Mountain Biking Injuries, Causes and Prevention

As autumn is just around the corner, some of us turn our attention to biking. It is a wonderful way to see and
become literally enveloped in the beautiful fall foliage surrounding us. Mountain biking is a great way to combine
exercise with enjoyment of the outdoors. It became an Olympic event at the summer games in Atlanta in 1996. Its
popularity has been increasing as well as the number of injuries. In this article I will outline the common types of
injuries, their causes and the latest on prevention of these various maladies.

Despite the growing popularity of this sport there have been surprisingly few studies done on injury rates or
mechanisms. The best study I could find was written by Gaulrapp, Weber and Rosemeyer in 2001. It represents a
survey done on 3873 mountain bikers from Germany, Austria, and Switzerland. Injury rates were found to be
comparable to other outdoor sports. The injury risk rate was 0.6%/yr. and 1.1 injuries per 1000 hrs of biking.

Injury types can be divided into two broad categories: traumatic injuries and overuse injuries. In the following
paragraphs we’ll first discuss traumatic injuries then we will discuss overuse injuries.

Traumatic Injuries, Locations and Types

Injuries will be divided into the general location of the injury and the type of injury. The upper extremities
accounted for 45.8% of all injuries. Next are lower extremity injuries coming in at 38.8%. Less common are head
(9.1%) and trunk (6.3%) injuries. Breaking it down by specific injury types brings skin lacerations, wounds and
contusions to the forefront comprising 75.4% of all injuries. 9.9% of all injuries are joint injuries including sprains,
ligament tears and dislocations. 40% of the ligament injuries were acromioclavicular sprains (shoulder
separations). 5.5% of the injuries were fractures. Of these, 24.4% were clavicle fractures, 22.9% finger bones and
9.4% wrist and forearm fractures. Muscle injuries comprised 5.4% and concussions 2.8% of the total injuries.
Other injuries were less common. Serious injuries are reported in the literature including severe facial fractures,
pelvic fractures, intraabdominal injuries and severe brain injuries. Helmets do not adequately protect against facial
fractures. It is interesting to note that there is no significant difference between beginners and experienced riders
in overall injury rates, however, experienced riders have an increased incidence of joint injuries and fractures
compared to beginners.

Mechanisms of Injury and Risk Factors for Traumatic Injuries

Many of the causes of traumatic injuries are preventable. The most common causes cited are slippery surface,
poor judgement, and excessive speed. Poor judgement includes inattentiveness and riding beyond one’s ability.
Excessive speed leads to loss of control or loosing traction while turning. Other causes are unseen rocks, steep
terrain, unseen branches, bumps and small tree stumps. Most of these causes are related to excessive speed
(going too quickly to see the obstacle in time to avoid it) or unfamiliar terrain. Mechanical causes can occur such
as flats but this is a less common cause. During competition there is a four times risk of getting an injury. Injuries
are more severe when the rider is thrown forward over the handlebars than when falling sideways off the bike.

Prevention of Traumatic Injuries

The prevention of these injuries amounts to personal adjustments in the way you ride. A helmet should be a given.
It will protect your head even though you still could get a serious facial injury. Wearing gloves will give some
protection to your hands. Also, wearing a sweatshirt or other piece of long sleeve clothing will give some measure
of protection against scrapes if you fall. It is a good idea to have your bike checked at a shop at least at the
beginning of the season unless you are your own home mechanic. Check your bike before you begin your downhill
descents.  You are less likely to get injured if you check your speed going downhill, but this is common sense. As
you become familiar with certain trails, gradually increase your speed as you are comfortable.

Overuse or Repetitive Trauma Injuries

Low back pain accounts for 37% of the overuse injuries. This low back pain is usually a muscular strain but can
also be an aggravation of an underlying back condition. Knee pain accounts for 30%. The most common ailments
are medial plica syndrome , patellofemoral pain and iliotibial band tendonitis. Wrist pain and/or hand numbness
account for 19%. The wrist pain is usually from the impact on the joints and the numbness is usually caused by
compression of the ulnar nerve at the wrist. Occasionally the numbness can be due to carpal tunnel syndrome as
well. Other overuse injuries can occur including pudendal neuropathy, which in certain instances it is thought to
lead to fertility problems. There is literature both for and against this theory. Scrotal trauma can occur in the form
of micro trauma. Shoulder or arm pain, when they occur, are usually muscle strains.

Mechanisms of Injury for Overuse and Repetitive Trauma Injuries

The three main categories of mechanisms that contribute to these types of injuries are improper bike fit, anatomic
malalignment and training errors. The first thing to do if you have one of the above overuse injuries is to assess
that your bike fit is correct. There is an excellent summary article entitled “How to Fit a Mountain Bike” written by
Dr. Kronisch and published in “The Physician and Sportsmedicine” in March of 1998 that covers this topic in a way
that even a beginner could understand. Small errors in bike fit when combined with long hours of a highly
repetitive motion, a fixed angle of the lower back and arms that are fixed in one position to the handle bars can
lead to overuse injuries. Malalignment problems such as varus or valgus knees, external or internal tibial torsion
and pronation again are amplified during repetitive motions and where these slight deviances to alignment might
not normally bother someone, over a long time or long distance they can. Finally, training errors can lead to
overuse injuries. These include training too hard, inadequate preseason conditioning, sudden increases in
mileage, hill climbing or riding intensity.

