Management of patellofemoral osteoarthritis

                  Management of patellofemoral osteoarthritis

                                   Dr KS Dhillon FRCS
 

Patellofemoral anatomy

The patella is the largest sesamoid bone in the body and is embedded in the quadriceps extensor mechanism of the knee. It is shaped in the form of an inverted triangle. The anterior surface is convex and its posterior is covered with three articular facets which articulates with the femoral trochlear groove on the anterior surface of the femoral condyles. The patella has two large articular facets, the broader lateral articular and narrower medial articular facets and a small medial odd facet. The medial and lateral articular surfaces are concave in shape and are separated by a vertical ridge. The distal quarter of the patella is nonarticular.

The trochlear groove consists of the anterior surface of the medial and lateral femoral condyles with depression in between the two condyles. The lateral condyle is more prominent and projects anteriorly.

The main knee extensors are the rectus femoris and the vastus intermedius, both of which are attached to the superior pole of the patella. The rectus femoris is attached anteriorly and the vastus intermedius is attached more posteriorly at the superior pole of the patella. Distally the patella gives attachment to the patella tendon. The vastus medialis and vastus lateralis provides dynamic stability to the patella in the trochlear groove. The vastus medialis provides medial and the vastus lateralis provides lateral stability. Static stability on the medial side is provided by the medial patellofemoral and patellotibial ligaments and the medial retinaculum while on the lateral side it is provided by the lateral patellofemoral and patellotibial  ligaments and the retinaculum (1).

Incidence of patellofemoral OA

Davis et al (2) reported a radiological incidence of 9.2% of isolated patellofemoral OA in patients older than 40 years of age. They also found a high incidence of isolated patellofemoral OA in men. The incidence of patellofemoral OA in men older than 60 years was 15.4% and in women over 60 years of age, the incidence was 13.6%. They also found that the lateral view of the patellofemoral joint had only 66% sensitivity in detection of OA. A skyline view is essential for detection of OA of the patellofemoral joint. The predictive value of a lateral x ray is only about 52%.

McAlindon et al (3) studied 273 subjects with knee pain and 240 controls and they found OA of the knee in 52% of symptomatic subjects and in 17% of asymptomatic subjects. Isolated OA of the patellofemoral was found in 24% of females and 11% of males older than 55 years with symptomatic knee arthritis.In this study AP and lateral radiographs were obtained and no skyline views were taken. The incidence of patellofemoral OA would have been higher if skyline  views were obtained.

Stefanik et al (4) studied the prevalence of patellofemoral joint (PFJ) and medial tibiofemoral joint (TFJ) OA using magnetic resonance imaging in a cohort of 970 subjects from the Framingham OA study group. They found that PFJ damage was more common than TFJ damage from OA and when there was a mixed pattern , the PFJ damage was more severe. In patients with knee pain the incidence of PFJ OA was as common as TFJ OA.

Etiology of patellofemoral OA

Several factors which alter the biomechanics of the patellofemoral joint can lead to osteoarthritis. Some of this include, trochlear dysplasia, patella alta, lateral subluxation of the patella, increased Q angle, contracted lateral retinaculum, vastus medialis hypoplasia and weakness, absent medial patellofemoral ligament and patellofemoral malalignment. Other predisposing factors include micro and macro trauma, body weight and inherent poor quality of the articular cartilage (5).

Treatment of patellofemoral osteoarthritis

A. Conservative management

 Isolated patellofemoral osteoarthritis is treated conservatively in most patients.

Medications

The role of nonsteroidal medications in the treatment of osteoarthritis is well established. Nonsteroidals are often used to treat the pain and the inflammation in the joint. Persistent synovitis with joint effusion can be treated with joint aspiration and steroid injections. The evidence for use of viscosupplement injections in the treatment of patellofemoral OA is very weak (6).

Physiotherapy

Quadriceps muscle strengthening exercises and strengthening of vastus medialis when there is hypoplasia or weakness of the muscle is usually recommended. Activity modification which reduces the stresses on the patellofemoral joint is also recommended. Activities such as going up and down stairs, squatting, jumping and kneeling increases stress on the patellofemoral joint and patient are advised to avoid such activities.

However, Quilty et al (7)  in a randomised controlled trial found that physiotherapy did not provide long term benefit in patients with patellofemoral OA. They provided physiotherapy in the form education, quadriceps and functional exercise and patella taping in one group and no physiotherapy in the other group. They found that at 5 months there was slight reduction of pain and significant increase in quadriceps strength in physiotherapy group and at 1 year there was no difference between the two groups. The recommendation for this treatment remains weak (6).

