Perspective on knee injuries
Evaluation of injury
Knee ligament injury
of knee sprain
of chronic knee disability
of knee braces
Anterior Cruciate Ligament
- Mechanism of injury
- Treatment options
- Surgical considerations
- Gender differences
9. Other conditions
band friction syndrome
Rehabilitation after Injury
15% of all sports injuries involve the knee.
50% of knee injuries result in a visit to
the doctor's office. Therefore, when the knee is injured,
it is a very likely cause of disability.
75% of the surgeries done on professional
football players involve ligament tears, ACL tears,and the
meniscus. There is controversy whether astro turf fields
contribute to an increase in knee injuries.
Knee injuries constitute only about 15% of all sports injuries
but are 50% of visits to sports doctors, indicating that when
they happen, they are usually significant.
In a 3 year study of high school athletes (24,000 males, 15,000 females):
- basketball had the greatest number
of participants and the highest injury rate
- when all sports were combined, ankle
injuries were the most common, followed by leg
injuries, then knee injuries for males
- for females, ankle injuries were again
the most common, followed by knee injuries, then leg
Knee injuries are the most common cause
of the athlete being lost for the season.
- season ending injuries: 50% due to
sprains or dislocations
- 30% were due to meniscus tears
- 5% due to fractures and the
- remaining 15% to other causes
Knee injuries are common in all sports:
- 42% basketball (42% of injuries
among basketball players)
- 29% ...dancers
- 43% ...football
- 31% ...gymnasts
- 38% ...runners
- 67% ...skiers
- 46% ...soccer
- 24% ...tennis
The knee is a hinge joint but a little medial rotation of
the femur occurs with
full extension. The knee is very stable, its stability comes from the geometry
of the bones themselves, the ligaments and the muscles.
Bones: More specifically the knee
is the interaction between the femur and the tibia. Note also
that the patella articulates with the femur. Q-angle describes
the alignment between the tibia and the femur--it is an important
factor in overuse injuries of the knee. People who are "knock-kneed" have
a large Q-angle and people with a straight leg alignment have
a small Q - angle. The patella facilitates quadriceps function.
It is also a factor in overuse injuries of the knee.
Muscle groups: The quadriceps are
the knee extensors. The quadriceps muscle group consists of four
muscles: vastus medialis, vastus lateralis, vastus intermedius
and rectus femoris. The quadriceps muscle group inserts across
the top of the patella and originates at the anterior, inferior
iliac spine. When these muscles contract, they pull laterally.
The vastus medialis counterbalances this by pulling medially.
In a lot of knee injuries, the vastus medialis loses strength
relatively quickly. Therefore, it is important to restore the
strength to this muscle during rehab or else the knee cap won't
move /track in proper alignment.
The hamstrings are responsible
for knee flexion. The hamstring tendons (together as the pes
anserine group) also give medial support to the knee.
Medial stabilizers: The medial stabiliers
of the knee are the medial collateral ligament (MCL),
medial capsular ligament, medial retinaculum and the pes anserine.
The MCL attaches to the medial meniscus. Therefore, a co-existing
injury may be present; if the medial collateral ligament is injured,
the medial meniscus may be injured as well.
Posterior elements: The popliteal
space is the well protected, diamond shaped space behind the
knee through which nerves (the sciatic nerve in particular) and
blood vessels (popliteal artery and vein) run. A dislocation
of the knee is a serious injury because it can cause damage to
the nerves and bloodvessels in the popliteal space.
Lateral stabilizers: The lateral stabilizers
of the knee are the lateral collateral ligament (LCL),
the capsule, and the illiotibial band (which contributes to overuse
injuries in the knee). Unlike the MCL, the LCL is not attached
to the lateral meniscus. Therefore, the lateral meniscus is injured
only about half as much as the medial. Injuries to medial structures
are more common than injuries to lateral structures since you
are more likely to be hit from the side, a valgus force.
Internal structures: The menisci of
the knee are thin, halfmoon-shaped cartilagenous structures that
provide cushioning to the knee. There is both a lateral and a
medial meniscus in the knee. The medial meniscus is thin and
attaches to the MCL. The lateral meniscus is thicker and does
not attach to the LCL. The anterior cruciate ligament (ACL)
attaches from the back of the femur to the front of the tibia
and prevents the tibia from moving anterior relative to the femur.
The posterior cruciate ligament (PCL) attaches from the
front of the femur to the back of the tibia and prevents the
tibia from moving posterior relative to the femur.
- identify serious injury needing immediate
- record details of injury
- gross stability tests
- splint/first aid
- transport to care
History of injury: When taking a history
it is important to get as much detail about the injury as possible.
The more detail you can get, the better idea you will have about
what is injured. Most importantly, if you know the type of force
involved and the position of the lower leg, you can get an idea
of which structures may be injured. When taking a history, it
is important to determine:
- Was there a distinct injury?
- What was the specific activity (twisting,
deceleration) at the time of injury?
- Was there an unanticipated move (slip,
- Was the knee weight bearing at the time
of injury?--There is a greater chance of damage to internal
structures if so.
