eMedicine Specialties > Orthopedic Surgery > Knee
Patellofemoral Arthritis: Treatment
Updated: Sep 12, 2008
Treatment
Medical Therapy
Nonoperative treatment involves nonsteroidal anti-inflammatory drugs (NSAIDs), activity modification, and muscle-strengthening activities. Strengthening of the quadriceps muscle group can be beneficial, especially in patients with maltracking and weakness of these muscles. Activities should be modified so that prolonged flexion (as with squatting) and stair climbing are avoided. A knee sleeve may also relieve symptoms.
Some have advocated taping of the patella to push it into a more medial position, especially in young patients undergoing rehabilitation for anterior knee pain. Interestingly, a recent group who used CT to evaluate patellar position found that taping had absolutely no effect on either patellar displacement or patellar tilt.
A prospective, randomized, double-blind study of nonoperative treatment in younger patients (aged 20-55 y) with patellofemoral pain (not arthritis) revealed that symptoms resolved in 67% of patients within 6 months of initiating physical therapy, and 80% graded their knee as excellent after 7 years. However, clinical findings in these patients worsened with time. Significantly more patients had positive apprehension and compression test results and had crepitus at 7-year follow-up, and 5% of patients developed arthritis. Although conservative management may help in resolving symptoms, no evidence indicates that it prevents the progression of arthritic changes in the joint.
Surgical Therapy
Before proceeding with surgery, the surgeon and patient must be in agreement regarding the goal of the procedure. Malalignment can be corrected, soft tissues can be balanced, and articular damage can be assessed and treated. Arthroscopy can be used diagnostically to assess the size, severity, and location of articular degeneration and to determine whether subluxation of the patella is present.
Arthroscopy
Arthroscopy is an excellent tool for diagnosing patellofemoral arthritis. The surface of the patellofemoral and tibiofemoral joints can be evaluated under direct visualization, and the motion of the patella with flexion and extension can be observed. Arthroscopic debridement has been used to smooth and clean up fibrillated cartilage on the joint surface. No evidence indicates that this provides long-term relief of pain, however. Articular cartilage does not regenerate; instead, it is replaced by fibrocartilage. Although not as mechanically protective as articular cartilage, fibrocartilage may induce less of an inflammatory response than damaged articular cartilage.
Procedures to correct malalignment
For patients with anterior knee pain directly associated with poor patellar positioning, surgical procedures that attempt to correct the malalignment may be beneficial. A lateral retinacular release is performed to change the tilt of the patella, decreasing pressure on the lateral patellar facet by releasing the lateral constraints of the patella. These constraints include the iliotibial band, vastus lateralis, and patellofemoral and patellotibial ligaments. This procedure is often performed with patellofemoral and total knee arthroscopy when lateral patellar malalignment is noted.
Medialization of the tibial tuberosity has been advocated to improve patella tilt and subluxation by decreasing the valgus moment acting on the patella. Anteriorization of the tibial tubercle is used in more severe cases and increases the power of the quadriceps by increasing the length of the lever arm. Patellofemoral joint reactive forces are decreased with this procedure.
The multiple procedures used to correct malalignment indicate that no single procedure consistently results in excellent outcomes. The goal of these procedures is to decrease pain by changing the distribution of force across the patella. They may be beneficial for young patients with intractable knee pain unresponsive to medical therapy or in some patients with early arthritic changes. For patients with severe patellofemoral arthritis, a more extensive surgical procedure is required to address the articular damage.
Cartilage transplantation
The ideal solution to articular cartilage damage is cartilage regeneration. Unlike bone, damaged articular cartilage lacks the ability to repair itself. Techniques such as subchondral drilling, microfracturing, and abrasion arthroplasty have been used to stimulate healing of the articular cartilage in the knee joint. Some have theorized that undifferentiated progenitor cells in the marrow are stimulated to form articular cartilage. Histologic studies, however, have demonstrated that healing of the defect occurs primarily with fibrocartilage, which has inferior mechanical properties compared with those of hyaline cartilage.
