical for providing position sense. So even though people with torn ACLs might not be all that unstable walking on level ground, they have a sense of their knee giving way most any time because their sensory receptors are not doing what sensory receptors do–receiving mechanical clues and sending them to the brain so that it knows the  levels of stress that the knee is experiencing.

This is potentially a great advantage of using a blood-infused collagen plug–it saves the native sensory receptors. By contrast, for the reconstructions using tendon grafts, the ACL remnants and their imbedded sensory receptors are trimmed out before the graft is placed. Position sense suffers.

Even in the face of a successful ACL repair or replacement, 10-90% of people have some degree of wear-and-tear arthritis 10-20 years later. Despite a successful operation, the joint never glides as precisely as before, so its cartilage surfaces slowly get ground away, sort of like driving a car with the front wheels misaligned–bad for tread wear. Compared to an ACL replacement, it is too soon to know whether an ACL repair will better protect the joint surfaces and offer better position sense with preservation of the sensory receptors.

Rehabilitation after ACL surgery is long and arduous, and the devotion that typically drives elite athletes to succeed is a boon to their recovery. Within a few days after surgery, all the muscles and ligaments in the limb benefit from being moved and mildly stressed to preclude deterioration. A graded strengthening and endurance program extends over at least eight months before the person should try unrestricted activity.

Several tests indicate whether the rehab is complete. The first is known as the timed six-meter (about 20 feet) hop test, first on the recovering leg, then on the sound one. The next is to see how far forward one can get by hopping on one leg and then demonstrating the ability to hop from side to side back and forth over a line on the floor. Try them yourself with your presumably intact ACLs. I did and was pleased that I didn’t fall over.

One last caution for recreational skiers. ACL injuries are more likely with increasing age, icy or new snow conditions, low temperature, and—get this—easy slopes, which is understandable for beginners; but carelessness and higher speeds may account for experienced skiers to catch an edge when they least expect it.

Posted on by Roy

What do Tom Brady’s and Tiger Wood’s knees have in common? Part I

Inside the knee, the anterior and posterior cruciate ligaments are positioned to prevent the tibia (shin bone) from shifting forward and backward, respectively, on the femur (thigh bone). These two interior ligaments along with the collateral ligaments spanning the outside of the joint allow the knee to bend through a 120-150-degree arc of motion while keeping the tibia firmly aligned on the end of the femur. The ACL is the more important of the two and is angled from the back side of the femur to the front edge of the tibia. It keeps the tibia from shifting forward. A rough analogy of its function is to imagine that the femur is a kitchen counter and the tibia is a drawer underneath. The ACL keeps the draw from sliding forward too far. Absent the ACL, the drawer flies out. Chaos ensues.

ACL tears draw greater attention from the people injured, their surgeons, investigators, news media, and the public than all other ligament injuries combined. Out of 900 ligaments in the body, why the ACL? The multiple reasons include the fact that an ACL injury can occur in a high-profile athlete, where it is wincingly reviewable on YouTube and sidelines the star for at least eight months, if not permanently. Soccer standout Megan Rapinoe tore her left ACL in college, had it reconstructed, and returned the next season only to tear it again. Eight years later, the one in her right knee gave way. That is not unusual. Research confirms that nearly a third of people with one ACL tear get another one, in that leg or the opposite, within two years after their first. That should make athletes, team owners, fans, and journalists nervous. Notable athletes who have so far escaped with just one ACL injury include footballer Tom Brady, skier Lindsey Vaughn, golfer Tiger Woods, soccer star Neymar, and basketball great Kawhi Leonard. For pro athletes and their team owners, the ACL is big money. The injury also occurs in high school and college athletes.

When the injury comes to attention, it is a grade III (complete, serious) ligament tear, which destabilizes the tibia on the femur and prevents the sharp turns and sudden stops that are integral to many sports maneuvers. Usually these sudden disruptions do not occur in an entirely normal ligament. It is likely that there has been fraying and degeneration for months, but the dramatic snap of the ACL giving way is the first sign of trouble.

Another reason attention is focused on the ACL is because if investigators and surgeons can solve the ACL problem, then restoration of any other ligament would be easy by comparison. Here’s the reason. Inside the joint the ACL has a paltry blood supply, even moreso than most ligaments. Without much nourishment, its potential for healing is virtually nonexistent. When chronic fraying precedes the fateful snap, the collagen fibers are completely disorganized, which compounds the repair problem.

