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Anatomy and Examination/Imaging

The knee is one of the most often injured joints in the body.  It is subjected to tremendous stresses as we go about our daily lives moving around, carrying heavy loads, and playing sports.  The knee is basically a complex hinge.  The kneecap helps to make the thigh muscles work more efficiently.  The ligaments of the knee stabilize the tibia (shin bone) and the femur (thigh bone) as they move against each other.  The soft covering over the ends of the bone (articular cartilage) and the menisci cushion the surfaces of the knee and allow for smooth motion.

Injury to the knee can include fractures (broken bones) or tears of the soft tissues (ligaments and cartilage).  Typically, the knee becomes very painful and/or swollen after a significant injury.  The swelling may occur immediately or after a few hours or even days.  Other painful conditions of the knee exist that are not caused by an acute injury.  These problems are often due to muscle imbalance, malalignment of the kneecap, or damage to the articular cartilage covering the end of the bone.  Evaluation of the knee involves getting a history of the problem, a physical exam, x-rays, and possibly an MRI to look at the soft tissues better or a CT scan to look at the bones better.  Most knee problems can be treated non-surgically while others require surgery to allow a return of function.

Meniscus Tears

Meniscal tears are very common and can cause a significant amount of pain and dysfunction. The menisci are C-shaped structures made of collagen.  They cushion the bones and are subject to severe stresses as people twist there knees and move into deep flexion.  The torn tissue can then irritate the inside of the knee.  Menisci naturally degenerate over time making these tears more likely as one gets older.  The result is a painful knee that often has tenderness over the meniscus on the inside or outside of the knee, swelling, catching sensations or locking, and possibly even giving way of the knee.  The tissue has a poor blood supply and has a difficult time healing itself.  Non-surgical treatments include ant-inflammatory medications, rest, and ice.  Arthroscopic surgery is often indicated when non-surgical treatments fail or when a repair may be possible to save the tissue.  Depending upon the quality of the tissue, the pattern of the tear, and the potential to heal, the meniscus can either be repaired or the torn portion can be resected (menisectomy) in order to prevent symptoms from recurring.  The recovery after a menisectomy is usually 6-8 weeks.  Most patients do not need to use crutches and can return to work within a few days.  Meniscus repairs require a longer recovery in order to protect the repair. 

Ligament Injuries

Ligament injuries of the knee can involve one or more of the four main stabilizing ligaments. Ligaments are essentially ropes that hold two bones together allowing for motion at a joint but  limiting that motion so that the bones do not separate (dislocate) from each other.  They are also made of collagen and can tear.  Some ligaments have a capacity to heal spontaneously while others do not.

Anterior cruciate ligament (ACL) ligament injury is very common.  The ACL is the main stabilizer of the knee as we perform cutting or side-to-side activities and actions that require stopping and starting.  Most injuries occur after plant the foot or land on the leg after jumping and twisting the knee.  Other times a direct blow to the knee can tear the ligament.  ACL injuries can occur in isolation or other structures can also be involved including other ligaments, the menisci, the bone, and the articular cartilage.  ACL ligament tears do not heal by themselves.  Once torn, the ligament will remain loose but the patient may or may not have problems with the knee after the initial swelling and pain have resolved. The main symptom after an ACL tear is looseness or giving way of the knee.  Patients that are younger and more active are more likely to have trouble with there knees after an ACL tear and are at a high risk of injuring other structures in their knees because of the potential for the knee to give way after an ACL tear.  Non-surgical treatment includes controlling the swelling and pain followed by exercises to return motion and strength the knee.  Surgical treatment involves removing the torn ACL remnants and grafting a new ligament in its place.  The new ligament is made either form tissue harvested from the patient (autograft) or from process tissue from an organ donor (allograft).  There are several different types of autografts and allografts used that have their specific benefits and risks. We are proficient with the use of all graft types and individualize graft selection for each patient after a thorough discussion.  Complete recovery from the surgery usually takes 4-6 months and requires some bracing and rehabilitation.  Rehabilitation is arguably the most important part of the process.  In order for the knee to return to good function, the patient must get the knee to move and regain strength of the leg muscles.  Most patients work with a therapist although the exact process of rehabilitation is also individualized.

Revision ACL reconstruction is challenging but can provide significant relief for patients with knee instability after a previous reconstruction.  Revision surgery can involve removal of hardware, bone grafting the previously created tunnels for ligament reconstruction, and finally reconstruction of the ACL.  Many times, the revision can be performed with one procedure. Occasionally, a revision must be performed in two stages in order achieve a good result.