Because of the limitations of these techniques, research is currently being undertaken to replace the defect with chondrocytes or osteochondral autografts or allografts to restore the hyaline cartilage of the articular surface.19
Autologous cartilage transplantation and osteochondral autografting
Briefly, the procedure of autologous chondrocyte transplantation involves harvesting chondrocytes from a relatively non–weightbearing portion of the medial tibia condyle. The cells are cultured for 11-21 days, at which time they are implanted into the defect. The defect is covered with a periosteal patch from the proximal medial tibia to keep the cells in place. Patients must be non–weight bearing for approximately 8 weeks to avoid damaging the transplanted cells.
Brittberg et al published their intermediate (39-mo) follow-up on 23 patients with full thickness cartilage defects in the knee that were treated with autologous cartilage transplantation.20 Of 16 patients with femoral condylar defects, 14 (87%) had good-to-excellent clinical results. Transplants to the patella region had less favorable results, with only 2 (29%) of 7 patients having good-to-excellent results. Hyaline cartilage was found on biopsy in 11 of 16 femoral transplants compared with 1 of 7 patellar transplants.
Peterson et al reported that 91% of 58 patients had good-to-excellent results, based on clinical examination and results self-assessment questionnaires.21 In this series, however, all of the patients had femoral condylar defects and none were treated for osteochondral defects of the patella.
The limitations of this type of autologous cartilage transfer include the requirement of 2 surgical procedures, the risk of infection being introduced when the cells are grown in vitro, and the facilities and expertise needed for the successful in vitro growth of chondrocytes. A similar method, autologous osteochondral mosaicplasty is performed to achieve the same results without these limitations.
In this technique, multiple, small (2.7- to 8.5-mm-diameter) plugs of hyaline cartilage and underlying subchondral bone are taken from non–weightbearing surfaces. They are then implanted into the osteochondral defect. The donor site fills with fibrocartilage, but, theoretically, the hyaline cartilage of the transplant should be preserved.
Patients are typically advised not to bear weight for 2 weeks following the procedure, and then partial weight bearing is allowed for 2 weeks. Hangody et al reported results in 831 consecutive patients who underwent this procedure during a 10-year study period. Complications included deep infection (n = 4) and painful hemarthroses (n = 36). Clinical evaluation with standard knee scores indicated good-to-excellent results following mosaicplasty in 92% of femoral (n = 597) procedures, 94% of talar procedures (n = 76), 87% of tibial procedures (n = 25), and 79% of patellar procedures (n = 118). Patients younger than 35 years had better results than those in older patients.22
Bentley et al published a prospective randomized comparison of autologous cartilage transplantation and mosaicplasty.23 At 19-month follow-up, functional assessment revealed that 88% of patients (n = 58) with cartilage transplants and 69% of patients (n = 42) had good-to-excellent outcomes at an average follow-up of 19 months.
Both autologous cartilage transfer and mosaicplasty may hold promise for the treatment of patellofemoral osteochondral lesions. However, results for osteochondral lesions of the patellofemoral joint with these procedures appears to be less favorable than for lesions in the femoral condyles, and the procedures require careful patient selection. These procedures are best suited for young, active patients who have focal degenerative lesions and in whom moderate-to-severe osteoarthritis has not yet developed. Additional surgical procedures to correct misalignment may also be necessary. Patients must be highly motivated and willing to cooperate with prolonged non–weightbearing periods.
Osteochondral allografting
Osteochondral plugs or wafers can also be obtained from allografts, which limit damage to the articular surface and increase the size of defect that can be repaired. Fresh allografts of articular cartilage and subchondral bone are implanted into the defect. The allograft bone is reabsorbed and remodeled, but the transplanted chondrocytes survive.24,25
Chu et al reported their results in 55 consecutive patients.26 About 84% of patients with unipolar transplants, but only 50% with bipolar transplants, had good-to-excellent results. They also reported that 11 (73%) of 15 patients had good-to-excellent clinical results at 10-year follow-up.
Shasha et al reported long-term follow-up results of osteochondral grafting for isolated posttraumatic tibial plateau defects.27 Kaplan-Meier analysis revealed a survival of 95% at 5 years, 80% at 10 years, and 65% at 15 years, with an endpoint of knee arthroplasty, revision of graft, or a Hospital for Special Surgery knee score of <70. Although this technique does not violate the native hyaline cartilage of the knee, fresh allografts must be used, as freezing or other processing destroys the viability of the chondrocytes. This limitation has limited enthusiasm for this procedure because, despite precautions, the risk of bacterial, viral, or fungal disease transmission remained increased with this type of transplant.