- Was there an external force?..valgus/varus
- Is/was there pain? Pain is usually proportional
to the amount of damage (except in a Grade III injury in
which nerve fibers may be disrupted)
- Was there a bad sound (pop, tear, snap)?
- Is there instability/giving way?
- What is the degree of disability?
- Is/was there immediate/delayed swelling?
-- Immediate swelling (within 1 hour) indicates blood in
the joint. Delayed swelling indicates a synovial reaction.
- Was there a previous injury?
Knee stability comes from three elements:
- The geometry of the bones themselves
- The collateral ligaments/capsule
- The muscle groups.
If any of these are deficient due to injury
or due to inadequate rehabilitation, a person will tend
to have ongoing problems/disability.
Mechanism of injury:
The structures injured usually depend on
the type of force involved and the position of the lower leg
at the time of injury (was it in rotation?). Common forces
involved in knee injuries are valgus (from the side), twisting,
The position that the knee is in at the
time of the injury is crucial in determining which structures
have been injured.
A valgus force (force from the side)
injures the medial aspects of the knee -medial meniscus, medial
collateral ligament, ACL(aka the "terrible triad")
A varus force (from the inside)
injures the lateral structures
More often the knee is injured with a valgus
force with external rotation of lower leg.
(A valgus force can refer to an external
force as in football, or the weight of an athlete who
is moving in any sort of running sport, i.e. a soccer
player who plants foot and goes to change direction)
A deceleration force with the leg
in a neutral position stresses the ACL.
A valgus force + external rotation is
high risk for injury to medial structures and the ACL. The "terrible
triad injury" is an injury to the MCL, medial meniscus, and
Collateral Ligament Sprain:
Mechanism: direct force; external
There are three grades of collateral ligament sprains which vary with the degree
of the symptoms:
- Grade I: some fibers torn but the
stability of the ligaments are intact.
Symptoms: pain, mild disability, tenderness over the medial structures, little
or no swelling, but the joint is stable.
- Grade II: enough fibers are torn
to cause instability.
Symptoms: more pain, more disability, local tenderness, swelling common,
moderate loss of function.
- Grade III: complete disruption
of the ligaments.
Symptoms: can be painless or painful, a lot of instability/disability, loss
Diagnosis: clinical diagnosis (doctor's
physical exam of the knee).
Treatment: non-surgical; surgeries
done mostly in conjunction with the repair of other structures
in the knee:
- grade I = 4weeks
- grades II&III = 2-3+months
Rehabilitation: restore stability,
strength and mobility.
Anatomy and function: The menisci
are made of cartilage and collagen and
have a limited blood supply (and therefore
limited healing capability). The menisci
not only act as a cushion between the
femur and the tibia but they also act
as stabilizers for the bones and allow
for proper movement/tracking between
the femur and the tibia. The menisci
also have a nutritional function by allowing
synovial fluid to flow up and around
the knee joint.
Mechanism of injury: External force
or twisting movement causing a tear.
Symptoms: Effusion/swelling; locking;
joint line tenderness over the MCL (since the medial meniscus
is attached to it); quadriceps atrophy (particularly of the vastus
medialis); sensation of "giving way"; abnormal sound (clicking).
Diagnosis: Clinical exam; MRI for
confirmation. You can also use arthroscopy if necessary (arthroscopy
has a high sensitivity, specificity and predictive value).
Treatment: Treatment depends on the
activity level of the person and how much of a problem the injury
is causing. Some people can function fine without a meniscus
repair. Repair vs. removal...
Likelihood of coexisting injury: A
study done on acute knee injuries requiring surgery found that
the likely causes were:
- 80% Medial meniscus injury
- 70% ACL injury
- 30% Lateral meniscus injury
If you notice, these numbers add up to 180%
therefore, when one structure is injured, it is usually in
conjunction with damage to another structure.
Another study done on ACL tears found that
when an ACL tear is present, the likelihood of co-existing injury:
- 60% Medial meniscus
- 30% Lateral meniscus
- 23% Both
Anatomy and function: The ACL lies inside the knee joint. It attaches from
the back of the femur to the front of the tibia and prevents the tibia from
moving anterior to the femur. The ACL has poor blood supply and therefore,
poor healing capabilities.
Mechanism of injury: Valgus, twisting,
or deceleration force.
History. The most common history of an ACL
injury is a bad sound (snap/pop) with immediate disability and
immediate swelling (thus indicating blood in the joint).
Diagnosis: Clinical exam/MRI
Treatment options: ACL tears can be
surgically repaired (reconstructed). However, surgical repairs
may have long term effects on the joint--there is some evidence
of premature arthritic changes in people with an ACL repair.
However, there are also concerns about treating ACL tears nonsurgically
since 20% of those with an unrepaired ACL suffer from a meniscus
injury within 5 years.
Surgical considerations: If surgical
reconstruction is the mode of treatment being sought, it is important
to wait 4-6 weeks before doing the procedure so that the patient
can get full range of motion back and therefore speed recovery.
Factors that must be taken into consideration when considering
surgical ACL repair:
- Age of the patient.
