Knee Injuries in Runners

KNEE INJURIES IN RUNNERS

INTRODUCTION

Knee injuries in runners are typically caused by biomechanical problems above or below the knee.  Most common knee injuries are have been broken down into the areas of pain:

ANTERIOR KNEE PAIN

Patellofemoral pain syndrome (PFPS), quadriceps tendonitis/opathy, patellar tendonitis/opathy, Hoffa’s fat pad syndrome, osteoarthritis/chondromalacia patella, bursitis.

MEDIAL KNEE PAIN

PFPS, medial collateral ligament sprain, medial meniscus tear, osteoarthritis

LATERAL KNEE PAIN

PFPS, Iliotibial band syndrome (ITBS), popliteus muscle strain, lateral collateral ligament sprain, lateral meniscus tear, osteoarthritis

POSTERIOR KNEE PAIN

Baker’s cyst, hamstring tendonitis/opathy, popliteus muscle strain

Though this is not an exhaustive list of knee problems from running, it provides an ideal of the different structures that can potentially be injured.  This article will review the two most prevalent knee injuries experienced by runners; PATELLOFEMORAL PAIN SYNDROME (PFPS) AND ILIOTIBIAL BAND SYNDROME (ITBS)

PATELLOFEMORAL PAIN SYNDROME (PFPS)

PFPS is one of the most common problems experienced by runner (keep in mind, SYNDROME is merely a collection of signs and symptoms). Pain generators for PFPS include infrapatellar fat pad (between tibia and patellar tendon), bursa, tendon and the patella itself (bone).  Females typically experience PFPS more often than males.  Biomechanical issues such as wider hips and increased internal rotation of the femurs causing poor tracking of the patella that irritates structures that hold the patella in place (patellar tendon, joint capsule etc). 

PRESENTATION

The classic onset of PFPS is:

-insidious onset of progressively worsening anterior knee pain, worse with increased running distance or time

-pain is typically described as diffuse and achy, worse in the morning, and may be sharp with activity

-aggravated with prolonged sitting with knees in flexion (such as on an airplane, or in a movie theater). 

-pain may be felt along or within the patellar tendon if there is tendinopathy

TREATMENT

Initial treatment for PFPS should include at symptom relief.  This should include reducing or stopping running or any other insulting activities.  If there is swelling, ice may help to reduce discomfort

During the rehabilitation phase, isometric exercise may be beneficial if the patient is still suffering from pain.  This might include simple contraction of quads while the knee is straight or slightly bent.  Therapy for tight structures such as muscles and tendons have been found to be beneficial. 

For later phases of rehabilitation, functional closed kinetic chain exercises have been found to be very effective in reducing incidence and reoccurrence of PFPS.  Exercises focusing on hip/gluteal strengthening should be included.  Squatting, lunges and single leg exercises focusing on maintaining knee and hip stability are encouraged.

ILIOTIBIAL BAND SYNDROME (ITBS)

ITBS and PFPS are considered separate diagnoses, though they have common signs and syptoms.  The ITB is a dense fascial band that runs down the lateral aspect of the thigh.  It has extensive connections to the gluteal muscles, tensor fascia latae (anteriolateral muscle of the hip) and to a number of structures around the lateral aspect of the knee. Originally, it was thought that friction over the lateral femoral condyle was the cause of irritation to the ITB (just above the lateral aspect of the knee).  Current research has shown that it may not be friction (the ITB does not actually slide) but compression of a fat pad or bursa in the area of pain (typically lateral aspect of the knee). 

PRESENTATION

The classic presentation of ITBS is:

-pain felt in the lateral hip, thigh and more commonly, the lateral aspect of the knee

-slow onset of achy/burning pain that gets worse with increased running time or distance

-pain is typically felt when knee is flexed at 20-30 degrees and worse running downhill

-paradoxically, pain typically (but not always) decreases with faster running

TREATMENT

Initial treatment for ITBS should aim at symptom relief.  Though there is little research on the efficacy of stretching the ITB, anecdotally there are many records of moderate relief of symptoms from stretching and foam rolling the ITB.  Caution must be exercised when rolling ITB, particularly over the lateral knee as structures may become more inflamed and irritated.  Just as PFPS, once pain is reduced, rehabilitation should focus on hip strengthening exercises.  These exercises should emphasize close kinetic chain exercises such as squats, lunges and single leg exercises.

COMMON QUESTIONS

WHAT IS THE DIFFERENCE BETWEEN PFPS AND CHONDROMALACIA PATELLA?

There is no difference between PFPS and chondromalacia patella though CMP can be considered a cause or sign of PFPS.  Chondromalacia patella was believed to be a major cause of anterior knee pain (feeling of pain under the knee cap).  CHONDROMALACIA PATELLA is a roughening of the cartilage on the underside of the knee cap.  HOWEVER, IT IS KNOWN THAT CARTILAGE IS NOT INNERVATED BY NERVES AND THUS IS NOT LIKELY A SOURCE OF PAIN.  Current theories of causes of pain include subchondral bone injury (like a bone bruise beneath the cartilage) or damage to nerve endings that innervate the joint itself (such as the joint capsule)

CAN THE VASTUS MEDIALIS OBLIQUUS (VMO OR MOST MEDIAL QUADRUCEP MUSCLE) BE PREFERENTIALLY RECRUITED?

Recent research has shown that preferentially recruiting VMO does not occur.  Thus, exercises aimed at activating the VMO should not be given.  Instead, the aim should be toward functional exercises involving the whole quadriceps muscle.  Exercises including closed chain squatting, lunges, and single leg exercises should be recommended.  Exercises that should be avoided include squeezing a ball between the knees while squatting, using bands that place lateral stress on the knee while squatting and hip adduction and leg extension exercises using machines. 

TAKE HOME POINTS

THERE ARE MANY SOURCES OF KNEE PAIN FROM RUNNING. THE TWO MOST COMMON CAUSES OF KNEE PAIN ARE PATELLOFEMORAL PAIN SYNDROME (PFPS) AND ILIOTIBIAL BAND SYNDROME (ITBS)

PFPS IS TYPICALLY ANTERIOR KNEE PAIN FROM THE BURSA, TENDON, FAT PAD OR BONE.  IT DIFFERS FROM ITBS AS ITBS IS A SOURCE OF LATERAL KNEE/THIGH PAIN. 

PRESENTATION OF PFPS INCLUDES WORSENING KNEE PAIN WITH INCREASED RUNNING, AND PAIN WHILE SITITNG WITH THE KNEES FLEXED

PRESENTATION OF ITBS INCLUDES WORSENING LATERAL KNEE/THIGH PAIN WHILE RUNNING UP HILL. 

BOTH PFPS AND ITBS SHOULD BE TREATED WITH REHABILITATION.  ONCE PAIN SUBSIDES, REHABILITATION SHOULD FOCUS ON CLOSED KINETIC CHAIN EXERCISES WHILE MAINTAINING HIP AND KNEE STABILITY

THE VASTUS MEDIALIS (OBLIQUUS) CANNOT BE PREFERENTIALLY RECRUITED. THUS, TRAINING SHOULD FOCUS ON QUADRICEPS AND HIP/GLUTE ACTIVATION