Patellar Dislocation and Subluxation

Description

Patellar dislocation and subluxation are injuries to the kneecap (patella) that affect the joint it forms with the thigh bone (femur). The patella is a V-shaped convex bone that sits within a V-shaped concave groove of the femur, known as the trochlea. Patellar dislocation is a condition in which the patella is displaced from its normal position and no longer sits in the trochlea. Patellar subluxation is a condition in which the patella is not centered within the trochlea, but the joint surfaces still touch; thus the patella is not in normal relationship to the trochlea. This tends to occur in adolescents and young adults.

Common signs and symptoms

• Severe pain when attempting to move the knee and a feeling of the knee giving way

• Tenderness, swelling, and bruising of the knee

• Numbness or paralysis below the dislocation from pinching, cutting, or pressure on the blood vessels or nerves (uncommon)

• Often, patellar dislocation to the outer side of the knee, causing an obvious deformity; often relocates on its own when the knee is straightened, leaving no deformity, however, damage is the same in both cases.

• A lump on the inner knee, at the end of the inner part of the thigh bone (femur)

Causes

• A direct blow to the knee

• A twisting or pivoting injury to the lower extremity, such as with rapid changes of direction

• Powerful muscle contraction

• Congenital abnormality (birth defect), such as shallow or malformed joint surfaces

Factors that increase risk

• Participation in contact sports (football, soccer), sports that require jumping and landing (basketball, volleyball), or sports in which cleats are worn

• A wide pelvis, knocked knees, or shallow or malformed joint surfaces

• Previous knee sprains or patellar dislocations

• Poor physical conditioning (strength, flexibility)

Preventive measures

• Appropriately warm up and stretch before practice and competition.

• Maintain appropriate conditioning that includes thigh, leg, and knee strength, flexibility and endurance training, and cardiovascular fitness.

• For jumping (basketball, volleyball) or contact sports, protect the patella with supportive devices, such as elastic bandages, tape, braces, knee sleeves with a hole for the patella and a built-up outer side or straps to pull the patella inward, or kneepads.

• For sports that require cleats or spikes on the athletic shoe, use cleats or spikes of appropriate length for the sport and the turf or field conditions.

Expected outcome

With appropriate repositioning of the joint (reduction) and treatment, complete healing requires at least 6 weeks.

Possible complications

• Associated fracture or joint cartilage injury as a result of the dislocation or reduction (repositioning) of the patella

• Damage to nearby nerves or major blood vessels (rare)

• Prolonged healing or recurrent dislocation if activity is resumed too soon

• Excessive bleeding within the knee as a result of dislocation

• Patella pain and giving way, usually because of inadequate or incomplete rehabilitation

• An unstable or arthritic joint following repeated injury or delayed treatment

General treatment considerations

After immediate repositioning of the bones of the joint, treatment consists of ice and medications to relieve pain. Reduction can be performed without surgery, although surgery may be necessary to remove loose fragments of bone or cartilage caused by the dislocation or reduction or to help prevent further dislocation. Elevating the injured knee at or above heart level helps in reducing swelling. Your doctor may drain the blood from your knee, and immobilization by splinting or casting or bracing without immobilization for up to 6 weeks may be recommended to protect the joint while the tissues heal. After immobilization, stretching and strengthening of the injured, stiff, and weakened joint and surrounding muscles are necessary because of the immobilization and the injury. These exercises may be done with or without the assistance of a physical therapist or athletic trainer.

Medication

• Nonsteroidal antiinflammatory medications, such as aspirin and ibuprofen (do not take for 7 days before surgery), or other minor pain relievers, such as acetaminophen, are often recommended. Take these as directed by your physician, and contact your doctor immediately if any bleeding, stomach upset, or signs of an allergic reaction occur.

• Strong pain relievers may be prescribed as necessary. Use these only as directed, and take only as much as you need.

Heat and cold

• Cold is used to relieve pain and reduce inflammation for acute and chronic cases. It should be applied for 10 to 15 minutes every 2 to 3 hours as needed and immediately after any activity that aggravates your symptoms. Use ice packs or an ice massage.

• Heat may be used before performing stretching and strengthening activities prescribed by your physician, physical therapist, or athletic trainer. Use a heat pack or a warm soak.

When to call your doctor

• Pain, tenderness, or swelling worsens despite treatment.

• You experience pain, numbness, or coldness in your foot.

• A blue, gray, or dusky color appears in your toenails.

• Any of the following signs of infection occur after surgery: fever, increased pain, swelling, redness, drainage, or bleeding in the surgical area.

• New, unexplained symptoms develop. Drugs used in treatment may produce side effects.

Figure 1

Range of Motion and Stretching Exercises

Patellar Dislocation and Subluxation: Phase I

First-time dislocations: For up to 6 weeks after an initial patella dislocation or subluxation, you may be placed in a knee immobilizer so that the injured tissues can begin to heal. This type of immobilizer will usually keep your knee completely straight. Sometimes your physician will allow some motion in a brace that has hinges, or you will be allowed to come out of your brace to bend and straighten your knee. If this is the case, follow your physician’s specific instructions.

Once you are allowed to start moving your knee, these are some of the initial exercises you may use to start your rehabilitation program, until you see your physician, physical therapist, or athletic trainer again, or until your symptoms resolve.

Chronic or repeated dislocations or subluxations: The person who suffers from chronic or repeated patellar dislocations or subluxations will often not be placed in an immobilizer; rather, the individual is allowed to begin to bend and straighten the knee as much as is comfortable. Please remember:

• Flexible tissue is more tolerant of the stresses placed on it.

• A gentle stretching sensation should be felt.

Range of motion knee flexion

1. Lie on your back with your legs out straight.

2. Bend your knee slowly, and slide your heel toward your buttocks. Bend your knee as far as is comfortable to get a stretching sensation.

3. Hold this position for ____ seconds, and slowly return your leg to the starting position.

4. Repeat this exercise ____ times, ____ times per day.

Range of motion knee flexion/extension

1. Sit on the edge of a table or chair.

2. Use your uninjured leg to straighten (extend) and bend (flex) the injured leg.

3. Flexion: Cross your ankles, placing the uninjured leg on top of the injured leg. Pull your heels backward under the surface you are sitting on to increase the bend in your knee.

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