Chondromalacia Patella

                 

                                        DR KS Dhillon

Introduction

Chondromalacia is an affliction of the hyaline cartilage of the articular surfaces of the bone. There is softening and then subsequent tearing, fissuring, erosion, and degeneration of hyaline cartilage. Chondromalacia can occur in any synovial joint. It is, however, most commonly seen in the patellofemoral joint. In the patellofemoral joint, it is called chondromalacia patella, patellofemoral syndrome, or runner's knee. The articular surface of the patella is covered with hyaline cartilage and it articulates with the hyaline cartilage on the femoral groove (trochlear groove). 

Chondromalacia can result from direct trauma, patellar dislocation, chronic patellar instability/subluxation, patella alta, quadriceps imbalance, synovial plicae, and iatrogenic injections of medication. 

Etiology

A common cause of microtrauma leading to wear and tear resulting in chondromalacia patella is lateral subluxation or lateral positioning of the patella. It is more commonly seen in females who have a larger Q angle. 

The Q angle measures the pull of the quadriceps muscle relative to the pull of the patella tendon on the patella.  A normal angle is 17 degrees in women and 14 degrees in men. It is measured by drawing a line from the center of the anterior iliac spine to the center of the patella (quadriceps pull) and a second line from the mid-portion of the patella to the tibial tubercle (patella tendon pull). An abnormally high Q angle indicates lateral pull of the patella in the trochlear groove of the femur which leads to articular cartilage wear and tear [1].

The patella alignment in the vertical plane can also be abnormal. A high riding patella (patella alta) and a low riding patella (patella baja) have also been implicated as a cause of chondromalacia.

Chondromalacia can also result from injuries, immobilization, and surgical procedures that lead to quadriceps atrophy. Quadriceps atropy causes micro-trauma which is created by the decreased pull of the quadriceps muscle on the patella [1].

Lateral synovial plicas have also been implicated in the pathogenesis of chondromalacia patella. Patellofemoral stress caused by sporting activities, repeated stair climbing, and kneeling can contribute to the development of chondromalacia.

Iatrogenic injection of chondrotoxic medications into a joint can lead to chondromalacia patella. Intra-articular injections of bupivacaine and high doses or frequent intra-articular injections of corticosteroid are known to lead to softening and/or articular cartilage dysfunction [1]. 

Pes planus can cause an increased valgus orientation of the knee leading to increased lateral wear of the patellofemoral joint. High-heel shoes can increase stresses on the patellofemoral joint leading to chondromalacia [1].

Epidemiology

Chondromalacia patella is more common in women as compared to men. This is attributed to the presence of increased Q angles in women. There is no known hormonal cause of variation. Active young adults who participate in running sports and workers who have increased patellofemoral stress due to repeated stair climbing and/or kneeling have a higher incidence of chondromalacia.

About 20% of individuals with patellofemoral pain have chondromalacia patella. About 80% of patients with lower limb joint pain have patellofemoral pain [2]. 

History and Physical Examination

The chief complaint of patients with chondromalacia patella is anterior knee pain. The pain is aggravated by activities that increase the stress on the patellofemoral joint. These activities include stair climbing, squatting, kneeling, and running. 

There are several other causes of anterior knee pain. These include patellar tendonitis, infrapatellar fat pad syndrome (Hoffa disease), patellar instability, bi-partite patella, osteochondritis dessicans of the patellofemoral joint, patella alta, patella baja, and synovial plica.

The major symptom of chondromalacia is diffuse pain in the peripatellar or retropatellar area of the knee. The onset of pain is usually insidious and typically vague in nature. The pain is aggravated by daily activities such as going up and downstairs, prolonged sitting with knee bent, squatting, and kneeling.

Physical exam can show quadriceps muscle atrophy, signs of patella maltracking, lateral subluxation of patella or loss of medial patellar mobility, 

increased femoral anteversion or tibial external rotation, positive patellar apprehension test, palpable crepitus, pain with compression of the patella with knee range of motion, or resisted knee extension. 

The Clark’s test specifically evaluates the knee for chondromalacia. This test is performed by compressing the patella into the femoral trochlea and having the patient contract his/her quadriceps muscle. This pulls the patella through the groove and causes anterior knee pain in patients with chondromalacia.

Imaging

Radiographs

Three views of radiographs are recommended namely the AP, lateral, and Merchant’s view. The radiographs can show a shallow sulcus, patella alta/baja, and lateral patella tilt.

CT scan

CT scans are of not much use for the diagnosis of chondromalacia. CT scans can show patellofemoral alignment, fractures, trochlear geometry, and limb torsion.

MRI

MRI is the modality of choice for assessing patellar cartilage.

T1 sequence is a poor sequence for cartilage and surface irregularity and subtle signal change may not be apparent. Areas of hypointensity may be seen in cartilage. Subchondral reactive bone marrow edema pattern (low signal) may be seen.

T2/PD sequences are the best sequences for assessing cartilage. Most patients with chondromalacia patellae will have focally increased signal in the cartilage or focal contour defects in the cartilage surface. Abnormal cartilage is usually of high signal compared to normal cartilage. The findings can range from a subtle increase in signal to complete loss of cartilage. 