Patellectomy
Patellectomy is a surgical option after severe patella fractures. Surgeons have also used this procedure as a treatment for arthritis of the patella. Problems associated with patellectomy include loss of normal knee power and function, quadriceps weakness, and failure to resolve anterior knee pain. Cybex measurements after patellectomy demonstrate significant decreases in the peak torque of the quadriceps muscles, with preservation of normal hamstring function.28 Patellectomy in a rabbit model has been shown to result in arthritis of the tibiofemoral joint.29
Clinically, a retrospective review of 81 patients who underwent patellectomy for osteoarthritis during a 20-year period found that only 53% achieved a good result.30 With time, there was a statistically significant increase in radiologic changes at the tibiofemoral joint consistent with the development of arthritis. A case report of arthroscopic findings in 16 knees with a prior patellectomy showed severe medial compartment and trochlear articular damage in patients aged 22-64 years with a mean follow-up of 15.4 years.31 With progressive degeneration, these patients may later require a total knee arthroplasty (TKA) for arthritis of the knee.
To the authors' knowledge, no large studies reveal whether patellectomy restricts future options for TKA. Joshi et al reported a complication rate of 36% in 19 patients with prior patellectomy compared with 0% in a matched cohort.32
A retrospective matched control study at the Hospital for Special Surgery examined the results of TKA in patients who either did or did not undergo previous patellectomy.33 Only 6 (30%) of 22 patients underwent patellectomy because of osteoarthritis. At 5-year follow-up, standardized knee scores did not differ between the 2 groups of patients. However, patellectomy results did differ depending on the prosthesis used.
Patients with a posterior cruciate ligament (PCL)–sacrificing prosthesis had statistically higher postoperative knee scores than those with a PCL-retaining prosthesis. The subgroup of patients with PCL conservation had more pain, decreased range of motion, and more difficulty ascending stairs. The authors believe that the posterior stabilized implant increases the quadriceps lever arm. Considerable debate exists, however, regarding which implant provides better results after patellectomy, as other earlier groups have reported contradictory findings.
Patellofemoral arthroplasty
In 1955, McKeever performed the first replacement of the patella as an alternative to patellectomy for isolated patellofemoral arthritis. Since that time, the patellar prosthesis has been reengineered multiple times. The most commonly used implants are cemented polyethylene implants. The procedure can consist of a patella resurfacing procedure alone or may include femoral resurfacing and the replacement of the femoral groove with a metal implant. Isolated patellar resurfacing, however, has not been shown to be more effective than total knee replacement (TKR) in the older patient population.34
One significant advantage of arthroplasty over patellectomy is the preservation of the quadriceps function. Disadvantages of this procedure are that it is a technically demanding procedure that is not commonly performed and that second surgery may be needed for TKR if the patient also has tibiofemoral osteoarthritis. Some concern also exists about the effect of particulate metal debris developing in the joint from the metal-backed component, which may be associated with an increased risk of infection.35
Krajca-Radcliffe and Coker reported a retrospective study of 16 total patellofemoral arthroplasties in 13 patients conducted between 1975 and 1992 with a minimum 2-year follow-up and average patient age of 64 years.36 About 88% had good or excellent results, 7 of 13 were pain-free with all activities, and no patients had pain with routine activity. Quadriceps strength was 75% and 100% of the contralateral side. One patient required a revision procedure.
In a larger series of 72 patellofemoral arthroplasties in 65 patients with an average 4-year follow-up, an 85% had good-to-excellent results. However, more than one half of the patients in this series had concurrent unicompartmental knee replacements. Furthermore, the authors reported complications in 14 patients (18%), 5 of whom required a repeat operation.37
Another review of 66 isolated patellofemoral arthroplasty procedures performed over a 10-year period with a 5.5-year average follow-up demonstrated that 16% required revision to a TKA.38
Total knee arthroplasty
TKA is used to treat patients with severe osteoarthritis of the knee that has not improved with medical management and that has become detrimental to a patient's quality of life. It is usually performed in patients older than 60 years, but occasionally younger patients with significant arthritic changes are considered candidates for the procedure.
At the Hospital for Special Surgery in New York, Laskin and van Steijn compared the results of TKA in 53 patients with severe patellofemoral but minimal tibiofemoral arthritis to sex- and age-matched patients undergoing the procedure for tricompartmental knee arthritis.39 All patients had a cemented tricompartmental PCL-sparing prosthesis. Preoperatively, the group with isolated patellofemoral arthritis had statistically significant increases in pain score, and fewer were able to rise from a chair or climb stairs without assistance.
