Stronger Quads May Benefit Arthritic Knees | Arthritis Information

Strong quadriceps prevented cartilage loss at the lateral compartment of the patellofemoral joint, but had no influence on loss at the tibiofemoral joint, Shreyasee Amin, M.D., M.P.H., of the Mayo Clinic, and colleagues reported in the January issue of Arthritis & Rheumatism.

"Our results suggest that strong quadriceps muscles have an overall beneficial effect on knee osteoarthritis," the researchers said.

Some studies have found decreased strength in the quadriceps to be associated with greater knee pain and impaired function; others have shown mixed results, the researchers said.

They also noted that most studies have evaluated the effect of quadriceps strength on the tibiofemoral joint of the knee, but not on the patellofemoral joint, a site of frequent cartilage loss.

So to assess how quadriceps strength affects loss of cartilage at both the joints, the researchers recruited 265 patients (154 male) for a prospective 30-month study.

All patients had knee osteoarthritis at baseline, and each underwent an MRI of the knee that had worse pain.

Quadriceps strength was calculated using an isokinetic dynamometer as patients concentrically extended their knees.

Patients were also asked to rate the severity of their knee pain, and physical function was assessed.

All measurements were repeated at 15 and 30 months.

The researchers found no association between quadriceps strength and cartilage loss at the tibiofemoral joint -- neither in the lateral nor medial compartment.

They said their findings were consistent with those of previous studies.

Similarly, no effect was observed in the medial compartment of the patellofemoral joint.

However, greater strength was protective against cartilage loss at the lateral compartment of the patellofemoral joint (OR 0.4, 95% CI 0.2 to 0.9 for high strength and OR 0.5, 95% CI 0.2 to 1.1 for middle strength).

The researchers said the effect may be explained by a stronger vastus medialis obliquus -- the quadriceps muscle that pulls the knee inward by pulling the patella medially in the femoral trochlea. This may stabilize the kneecap and help prevent cartilage loss around that part of the joint.

Also, they said, patients who had the highest levels of quadriceps strength had significantly less knee pain and better physical function than those with the weakest muscles (P<0.001).

The researchers noted several limitations to the study, including the possibility of residual confounding by age and BMI. They also noted that there was no measure of knee laxity and they were unable to evaluate the possibility of an interaction between quadriceps strength and activity level.

They pointed out that "the focus of this study was quadriceps strength, and not strengthening or exercise." The researchers said their findings need to be validated in further studies, and that more work is needed before recommending any exercise regimens for knee osteoarthritis patients.