The modified Outerbridge grading of chondromalacia is divided into four grades based on T2/PD sequences. 

Grade I: focal areas of hyperintensity with normal contour. 

Grade II: blister-like swelling/fraying of articular cartilage extending to surface.

Grade III: partial-thickness cartilage loss with focal ulceration.

Grade IV: full-thickness cartilage loss with underlying reactive changes in the bone. 

Treatment

Nonoperative

In many individuals with chondromalacia patellae, the symptoms are self-limiting. The treatment is primarily nonsurgical. Conservative therapeutic interventions include the following:

• Isometric quadriceps strengthening and stretching exercises: Restoration of good quadriceps strength and function is important in achieving good recovery [3].

• Stretching exercises. Hamstring, quadriceps, calf, lateral hip, and thigh stretching exercises can be useful.

• Temporary modification of activity. Avoid activities that compress the

patella against the femur with force. This will include avoiding going up and downstairs and hills, deep knee bends, kneeling, step-aerobics, and high-impact aerobics. Do not wear high-heeled shoes. Do not do exercises sitting on the edge of a table and lifting leg weights

• Patellar taping. An elastic knee support that has a central opening cut out for the kneecap can help reduce pain.

• Foot orthoses. Orthotics which decrease pronation of the foot can be useful.

• Non-steroidal anti-inflammatory drugs are more effective than steroids.

Surgical treatment

Surgical management is indicated when there is a failure to respond to nonoperative management. Studies show that up to 20% of athletes fail to improve adequately with conservative treatment [4]. Surgical intervention often produces variable results. 

There are 2 approaches to surgical treatment of chondromalacia:

1.Treatment directed at malalignment and other abnormalities of the extensor mechanism and the patellofemoral joint. 

Treatment directed at malalignment and other abnormalities of the extensor mechanism and the patellofemoral joint include:

• Lateral retinacular release-- This is indicated when there is a tight lateral retinacular capsule, loose medial capsule and there is lateral patellar tilt. This can be carried out by open arthrotomy or arthroscopically. The majority of studies, however, show that over 80% of patients with chronic patellofemoral pain respond initially to lateral release of the patella but with increasing time there is a diminishing long-term benefit [4].
• Patellar realignment surgery- This is indicated when there is patellar malalignment. The following techniques can be used: Maquet anterior tubercle elevation, Fulkerson anterior-medialization for increased Q angle and patella instability, Elmslie-Trillat osteotomy, and medial patellofemoral reconstruction.

2.Treatment of the diseased cartilage.

 Arthroscopic debridement of the cartilage is usually carried out for Outerbridge grade 2-3 chondromalacia of the patellofemoral joint. Krüger et al [5] carried out a retrospective study of 161 patients who had undergone arthroscopic operation for chondromalacia of the knee joint. The average follow-up was 40 (range 10-72) months. They found that patients with severe articular cartilage lesions who had undergone articular lavage alone showed significantly poorer results. Generally, younger patients showed better results than older patients. According to the authors, the literature shows that aggressive subchondral abrasion in severely degenerated knees does not provide any benefits to the patient. They found that almost every second patient suffering from grade 4 chondromalacia complained of recurrent pain 1 year postoperatively. One of every 6 patients received a knee joint prosthesis within the 1st year after debridement surgery. 

Price et al [6] in a series involving cases of post-traumatic chondromalacia patellae found that arthroscopic shaving and lavage generally provided only partial relief of symptoms, and few patients showed improvement beyond 2 years from the date of injury.

Federico et al [7] found that patients with traumatic chondromalacia patellae had 57.9% good or excellent results with joint debridement, and the patients with atraumatic cases had 41.1% good or excellent results with surgery, indicating that many patients who were improved by the surgery still had functional limitations.

Some surgeons have resorted to patellofemoral arthroplasty and others to patellectomy for treatment of advanced chondromalacia of the patella. The clinical outcome after patellectomy is not good with one study showing only 29% of soldiers recovering to a fully fit category after patellectomy [8].

Patellectomy has its own set of problems, which include loss of extension power and increased risk of arthritis in the tibiofemoral compartment. It is hardly carried out nowadays.

Patellofemoral arthroplasty (PFA) is sometimes carried out in patients with severe isolated patellofemoral osteochondropathy not responding to nonoperative measures. The main contraindications for arthroplasty are uncorrected maltracking of the patella, uncorrected tibiofemoral malalignment, and other compartmental diseases. Success rates of PFA vary from 42% to 90% [9,10,11,12]. The published data is limited and the indications for surgery are varied in these studies and this could possibly explain the diversity of these success rates [13].

Other treatments

There are some newer techniques for the treatment of chondromalacia patellae, such as chondrocyte transplant and cartilage transplant. A definite conclusion cannot be drawn on the effectiveness of these techniques in the treatment of chondromalacia because the patients undergoing such treatment have not been followed up for a sufficient length of time [14]. 

Prognosis

Pain from chondromalacia usually disappears with time. Recovery can occur in a month. Sometimes it takes years before it disappears. Teenagers usually achieve long-term recovery because their bones are still growing, and their symptoms generally disappears once they reach adulthood.[15]

Reference

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