Other ligaments around the knee including the posterior cruciate (PCL), medial collateral (MCL), and lateral collateral ligaments (LCL) can be injured.  Often, theses can be treated non-surgically.   If one or more of these ligaments is torn in conjunction with other structures, surgery can sometimes be necessary.  The PCL usually requires grafting like the ACL unless an avulsion has occurred.  The MCL and LCL can often be repaired although in specific cases grafting is needed.

A ligament avulsion happens when the ligament tissue has withstood the injury but the bony attachment has failed so the ligament tears loose from one of its ends with some bone still on it.  These injuries are more common in younger patients but can happen in all age groups.  If the bony attachment has not pulled away completely, it will often heal with rest and bracing to protect it.  If the bone has pulled away then surgery may be indicated to repair the bony attachment and restore the ligament function without the need for grafting.

Anterior Knee Pain

Many people develop pain in the front of their knee.  The pain is usually felt under the kneecap but can be more towards the inner knee, outer knee, or even the back of the knee. Usually, the pain is achy or burning.  The knee can also feel like it wants to give way.  Pain often occurs when going up or down stairs and when seated with the knee bent for a long time. There are a variety of reasons that people get pain from the patellofemoral (kneecap) joint.  The main physical factors involved include, malalignment of the kneecap, weakness of the thigh muscles, tightness of the hamstring muscles, and obesity.  Arthritic conditions can also contribute to the pain.  Patellofemoral symptoms can be similar to those of meniscus tears and even ACL tears.  The vast majority of patients get significant relief from performing appropriate stretching and strengthening exercises in addition to weight loss when indicated.  Occasionally, bracing can help, and very rarely, surgical procedures to realign the patella are necessary.  Sometimes the knee cap (patella) will dislocate or slip out of position.  Usually it will go back in place on its own although sometimes it will need to be put back in place.  Non-surgical treatments like those above are often successful.  If the kneecap is still unstable, surgical treatment can typically resolve the problem of recurrent dislocation.

Articular Cartilage Injury

The articular cartilage covers the end of the bone bones and allows the bones to glide smoothly past one another and provides cushioning as we bear weight on them.  The tissue is very inactive biologically and has an extremely limited ability to heal itself when damaged.  The wearing away of this covering over time creates the condition we know as arthritis.  Acute injuries can also damage the articular surface.  A piece of cartilage with the bone underneath it (osteochondral injury) or without (chondral injury) can be broken off and irritate the knee.  The body has limited ability to sponataneously heal these injuries.  The injury can occur by itself or with other injuries.  The knee usually becomes painful and swollen.  Often the knee will lock, catch, or click afterwards.  If the piece detaches from its bed, it can move around inside the knee which can often be felt.  Treatment options include resting the knee followed by rehabilitation or surgery to repair the damage and/or remove the loose fragment.  These procedures may be done arthroscopically or open depending on the type, severity, and exact location of the damage.


A microfracture procedure is performed when a focal area of articular cartilage is damaged and there is very little if any surrounding arthritis.  The surgeon makes small holes in the bone to allow local bleeding and scarring filling in the defect left by the damaged articular cartilage.  Recovery can take 3-4 months and there is often an initial period of no weight bearing on the affected leg, usually 6 weeks.  During this period, knee the patient works on knee motion and starts to work on leg strength.  When the non-weight bearing period is over the patient resumes their day-to-day activities and continues to progress with exercising and can usually return to all of their normal activities.

ACI – Articular Cartilage Implantation

ACI is a technique were in an initial surgery, healthy cartilage is harvested from a special non-critical area of the knee and sent to a lab to be processed.  The cartilage cells are isolated and multiplied and in a second procedure implanted into the articular cartilage defect to fill the void left by the damaged cartilage.  This technique is indicated for a larger focal area of damage to the articular cartilage.  The recovery is similar to microfracture.

Osteochondral Graft

An osteochondral graft can be used to treat a chondral or osteochondral injury.  The graft can be taken from a special area in the patients own knee (autograft) or specially prepared organ donor tissue (allograft).  A synthetic graft is being evaluated and shows early promise.  The damage area is cored out leaving a hole which is filled with the graft which is selected to match as closely as possible.  The recovery is similar to microfracture.

Osteochondral Repair

An osteochondral injury can sometimes be repaired if the loose fragment has a good bone bed and the cartilage is still intact.  The fragment can be reimplanted or fixed in place if it has not moved.  Usually, the pieces are held in place with either metal screw(s) buried into the bone and/or absorbable pins.  If the lesions heal well then grafting can be avoided.  Recovery is similar to microfracture.