In this study, lateral release was required in 30% patients with patellofemoral arthritis versus 8% in the other group. Postoperatively, 82% of the patients were able to climb stairs, and only 3 complained of anterior knee pain. Average range of motion was 120°. These results were comparable to those in the other group. This study indicates that TKA may be the procedure of choice in older patients with severe patellofemoral arthritis.
Patellar resurfacing versus nonresurfacing in TKA
The need to perform a patella resurfacing procedure at the time of TKA is still being debated. Some surgeons advocate resurfacing in all patients, while others restrict resurfacing to patients with known patellofemoral arthritis. Patellofemoral complications after TKA with patella resurfacing are associated with obesity, metal-backed patellar implants, and noncemented patellar components.40 These complications can include pain, mechanical fracture, loosening, fracture, and maltracking. Retaining the native patella, however, can result in persistent symptoms of anterior knee pain that can compromise the functional ability of the patient. Furthermore, patients with known osteoarthritis in the tibiofemoral knee compartment are at increased risk for arthritis of the patellofemoral joint.
Some surgeons have suggested that patella resurfacing does not have to be performed if the patellar articular cartilage is normal and if no malalignment is present. The results of several small retrospective studies support the practice of selective resurfacing. In a retrospective study of 185 patients with TKR, pain, functional outcome scores, range of motion, or complications did not differ between those undergoing resurfacing and those not (n = 140).41
In a 10-year retrospective follow-up study in 32 knees with a posterior cruciate-retaining Press-Fit condylar TKA and no resurfacing, only 1 patient required later revision for patella resurfacing.42
Several investigators have asserted that no difference exists between resurfacing and retaining the patella in terms of stair-climbing ability or functional outcome.43,44 Furthermore, if the patella is resurfaced and if a complication requiring revision is present, the patella often cannot be resurfaced again because of bone loss. For this reason, some surgeons do not recommend resurfacing in young patients, even when some patellar chondromalacia is present. If the patella is left unresurfaced, the knee system should have an anatomic rather than dome-shaped trochlear groove in the femoral component.
Other orthopedic surgeons believe that a resurfacing procedure should be performed in all patients at the time of a knee arthroplasty. Biomechanically, most prosthetic knees are designed for use with a resurfaced patella.
A study examining the relationship of the patella to different femoral components revealed that retaining the patella results in changes in contact pressures and in the tracking motion in the patellofemoral joint.45 With flexion of 60° or more, the contact areas shifted from a transverse band across the patella to isolated areas of high pressure on both the medial and lateral sides of the patella. The percentage of patellar contact area subjected to contact pressures greater than 5 MPa was significantly greater with all of the tested prostheses compared with the normal knee with flexion >60°. The patella tracked 3-5 mm more laterally once a prosthesis was in place. This finding may help to explain why some patients without patellofemoral arthritis who have a retained patella may have more difficulty climbing stairs postoperatively than those who undergo a resurfacing procedure.
In a prospective series of 40 patients, patients undergoing patellar resurfacing had clinically improved function at a 2-year follow-up in terms of stair climbing and higher functional k scores than those of patients not receiving this procedure.46 One group in Japan, which routinely did not perform resurfacing, assessed results in 60 patients and found that two thirds had rheumatoid arthritis and one third had osteoarthritis. The percentage of patients complaining of postoperative peripatellar pain was higher than that of patients with rheumatoid arthritis (27% vs 12%).47
Boyd and colleagues from Brigham and Women's Hospital in Boston reported the largest retrospective series to date.48 This group examined the results of using an unconstrained, condylar, PCL-preserving prosthesis with and without resurfacing in 891 knees. Patella resurfacing was performed only for specific conditions: loss of cartilage, surface irregularities, and tracking abnormalities. The rate of complications was higher in those without resurfacing than in those with resurfacing (4% vs 12%). Ten percent of patients without resurfacing required revision for patella resurfacing because of chronic pain. Those with inflammatory arthritis were significantly more likely to require revision for patellar pain than those with osteoarthritis (13% vs 6%).