ACL ruptures often result from sharp twisting and sudden starting and stopping maneuvers. For example, in basketball these injuries are more common in players who like to weave through the defense for layups. Several football players have surprised themselves with this injury stemming from a victory dance. Conversely, direct hits on the knee account for a minor percentage of ACL tears. They used to be common in football, but less so following a rule change that outlawed blocking from behind and below the waist.

ACL injuries are two to nine times more common in young women than men. Several factors seem to contribute. Women’s soccer shoes used to be just pink versions of men’s without any thought whether they fit a woman’s foot or if the cleats were too long for their weight. That has changed. What hasn’t changed is varying levels of estrogen through a woman’s menstrual cycle, peaking at the time near ovulation. The hormone weakens collagen, and there seems to be a correlation between ACL tears and where women are in their menstrual cycle. Also, women tend to jump differently than men and are more likely to land with their knee straighter and the foot pointing directly ahead, both of which stress the ACL. By contrast, ballet dancers, who are perpetually jumping and landing on one foot, are taught to “turnout” with their leg before landing. This aesthetically pleasing foot position seems to protect their ACL, which ballerinas rarely injure. So athletic trainers are helping female soccer players relearn how to jump and to strengthen the muscles that protect the ACL.

Regardless of sex, there is a debate whether knee injuries in soccer are more common on turf or grass. Most studies favor grass. (Several that favor turf were sponsored by turf manufacturers.) Artificial turf, especially when it is dry, tends to grab cleats more than grass does, which I learned when attending a Major League Soccer game at the Mercedes Stadium in Atlanta. No, I wasn’t playing. Rather Atlanta United was facing off against Inter Miami and their new superstar Lionel Messi. He didn’t show up. All we disappointed spectators learned later that his contract allows him to skip games that are played on artificial turf for risk of injury. I suppose in deference to the other players, the groundskeepers turned the sprinklers on the field for five minutes at half time, not to make it grow but to make it more forgiving on the players’ knees.

To be continued.

******************

Posted on by Roy · 1 Comment

What do ligaments look like, anyway?

Ligaments hardly get any respect. By comparison, bones in natural history museums and on X-rays are fascinating. We can also marvel at dissembled ones on otherwise empty dinner plates. Muscles, too, get their due. Since they are just under the skin, we have a sense of their shape, can feel them contact and relax, and note the effects of conditioning and overexertion. Artists have sculpted bulging muscles in bronze and stone figures for thousands of years as expressions of might. Nobody has ever done the same for ligaments.

Without ligaments, however, each of us would be a bag of bones and muscles flopping about without achievement. Consider too that muscle and bone together constitute over half of our body’s weight. Ligaments, by contrast, would hardly tip the scale at all. In spite of their importance, most people (surgeons, meat cutters, and hunters excepted) have never seen a ligament in its natural state, partly because others have fewer opportunities and are less inclined to be poking around, and heating ligaments in the kitchen turns them to mush.

For clarification, ligaments are the tough, fibrous bands that connect bones together. In humans, except for three that run the length of the spine, none are longer than several inches, and many are much shorter. Only occasionally are they thicker than a shoestring, and in the fingers, they are about that wide, whereas at the hip and knee they are much wider and thicker. The gaps that ligaments span between bones are, of course, joints, and ligaments control each joint’s motion.

Ligaments resist stretch and appear microscopically much like tendons; and both, aptly described as connective tissues, cross joints. The elemental difference between the two is that ligaments connect bones together whereas tendons join muscles to bones.

To enhance your appreciation of ligaments, I dissected a fresh chicken. Your ligaments look identical, just larger.

The asterisk identifies the strong ligament on the side of the elbow closest to the trunk–the medial collateral ligament. It resists side-to-side deviation of the elbow and is the cause of many baseball pitchers’ disability. (I will discuss this ailment and its treatment later.)

The asterisks mark the cruciate ligaments, which are located inside the knee. The smaller asterisk identifies the anterior cruciate ligament (ACL), which is prone to tear with twisting injuries. (Details later.)

This vexation also affects dogs. I am not certain about chickens.

Status of book, Ligaments, Appreciating the Bands That Bind Us

February, 2024: Publishing agreement signed with Johns Hopkins University Press

February, 2025: Completed manuscript submitted to JHUP. JHUP sends manuscript out for peer review.

April 4, 2025: Both peer reviews entirely favorable. Several images modified to improve clarity, returned to JHUP April 5, 2025 for the book to “go into production.”

Launch date anticipated for early 2026. Stay tuned for details.