Bipartite Patella (Knee Flexion Deformity)
What is bipartite patella?
A knee flexion deformity is the inability of a knee to move through its normal range of motion, or fully straighten. It is also referred to as flexion contracture. The normal active range of motion of the knee is between 0 degrees extension and 140 degrees flexion. People with flexion deformity have either or both reduced. In most cases, flexion deformities occur bilaterally. Treating a knee flexion deformity requires extensive rehabilitation.
A bipartite patella forms when a portion of patella (kneecap) fails to heal completely along the bony edges of the patella. It mostly occurs in the upper and outer portion of the patella. It is presented in form of an accessory ossification centre at the superolateral pole (‘Partite’ refers to being divided into parts). The condition is usually asymptomatic, and is detected when a person experiences problems from another underlying condition.
What are the causes of the disorder?
The patella is the largest sesamoid bone in the body and humans have the capacity to bring the knee to near full extension; the patella in this situation is out of the confines of the trochlea and is susceptible to instability. Knee flexion deformity results when the knee flexors are unable to lengthen along with the bone.
Flexion deformity may result from joint destruction and ankylosis or from a situation wherein the joint anatomy and mobility are preserved. This is caused by blockage of movement caused by a piece of bone or tissue or scar tissues that restrict movement. The usual fibrous connection between the two portions of bipartite patella is disrupted and fails to heal quickly. Most commonly, bipartite patella results from an injury, as seen in athletes who are prone to sustaining contact to their knees (e.g. soccer).
What does one need to know about symptoms or signs?
Most cases of bipartite patella do not showcase any symptoms. However, when present a knee flexion deformity is experienced as:
- Localised pain over the anterior knee
- Inability to extend the knee completely
- Pain with high level activity or deep squats
- Pain when the bipartite portion of the patella is tapped upon
- A bent-knee gait, limping while walking; muscle fatigue
- Inability to walk long distances or carry heavy weights
People with bipartite patella find it difficult to carry out many daily functional activities, as they require more energy than before. Increased strain resulting from the bent-knee gait leads to weakness in the quadriceps muscles.
Which specialist should be consulted in case of signs and symptoms?
People experiencing symptoms similar to those of bipartite patella must consult an orthopaedic specialist, a doctor who specialises in the treatment of bone disorders.
What are the screening tests and investigations done to confirm or rule out the disorder?
Bipartite patella is diagnosed through:
- Physical exam – The doctor will check the affected knee by tapping on the area to reproduce pain symptoms and ask the patient to move his/her leg in different directions and to various degrees to assess range of motion.
- Imaging tests – An x-ray can provided an image of the patella region and identify any abnormalities.
What treatment modalities are available for management of the disorder?
Treatment for bipartite patella includes:
- Medication – For minor cases that develop from overuse, doctor may recommend anti-inflammatory medication to reduce any swelling and ease the pain. However, more severe pain may require corticosteroid injections.
- Rest/immobilisation – The patient is asked to avoid activities and sports that irritate the patella and place stress on the patellofemoral joint. Placing the affected knee in casts or braces prevents further deformity.
- Arthroscopy – Patients whose movements are severely limited and do not improve with rest and pain medication, an arthroscopic excision of the bipartite patella is recommended. A small incision is made in the patella region and a lighted tube with a small camera at its tip is inserted to reach the affected area. Other instruments are then inserted and the obstructing fragment is removed.
- Physical therapy – Exercises that include a passive range of motion exercise, manual stretching and joint mobilisation prove useful in relieving the pain symptoms associated with knee flexion deformity and aiding recovery.
- Surgery – More severe cases require surgical intervention. This includes soft tissue release, removal of a part of the bone (osteotomies), femoral shortening or hamstring lengthening to relieve the excessive contracture.
What precautions or steps are necessary to stay healthy and happy during the treatment?
Arthroscopic treatment allows a patient to begin early range of motion, weight bearing and slowly increase function to regain normal activity levels.
How can the disorder be prevented from happening or recurring?
Flexion knee deformity can be prevented by keeping joints active and putting them through their full range of active and passive movements. This also helps in good recovery in patients dealing with the condition.
“Bipartite patella,” Radiopaedia.org, Dr Henry Knipe and Radswiki et al., http://radiopaedia.org/articles/bipartite-patella
“The general method for contractures,” http://www.meb.uni-bonn.de/dtc/primsurg/docbook/html/x9543.html