Taping and braces

Cushnaghan et al (8) carried out a randomised, single blind, crossover trial of 3 types of patella taping (medial, lateral or neutral) and they found that medial patella taping provided a 25% reduction in knee pain. According to GRADE, the quality of the evidence in this study is moderate but recommendation for such treatment is weak (6).
 Patella braces have also not been found to be useful in the treatment of patellofemoral OA (9).

B. Surgical treatment

Arthroscopy and joint debridement

There are no studies which have addressed arthroscopic joint debridement as a mode of treatment  for patellofemoral OA. However there is high level evidence that there is no benefit of arthroscopic joint debridement in the treatment of patients with OA of the knee (10 and 11). Based on these studies there is a strong recommendation against the use arthroscopic treatment for patellofemoral OA (6).

Osteochondral allografts

The evidence to support the use of osteochondral allografts for treatment of patellofemoral OA appears to be weak. The studies which claim improved knee function following the use of osteochondral allografts are retrospective case series with level IV evidence (12 and 13).

Resection arthroplasty of patella and partial lateral facetectomy

Beltran (14) in 1987 reported the outcome of resection arthroplasty of the patella in 20 patients (33 knees) with patellofemoral OA. He found that 60% of the patients were painfree at an average of 31 month follow up. The report was based on a personal series patients operated on by the author.
Yeran et al (15) reported the outcome of partial lateral facetectomy of the patella for isolated patellofemoral OA in 11 patients with an average age of 62 years. At an average of 8 years follow up, the average knee score improved from 150 to 176 and the procedure was useful for pain relief. This was a case series with level IV evidence.

Becker et al (16) studied the outcome of a combination of lateral facetectomy, lateral release and medialization of tibial tubercle in 50 patients with isolated patellofemoral OA. At a mean follow up of 7 months they found an improvement in pain score in majority of the patients but the functional outcome was not encouraging. They concluded that they would not recommend this combination of surgical procedures for patients with isolated patellofemoral OA. According to GRADE the evidence for excision arthroplasty of the patella and lateral facetectomy as a form of treatment for isolated patellofemoral OA is weak (6).

Lateral retinacular release and anteromedialization of tibial tubercle

Alemdaroglu et al (17) showed a decrease in pain levels at 3 months in patients with grade 2 to 4 chondral lesions in middle aged and elderly patients with lateral release and patellofemoral joint debridement. The pain levels remained the same over the next 12 months.

Aderinto and Cobb (18) reviewed 50 patients who had lateral release for patellofemoral OA (53 knees) at an average follow up of 31 months. Four patients had a knee replacement during the follow up period. Of the remaining 49 knees, 80% had a reduction in pain, 16% had no change and in 4% the pain was worse. The patient satisfaction outcome was not that good with 33% very satisfied, 26% satisfied and 41% were dissatisfied with their knee.

Carofino and Fulkerson (19) published a retrospective study involving 17 patients (22 knees) over the age 50 years who had anteromedialization of the tibial tubercle for patellofemoral OA.The mean follow up was 77 months and the minimal follow up was 2years. Eight two percents of patients completed the follow up survey. The mean postoperative Lysholm score was 83 and based on these score there were 12 good to excellent, 6 fair, and 1 poor outcomes. The authors concluded that ‘anteromedialization of the tibial tubercle is a definitive treatment option for isolated patellofemoral arthritis in active older patients’.

Atkinson et al (20) studied the outcome of tibial tubercle advancement using a bone graft in 40 consecutive patients (50 knees) with patellofemoral OA. At an average of 81 months (range 26-195 months) follow up the ‘clinical outcomes were rated excellent/good in 77%, fair in 35% and poor in 8% of knees’.Major complication rate was high at 12%.

However in these studies the level of evidence remains of low quality and recommendation for such intervention remains weak (6).

Patellofemoral arthroplasty

Patellofemoral replacement was first introduced by McKeever in the form of a patella shell in 1955 and a total patellofemoral arthroplasty was introduced in 1979 (5). Earlier designs had relative high failure rate. However the newer designs have showed more promising results.Good to excellent results at 3 to 17 years in about  two third of the patients have been report by several studies.
Kooijman et al (21) reported the outcome of 1st generation PFJ replacements (56) in 51 patients at a mean follow up of 15 years. They had an early reoperation rate of 18% and a revision rate of of  15.5% which were related to the prosthesis. Thirty percent more knees had to be revised because of progression of tibiofemoral OA. The rest of the patients did well at 15 years follow up.

There were several other studies of 1st generation PFJ replacements with mid to long term follow up which showed high reoperation rates (26% to 63%) and high revision rates (19% to 51%) (22 and 23).

Ackroyd and Chir (24) published the 2 to 5 years follow up results of newer design patellofemoral arthroplasties in 240 patients (306 knees). There was progression of tibiofemoral OA in 5% and revision was necessary in 3.6% of the patients. Persistent knee pain was reported in 4% of the patients.