- Activity level
- Are other structures injured?
- What is the person's sport specific degree
of involvement? Is using a brace a possibility?
This usually depends on the risk level of
the sport in which the person participates. There are three different
Level I : Sports that involve jumping,
pivoting and cutting, deceleration(basketball, football, soccer)
and that put the ACL and meniscus under a lot of stress. For
people involved in these activities, ACL repair is important.
Level II: Sports that involve lateral
motion (baseball, racquet sports, skiing). For people involved
in these activities there is more of an option between rehabilitation
Level III: Activities that put less
stress on the knee (jogging and swimming). For people involved
in these activities, rehabilitation is an option.
Surgery likely if:
High risk sport/Competitive athlete/Recurrent instability/Meniscus injury
Will ACL reconstruction prevent or delay degenerative changes??
In ACL injury: college female athletes have 2-4 times the
risk of ACL injury in soccer, volleyball, basketball. Theories
include to role of:
- estrogen receptors
- femoral notch geometry
- muscle firing patterns
Surgical methods and considerations:
- graft selection
- graft placement
- graft fixation
- return to sports
- graft strength over time
- intercondylar notch
Predictors of need for surgery:
- hours per year of level I or II sports
- degree of displacement tibia: femur
- frequency of instability
- meniscal tear
- degenerative arthritis
- impaired function
- gait changes
PCL (posterior cruciate ligament)
- isolated injury: knee pain 50 %; patellofemoral
- ? arthritis risk
- surgical Rx varies
- 1st done 1964 in N.America
- ability to see/diagnose/treat
Patellofemoral Syndrome involves
interaction between the knee cap and
the bones underneath. Synonyms: chondromalacia,
anterior knee pain.
softening of cartilage but this may refer to a condition in which
the cartilage is just inflammed so it's not really soft, just
irritated. Also known as patellar subluxation or anterior
For the most part, patellofemoral syndrome
is an overuse injury in a sport involving repetitive motion,
especially bending and straightening the knee as in running,
jumping, volleyball, basketball, crew, and cycling or sports
involving bending and straightening the knee against resistance
(body weight, bicycle, etc.).
Overuse injuries can be defined as microtrauma due to repetition, just
the repeated stress of exercise causing small areas of tissue inflammation.
When evaluating these problems, several contributing factors need attention:
- Anatomy: is there anything about
the athlete's physical make-up that is contributing to the
problem, such as high arches, flat feet, unequal leg length?
- Equipment: are the shoes you are
wearing worn out, or not the right ones for your feet?
- Training: are you running too many
miles, too many hills, too much time on hard surfaces?
Anatomical problems increasing susceptibility
to this disorder:
- A large Q-angle
- Weakness of the vastus medialis
- Tight lateral ligaments tending to pull
the patella to the side
- Shallow anatomy of the groove on the femur
(if the fit is not good, the patella can easily displace
to one side or another
Patellofemoral syndrome is an overuse
Diagnosis: Cinical exam
- Talk to the athletes, see what bothers
them, find out what kinds of activities they've been doing
- Examine the kneeyou will usually
find pain with gentle compression of the patella; compressing
the patella against the femur causes discomfort. Pain with
knee straightening against resistance.
Treatment: Modify aspects of exercise
that may be contributing.
- Can't change anatomy; orthotics for foot
- Quadriceps isometric strengthening-straight
leg lifts against a resistance to strengthen vastus medialis
- May benefit from direct treatment of inflammation,
such as physical therapy, medication, use of ice packs
Patellar subluxation is a partial dislocation with the patella somewhat displaced
to the side.
The most extreme form is patellar dislocation
to the side (no longer an overuse injury). It is a sudden severe
disabling injury where all medial structures are torn. It may
be caused by a strong quadriceps contraction where lateral forces
overcome the medial restraints which are the medial igaments
and the vastus medialis.
Usually with a dislocation there is a coexisting
internal injury. Often there force is strong enough to pull
a piece of cartilage off on the backside of the patella or to
pull off or chip a bone. This large force can cause a loose body
floating around in the joint that needs to be treated usually
A bursitis is a traumatic injury usually resulting from a
direct blow resulting in inflammation of the bursa.
Diagnosis: One important diagnostic consideration
is to distinguish injury and inflammation from an infected bursa
requiring specific treatment.
Treatment: Standard anti-inflammatory measures.
Main Rule: Damaged tissue needs
time to heal. Things that take time to
develop or injuries caused by a large
force do not go away quickly. Acute pain
and swelling need to subside before the
person can partricipate in an active
Inflammation of the knee is treated by R.I.C.E.
(rest/ice/compression/elevation), anti-inflammatory measures,
Goals: To maintain flexibility and
mobility of the joint, restore strength and function and allow
return to activity.
If the injury is severe enough, changes in
exercise habits may be necessary.
Biomechanical factors to be evaluated:
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- anatomical factors
- training factors
- equipment factors
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purposes only and is not intended to be a substitute for medical advice.
Always contact your doctor if you feel you need medical advice or treatment.