To the authors' knowledge, no large prospective studies currently provide clarity in this debate. Patients with rheumatoid arthritis seem to do better with a resurfacing procedure. To decrease the incidence of a subsequent revision surgery, most patients would most likely benefit from patella resurfacing at the time of TKA. Functional outcomes, however, seem to be similar when selective nonresurfacing is performed.
Follow-up
The type of follow-up care required depends on the type of surgical procedure performed. Postoperative physical therapy focused on quadriceps strengthening is often helpful to many patients. Those undergoing total knee arthroplasty (TKA) or patellofemoral arthroplasty have started range-of-motion exercises immediately after surgery, and, depending on their preoperative ambulatory status, patients may require a short stay in a rehabilitation hospital while they receive physical therapy.
Procedures involving anteriorization of the tibial tubercle require a period of relative immobilization after surgery and before physical therapy. Cartilage transplantation and osteochondral grafts require a period of strict non–weigh bearing for several weeks to allow for the incorporation of the graft. Patient's understanding of and compliance with postoperative treatment protocols are an important factor in the success or failure of all of these surgical treatments.
For excellent patient education resources, visit eMedicine's Arthritis Center. Also, see eMedicine's patient education articles Knee Pain, Osteoarthritis, and Knee Joint Replacement.
Complications
Complications of patellectomy include quadriceps weakness, loss of normal knee function, and failure of the procedure to resolve the patient's pain. Some studies indicate that patellectomy may result in an increased incidence of knee arthritis. If osteoarthritis develops later, the patient may require a second surgery for total knee arthroplasty (TKA), and they may have a greater-than-expected complication rate after this procedure.
Complications of patellofemoral arthroplasty include patellar fracture, infection, and adverse reactions to metal debris in the joint. Revision to a total knee occurs in an average of 16% of patients.
Complications of TKA include the infection, loosening, patella fracture, and periprosthetic fracture.
All surgical procedures have risks associated with anesthesia. The extent of the risk is related to the general medical condition of the patient. Knee surgeries are associated with a risk of deep venous thrombosis, which is reduced with the use of appropriate prophylaxis. Pulmonary embolism from propagation of thrombus after total knee reconstruction (TKR) occurs in less than 1% of patients.
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Kannus P, Natri A, Paakkala T. An outcome study of chronic patellofemoral pain syndrome. Seven-year follow-up of patients in a randomized, controlled trial. J Bone Joint Surg Am. Mar 1999;81(3):355-63. [Medline].
Kerrigan DC, Lelas JL, Karvosky ME. Women''s shoes and knee osteoarthritis. Lancet. Apr 7 2001;357(9262):1097-8. [Medline].
McAlindon T, Zhang Y, Hannan M, et al. Are risk factors for patellofemoral and tibiofemoral knee osteoarthritis different?. J Rheumatol. Feb 1996;23(2):332-7. [Medline].
Minas T, Nehrer S. Current Concepts in the Treatment of Articular Carilage Defects. Orthopaedics. 1997;20:525-538.
Nicol SG, Loveridge JM, Weale AE, Ackroyd CE, Newman JH. Arthritis progression after patellofemoral joint replacement. Knee. Aug 2006;13(4):290-5. [Medline].
Post W, Fulkerson J. Arthritis of the patellofemoral joint. Knee Surg. 1:995-1023.
Further Reading
AAOS clinical guideline on osteoarthritis of the knee (phase II).
American Academy of Orthopaedic Surgeons - Medical Specialty Society. 2003. 15 pages. NGC:003374
Review criteria for knee surgery.
Washington State Department of Labor and Industries - State/Local Government Agency [U.S.]. 1991 Jan (revised 2004 Jan). 7 pages. NGC:003482
Total knee replacement.
National Institutes of Health (NIH) Consensus Development Panel on Total Knee Replacement - Independent Expert Panel. 2004 Feb 17. 18 pages. NGC:003622
Imaging after total knee arthroplasty.
American College of Radiology - Medical Specialty Society. 2006. 7 pages. NGC:005538
Keywords
patellofemoral arthritis, anterior knee pain, chondromalacia patellae, osteoarthritis, arthritis of the patella, arthritis of the kneecap, patellofemoral pain syndrome, patellofemoral pain, kneecap, joint disease, chondromalacia, knee pain, patellofemoral syndrome, patellofemoral joint syndromes, total knee arthroplasty, TKA, total knee reconstruction, TKR