Ackroyd et al (25) reported their midterm results of the Avon patellofemoral arthroplasty in 2007.The 5 years survival was 95.8% and results were successful as judged by the Bristol pain score in 80% of the patients. Radiological progression was reported in 28% of the patients.

The Australian joint registry (26) reported a 9.9% revision rate with the Avon prosthesis and  and the overall revision rate for the patellofemoral arthroplasty was 15%.

Despite some promising results, according to GRADE, ‘the evidence is of low quality, with a weak recommendation for use of this intervention’ (6).

Total knee arthroplasty

There are several studies published which show that a total knee replacement with patella resurfacing gives satisfactory 5 to 7 years results for isolated patellofemoral OA. Meding et al (27) showed good results in 27 patients with an average age of 52 years who had total knee replacement for patellofemoral OA at an average of 6.2 years follow up. None of the patients had complications and they questioned the need for patellofemoral arthroplasty which is associated with more complications.

Dalury (28) showed good results in 25 patients (33 knees) after total knee replacement for patellofemoral OA at an average of 5.2 years follow up.The average knee score at final follow up was 96 (preop 62). The results appear to be similar to that after knee replacement for tibiofemoral OA (27). One fifth of patients after total knee replacement continue to have anterior knee pain (27, 29, 30).

 Thompson et al (31) published an interesting study in 2001 which showed good to excellent results at a mean of 20 months follow up in 33 patients with patellofemoral OA who had knee replacement without patella resurfacing. None of the patients had a revision at the last follow up. During knee replacement the need for patellar resurfacing in tricompartmental OA and patellofemoral OA remains unanswered.

Despite the good outcome of knee replacement in patients with patellofemoral OA, the evidence according to GRADE,is of low quality and the recommendation for a total knee replacement as a mode of treatment for patellofemoral OA remains weak (6).

Patellectomy

Treatment of advanced patellofemoral OA in young patients, which is not responding to conservative treatment, can be a challenge. A total knee replacement may be suitable for elderly patients with advanced patellofemoral OA but it will not be a suitable option in young patients due limited lifespan of replacement arthroplasties.

Traditionally patellectomy has had a chequered past over the last 100 years due to  poor results caused by weakness of the extensor mechanism. However there have been some reports of good outcome after patellectomy.

Compere et al (32) in 1979 published a retrospective study in which they reported the results of patellectomy in 26 patients (29 knees). When performing the patellectomy they maintained the continuity of the extensor mechanism and at the same time they advanced the vastus medialis. They reported good to excellent in 90 per cent of the patients. There were two cases with extension lag and the average knee flexion was 118 degrees. There was minimum quadriceps atrophy with good strength.

Baker and Hughston (33) published the outcome of Miyakawa patellectomy, in 17 patients (20 knees), who had patellofemoral OA or chondromalacia or both due to malfunction of the extensor mechanism. While performing the Miyakawa patellectomy, the extensor mechanism is realigned with proper tension, thereby centering the functional pull of the quadriceps tendon and patellar ligament.The void left by the patellectomy is filled with a superficial strip of the quadriceps tendon which is pulled distally. At the same time the the musculotendinous portions of the vastus medialis and lateralis are advanced over the defect left by the patellectomy and sutured to the quadricep tendon. At an average follow-up was 13.8 years (range, 3.6 to 31.7 years), 19 of the 20 knees had good to excellent subjective results and 18 had good to excellent objective results.

Asopa et al (34) reported the outcome of a new tension preserving surgical technique to reconstruct the extensor mechanism after patellectomy for patellofemoral OA. They resected the patella with the extensor expansion by incising the quadricep tendon at its junction with the patella and the patella tendon at its junction with the patella. They then sutured the quadricep tendon to the patella tendon with interrupted sutures. The knee was immobilized with a removable knee splint. They performed 8 patellectomies in patients with an average age of 38 years and the average follow up period was 11 years. All patients obtained pain relief and the outcome was better in patients with patella disease alone as compared to those with patella and trochlear disease. All patients had full or near full extension.

There is no robust evidence in literature to support the use of patellectomy for the treatment of patellofemoral OA. However its use in young patients with advanced PF OA may be justified.

Conclusion

Patellofemoral OA is not uncommon with an incidence of about 10% in individuals below 40 years and about 15% in those above 60 years of age. The etiology is multifactorial and treatment is controversial and challenging. Conservative treatment consists of NSAIDs, physiotherapy, taping and bracing. Surgical options include, arthroscopy and debridement,lateral release, medialization of the tibial tubercle, partial facetectomy, resection arthroplasty, patellofemoral arthroplasty, total knee replacement and patellectomy. However the evidence in literature to support any one of these treatments is of low quality and the evidence for recommendation of these interventions for treatment patellofemoral OA is weak.

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