Chondromalacia Patellae Flashcards
Definition/Description
Chondromalacia patellae (CMP) is referred to as anterior knee pain due to the physical and biomechanical changes . The articular cartilage of the posterior surface of the patella is going though degenerative changes which manifests as a softening, swelling, fraying, and erosion of the hyaline cartilage underlying the patella and sclerosis of underlying bone.
Chondromalacia patellae is one of the most frequently encountered causes of anterior knee pain among young people. It’s the number one cause in the United States with an incidence as high as one in four people.[4] The word chondromalacia is derived from the Greek words chrondros, meaning cartilage and malakia, meaning softening. Hence chondromalacia patellae is a softening of the articular cartilage on the posterior surface of the patella which may eventually lead to fibrillation, fissuring and erosion.
The differential diagnosis of chondromalacia include patellofemoral pain syndrome and patellar tendinopathy. Chondromalacia is are not considered to be under the umbrella term of PFPS. The pathophysiology is thought to be different and therefore there is alternative treatment
Clinically Relevant Anatomy
The knee comprises of 4 major bones: the femur, tibia, fibula and the patella. The patella articulates with the femur at the trochlear groove. Articular cartilage on the underside of the patella allows the patella to glide over the femoral groove, necessary for efficient motion at the knee joint. Excess and persistent turning forces on the lateral side of the knee can have a negative effect on the nutrition of the articular cartilage and more specifically in the medial and central area of the patella, where degenerative change will occur more readily.
The quadriceps insert into the patella via the quadriceps tendon and are divided into four separate muscles: rectus femoris (RF), vastus lateralis (VL), vastus intermedius (VI) and vastus medialis (VM). The VM has oblique fibres which are referred to the vastus medialis obliques (VMO
These muscles are active stabilisers during knee extension, especially the VL (on the lateral side) and the VMO (on the medial side). The VMO is active during knee extension, but does not extend the knee. Its function is to keep the patella centred in the trochlea. This muscle is the only active stabiliser on the medial aspect, so it’s functional timing and amount of activity is critical to patellofemoral movement, the smallest change having significant effects on the position of the patella.
Not only do the quadriceps influence patella position, but also the passive structures of the knee. These passive structures are more extensive and stronger on the lateral side than they are on the medial side, with most of the lateral retinaculum arising from the iliotibial band (ITB). If the ITB is under excessive tension, excessive lateral tracking and/or lateral patellar tilt can occur. This is can be as a result of the tensor fasciae lata being tight, as the ITB itself is a non contractile structure.
Other significant anatomical structures:
Femoral anteversion [13] or medial torsion of the femur is a condition which changes the alignment of the bones at the knee. This may lead to overuse injuries of the knee due to malalignment of the femur in relation to the patella and tibia.
The Q-angle: or quadriceps angle is the geometric relationship between the pelvis, the tibia, the patella and the femur [14] [15] and is defined as the angle between the first line from the anterior superior iliac spine to the centre of the patella and the second line from the centre of the patella to the tibial tuberosity
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If there is an increased adduction and/or internal rotation of the hip, the Q-angle will increase, which increases the relative valgus of the lower extremity as well. This higher Q-angle and valgus will increase the contact pressure on the lateral side of the patellofemoral joint (which is also increased by external rotation of the tibia)
Epidemiology /Etiology
The etiology of CMP is poorly understood, although it is believed that the causes of chondromalacia are injury, generalised constitutional disturbance and patellofemoral contact , or as a result of trauma to the chondrocytes in the articular cartilage (leading to proteolytic enzymatic digestion of the superficial matrix). It may also be caused by instability or maltracking of the patella which softens the articular cartilage.
Chondromalacia patella is usually described as an overload injury, caused by malalignment of the femur to the patella and the tibia
Main reasons for patellar malalignment
Q-angle: An abnormality of the Q-angle is one of the most significant factors of patellar malalignment. A normal Q-angle is 14° for men and 17° for women. An increase can result in an increased lateral pull on the patella.
Muscular tightness of:
> Rectus femoris: affects patellar movement during flexion of the knee.
> Tensa Fascia late; affects the influence of the ITB
> Hamstrings: during running tight hamstrings increase knee flexion which results in increased ankle dorsiflexion. This causes compensatory pronation in the talocrural joint.
