THE KNEE

Background:

• 15% of all sports injuries involve the knee.
• 50% of knee injuries result in a visit to the Dr.'s office. Therefore, when the knee is injured, it is a very likely cause of disability.
• 75% of the surgeries on professional football players involve ligament tears, ACL tears,and the meniscus. There is controversy whether artificial turf fields contribute to an increase in knee injuries.

Statistics

Knee injuries constitute only about 15% of all sports injuries but are 50% of visits to sports doctors, indicating that when they happen, they must be pretty disturbing.

In pro football, knee injuries account for 23% of all injuries, but 75% of surgery is for knee related problems;1/3 of which are due to the medial collateral ligament tear, 1/4 for tears of the ACL, and 1/4 for meniscus injuries

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 injuries

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

Anatomy. 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 who are "bow-legged" 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 meniscus is injured.

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.

Evaluation of knee injuries

Initial exam

identify serious injury needing immediate treatment

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:

1) Was there a distinct injury?

2) What was the specific activity (twisting, deceleration) at the time of injury?

3) Was there an unanticipated move (slip, mislanding)?

4) Was the knee weight bearing at the time of injury?--There is a greater chance of damage to internal structures if so.

5) Was there an external force?..valgus/varus

6) 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)

7) Was there a bad sound (pop, tear, snap)?

8) Is there instability/giving way?

9) What is the degree of disability?

10) Is/was there immediate/delayed swelling? -- Immediate swelling (within 1 hour) indicates blood in the joint. Delayed swelling indicates a synovial reaction.

11) Was there a previous injury?

Ligament injury.

--Joint stabilizers. Knee stability comes from three elements:

1) The geometry of the bones themselves

2) The collateral ligaments/capsule

3) 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, and deceleration.

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 ACL.

Collateral ligament sprain.

Mechanism: direct force; external blow.

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 of function.

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;

healing process ( grade I = 4weeks;

grades II&III = 2-3+months)

Rehabilitation: restore stability, strength and mobility.

Meniscus injury.

-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 because they allow 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 to the person. 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 something else.

Another study done on ACL tears found that when an ACL tear is present, the likelihood that something else is injured is:

60% Medial meniscus.

30% Lateral meniscus.

23% Both.

Anterior cruciate ligament.

--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 more evidence of premature arthritic changes in perople with an ACL repair. Nevertheless, 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:

1) Age of the patient.

2) Activity level.

3) Are other structures injured?

4) 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 risk levels:

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 imprtant.

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 and reconstruction.

Level III: Activities that put little 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

controversy: will ACL reconstruction prevent or delay degenerative changes??

gender differences 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

rehab

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

long-term consequences

meniscal tear

degenerative arthritis

impaired function

gait changes

PCL (posterior cruciate ligament

isolated injury: knee pain 50 %

patellofemoral pain 50%

? arthritis risk

surgical Rx varies

ARTHROSCOPY

1st done 1964 in N.America

ability to see/diagnose/treat

knee>shoulder>other

advantages

limitations

Patellofemoral Syndrome-involves interaction between the knee cap and the bones underneath....can be called a number of things.

chondromalacia-literally the 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 knee pain

-for the most part, patellofemoral syndrome is an overuse injury in a sport where someone does some reptitive motion involving bending and straightening the knee like running, jumping like in track, volleyball, basketball, crew and cycling...sports where you bend and straighten your leg against a resistance which can be your body weight or the resistance of moving a bicycle.

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 your build 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?

-some people are prone to it because of certain anatomical factors

i.e. the knee cap is supposed to be right in the midline and there are some structures that pull it laterally and some that pull it medially, if there's an imbalance, you have potential for a problem

-also, with loss of muscle tone of the active stabilizing structure , the vastus medialis, the knee cap is not going to track correctly and again there is a potential for problems

-anatomical problems that make you prone to this disorder then are:

1) a large Q-angle

2) weakness of the vastus medialis

3) tight lateral ligaments tending to pull the patella to the side

4) 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 injury

Diagnosis: clinical exam

1) talk to them and see what bothers them, find out what kinds of activities they've been doing

2) examine the knee-you will usually find pain with gentle compression of the patella-compressing the patella against the knee causes an irritation to that cartilage or they may have tenderness in the quadriceps tendon or patellar tendon or on the cartilage on either side of the knee cap

-if you move the knee cap from side to side, it's going to hurt if the person has patellofemoral inflammation so you will find pain with various clinical exams

Treatment: Modify things they're doing in their activity that may be leading to it.

-can't change anatomy; orthotics for foot problems

-quadriceps isometric strengthening-straight leg lifts against a resistance to strengthen vastus medialis

-they may need direct treatment of inflammation, may need physical therapy,medication, they can ice knee at end of day

patellar tendinitis

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 by arthroscopy or surgical repair.

bursitis

A bursitis is a traumatic injury usually resulting from a direct blow resulting in inflammation of the bursa.

Diagnosis: One diagnostic consideration is that you want to make sure that it is not an infected bursa requiring treatment for infection rather than inflammation.

Treatment: Standard anti-inflammatory measures.

Rehabilitation of the knee

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 rehab process.

Inflammation of the knee is treated by R.I.C.E. (rest/ice/compression/elevation), anti-inflammatory measures, physical therapy

Goals: You want to maintain flexibility and mobility of the joint, restore strength and function and restore to activity.

If the injury is severe enough, you may need to suggest other activity that is just as satisfying and healthy.

Biomechanical factors: anatomy/training/equipment

All must be evaluated when advising the injured athlete!