Prevention and Treatment of Overuse and Repetitive Injuries

Again for all injuries in these categories, check your bike fit first. Determine if the frame size is correct by straddling
the bike in a standing position. You should have three to six inches between your crotch and the frame. For pedal
adjustment, if you have straps there is probably little you need to do. If you use pedals which firmly attach to your
biking shoes, make sure that they match the rotations of your legs when standing in a natural position. You might
need to rotate them out or in a little bit. Some pedals self adjust and if you have these there is little you would
need to do. Next you should adjust your seat height. Sit on the bike with one foot all the way down and measure
your knee angle. It should be between 25 to 35 degrees. If you have difficulty measuring this angle, ask your bike
shop for help. The next adjustment is to make sure the seat is not too far forward or back. Sit on the bike with the
pedals even. Drop a plumb line to make sure your knee cap is directly over the axle of the pedal. The final
adjustment to the seat is tilt. Use a level to make sure the seat is even or tilted slightly up. This will keep you
seated on the widest part of the seat. The next adjustment is for the upper body position. You should be able to sit
on the bike with your arms relaxed and the elbows slightly bent. Usually the handle bars should be one to two
inches below the top of the seat.
   Low back pain is normally due to lack of proper conditioning. An easy adjustment to do is to raise the handle
bars early in the season and then as you progress, gradually lower them to the proper height. This takes a lot of
the strain off of your back and allows the back muscles to gradually increase in strength. Pre-season conditioning
of the back is very helpful for biking. Back extension excerises and deadlifts are two of the exercises that help. At
the Olympic Training Center they concentrate heavily on many trunk and back exercises (core exercises) because
they are so important for proper sport performance and injury prevention.   
   Knee pain due to medial plica syndrome may respond to elevating the seat and at first avoiding too much
strenuous uphill work. A medial plica is a normal structure in the knee that is located just medial (inside) to the
knee cap. It can become injured or irritated by repetitive activities that involve repeated knee flexion, especially
under stress as in going uphill. This disorder is inflammatory in nature so when you have pain you need to back off
or modify your workout. Good prevention pre-season for this malady is plenty of quadriceps work including half
squats, lunges and the use of an inclined leg press. Knee pain due to pain under the knee cap may be an early
manifestation of arthritis. Again, the same exercise routine as for the plica helps. Antiinflammmatory medications
may help. Check with your doctor before taking these. The same pre-season conditioning applies as for the plica.
IT band tendonitis or iliotibial band tendonitis is irritation of the IT band as it crosses the knee. It will cause lateral
(outside) knee pain. It is caused by the friction of the band rubbing back and forth on the side of the knee.
Lowering the seat sometimes helps. Stretching for the IT band can also help. This condition if it progresses may
require physical therapy or possible cortisone injections in order to cure it. It tends to be stubborn. So if you notice
it coming on modify things immediately. Pre-season stretching of the IT band can help in prevention.
   Wrist pain is due to the vibrations being passed into your wrist. Pre-season pushups can strengthen your wrists
and increase your muscular endurance. Padded gloves can help. Temporarily raising the handle bars will also
help reduce the impact on the wrists. They can be lowered as the season progresses. If you are still experiencing
pain try upgrading your shock absorbers. Wider tires and a lower inflation pressure can soften the impact as well.
   Hand numbness is usually due to compression of the ulnar nerve at guyon’s canal. The little finger side of the
hand goes numb as well as the little finger and part of the ring finger. Guyon’s canal is located just distal to the
wrist in line with the space between the little and ring fingers. This problem can also respond to using padded
gloves and raising the handle bars. It also helps to change grip frequently. An upgrade in shock absorbers can
help. Wider tires and a lower inflation pressure can help. Another cause of hand numbness can be compression of
the median nerve at the wrist known as carpal tunnel syndrome. In this disorder the thumb, index, middle and part
of the ring finger will go numb. This is more due to the constant grip on the handle bars which over a long time can
lead to compression of the median nerve. This will respond to a lighter grip and frequent rest periods. Raising the
handle bars can help.
   Pudendal neuropathy can best be prevented by using a seat with lots of padding and wearing bike shorts that
have the same. Scrotal trauma may be prevented by using proper support. Beefing up the shock absorbers may
help both. Wider tires and a lower inflation pressure can help.
   Shoulder and arm pain are usually due to lack of conditioning. The best single exercise is to do pushups, as
many as you can, as they build up the same muscles used and also increase your muscular endurance.
   Chondroitin sulfate and glucosamine HCL can help with many of these maladies. This is a long term cure taking
up to three months to work. It is thus best to start taking these dietary supplements at least three months in
advance of the season. They also can help to hasten the recovery rate form traumatic injuries. Not all brands are
equally effective. Ask your doctor for advice. Any pain that continues to persist despite all of the above measures
usually warrants a visit to your local doctor. Have fun on the trails, see you there.

Dr. Mark Hopkins is a Board Certified Orthopedic Surgeon specializing in sports medicine. He has worked as a
volunteer physician for the United States Olympic Committee. He is an avid mountain biker and also likes hiking in
the summer.  

Mark Hopkins, M.D.
Board Certified Orthopedic Surgeon
P.O. Box 680518, 1205 Ironhorse Drive
Park City, Utah 84068