> Gastrocnemius: tightness will result in compensatory pronation in the subtalar joint.
Excessive pronation: prolonged pronation of the subtalar joint is caused by internal rotation of the leg. This internal rotation will result in malalignment of the patella.
Patella alta: this is a condition where the patella is positioned in an abnormally superior position. It is present when the length of the patellar tendon is 20% greater than the height of the patella.
Vastus medialis insufficiency: the function of the vastus medialis is to realign the patella during knee extension. If the strength of VM is insufficient this will cause a lateral drift of the patella.[21]
Muscular balance between the VL and VM is important. Where VM is weaker the patella is pulled too far laterally which can cause increased contact with the condylus lateralis, leading to degenerative disease
Stages of the disease
In the early stages, chondromalacia shows areas of high sensitivity on fluid sequences. This can be associated with the increased thickness of the cartilage and may also cause oedema. In the latter stages, there will be a more irregular surface with focal thinning that can expand to and expose the subchondral bone.
Chondromalacia patella is graded based on the basis of arthroscopic findings, the depth of cartilage thinning and associated subchondral bone changes. Moderate to severe stages can be seen on MRI. [
Stage 1: softening and swelling of the articular cartilage due to broken vertical collagenous fibres. The cartilage is spongy on arthroscopy.
Stage 2: blister formation in the articular cartilage due to the separation of the superficial from the deep cartilaginous layers. Cartilaginous fissures affecting less than 1,3 cm² in area with no extension to the subchondral bone.
Stage 3: fissures ulceration, fragmentation, and fibrillation of cartilage extending to the subchondral bone but affecting less than 50% of the patellar articular surface.
Stage 4: crater formation and eburnation of the exposed subchondral bone more than 50% of the patellar articular surface exposed, with sclerosis and erosions of the subchondral bone. Osteophyte formation also occurs at this stage.
Articular cartilage does not have any nerve endings, so CMP should not be considered as a true source of anterior knee pain, rather, it is a pathological or surgical finding that represents areas of articular cartilage trauma or divergent loading. [10] Kok et al showed that there is significant association between subcutaneous knee fat thickness with the presence and severity of chondromalacia patellae. This could explain why women suffer more from the condition chondromalacia than men.
Characteristics/Clinical Presentation
There are important distinguishing features between chondromalacia patellae and Osteoarthritis. CMP affects just one side of the joint, the convex patellar side, with excised patellas show localised softening and degeneration of the articular cartilage. The main symptom of chondromalacia patellae is anterior knee pain, which is exacerbated by common daily activities that load the patellofemoral joint, such as running, stair climbing, squatting, kneeling , or changing from a sitting to a standing position . The pain often causes disability affecting the short term participation of daily and physical activities.
Other symptoms are tenderness on palpating under the medial or lateral border of the patella, crepitation (felt with motion), ; minor swelling, a weak vastus medialis muscle and a high Q-angle. Vastus medialis is functionally divided into two components: the vastus medialis longus (VML) and the vastus medialis obliquus (VMO). The VML extends the knee, with the rest of the quadriceps muscle. The VMO does not extend the knee, but is active throughout knee extension. This component assists in keeping the patella centred in the femoral trochlea.
This condition can cause a deficit in quadricep strength, therefore, building and/or maintaining quadriceps strength is essential. A significant number of individuals are asymptomatic, but crepitation in flexion or extension is often present. Chondromalacia is common in adolescents and females with idiopathic chondromalacia usually seen in young children and adolescents and the degenerative condition is most common in the middle aged and older population
Tests - CRITICAL TEST -
This is done with the patient in high sitting and performing isometric quadriceps contractions at 5 different angles (0°, 30°, 60°, 90° and 120°) while the femur is externally rotated, sustaining the contractions for 10 seconds. If pain is produced then the leg is positioned in full extension. In this position the patella and femur have no more contact. The lower leg of the patient is supported by the therapist so the quadriceps can be fully relaxed. When the quadriceps is relaxed, the therapist is able to glide the patella medially. This glide is maintained while the isometric contractions are again performed. If this reduces the pain and the pain is patellofemoral in origin, there is a high chance of a favourable outcom
