Are Squats and Lunges Safe in the Rehabilitation of Patients with Patellofemoral Pain?

OBJECTIVES: Patello-femoral pain is a common presenting complaint in orthopaedic clinics, and initial management often involves exercise and quadriceps strengthening regimes. Squats and lunges have become a common part of physiotherapy regimes as well as many exercise programs. It has been our observation that some patients experience a deterioration in pain after starting squats and lunges, and there is no agreement about the safe use of these exercises. The aim of this paper is to review the clinical and biomechanical literature to assess the safety of squats and lunges of patients with patella-femoral or anterior knee pain. METHODS: Systematic Review. A literature review was performed of the Pubmed and PEDro databases using a pre-defined search strategy. Titles were screened by both an orthopaedic surgeon and a physiotherapist, abstracts were reviewed and the final papers were selected for inclusion. Randomised trials or comparative cohort studies of exercise regimes were included from the clinical literature as well as systematic reviews or meta-analyses published in the last 5 years. Patello-femoral forces calculated either from in-vivo data or cadaveric simulations were included from the biomechanical literature. RESULTS: The searches revealed 3237 titles, which were reduced to 27 papers for the literature review. The biomechanical literature clearly demonstrated increasing patello-femoral forces during squats with increasing flexion, peaking at 90° of flexion and then falling in deep flexion. Less data was available on lunges but findings were comparable to studies of squats. Forces in the PFJ experienced during squats and lunges are significantly greater than with open-chain exercises beyond 60° of knee flexion. There were 13 clinical studies and 8 systematic reviews identified, which demonstrated that exercise is an effective treatment for PF pain with no significant difference between closed or open chain exercises (one study only). However only one study included squats beyond 60° or lunges in their protocols, with the majority excluding these exercises or limiting the degree of knee flexion, and no study has examined the use of squats and lunges specifically. CONCLUSION: Whilst squats and lunges are commonly prescribed, they have been used relatively little in clinical trials and have not been investigated independently. The biomechanical literature demonstrates that forces are relatively low when knee flexion is limited, but that flexion up to 90° places the PFJ under significant load. Given the vulnerable patient population in which they are used, the use of squats and lunges up to 90° should be discouraged in orthopaedic rehabilitation.