Hip muscles to target in arthiritis
Hip osteoarthritis (OA) is very common amongst an elderly population. There is a lot of research looking at the causes, the process and even potential (conservative, pharmacological and operative) treatment of osteoarthritis, but what is not as clearly understood is how the muscles of the hip are affected.
Why is this important, as clinicians we are involved in the rehabilitation of patients pre- operatively and post- operatively and therefore it is vital for us to understand which muscles are weak, how best to strengthen them and which muscles are overactive and therefore do not require strengthening
When looking at the muscles synergy around the hip we can separate superficial muscles (Gluteal max (GM), tensor fascia lata (TFL) from those in the deep system which include the gluteus medius (G.MED), gluteal minimus (G.MIN), quadratus lumborum and piriformis.
There is research suggesting that increase adduction activity, increases compressive forces through the hip and therefore may make symptoms worse. What this suggests, is that in generic home exercise programmes, exercises to strengthen adduction ought to be avoided.
The notion of considering the gluteus max as acting like 2 separate muscles carrying out two different movements has also come about of late. This due to its attachment and insertion site, the upper portion of the GM muscle (UGM) arises from the posterior iliac crest, while the lower portion of the GM muscle (LGM) arises from the inferior sacrum and upper lateral coccyx. This therefore causes the UGM, to act primarily as a hip abductor, and not play a role in hip extension unlike the LGM which is predominately a hip extensor. Both portions are believed to externally rotate the femur.
When comparing muscle wastage of patients with unilateral hip osteoarthritis, the results showed muscle wastage in the LGM of the affected hip but not the UGM. On the unaffected side the UGM experienced hypertrophy. Hypertrophy can be explained by compensation with offloading the painful side leading to increase weight bearing on the unaffected side. Commonly enough unilateral OA tends to develop into bilateral osteoarthritis.
To explain the development of bilateral OA, the theory that excessive abduction can also lead to bilateral hip OA due to the increase compressive loading has therefore been proposed. Therefore clinically once again routine hip abduction exercise targeting the superficial UGM provided for osteoarthritic patients may not be beneficial.
The emphasis is moving more towards strengthening hip extensors (LGM) and the deep abductors G.MED, G.MIN and piriformis over superficial hip abductors (UGM). The deep muscles of the hip are believed to have a part in absorbing ground reaction forces at heel strike during gait. The inabilty of these muscles to do this effectively may explain the degenerative process and pain of the hip joint.
In contrast to the above, the has also been suggestions that post total hip arthro-plasty in OA patients, GM plays an vital role in preventing surgical implants from loosening and hasten the recovery. When looking at the energy transfer and mitochondria function of a diseased OA hip, GM appeared to show greater deterioration of the intracellular energy transfer processes. The authors of this study concluded that arthroplasty undertaken before development of the grade 3 OA may improve greater post surgically as there would be fewer changes at a cellular level to the muscle.
A following article will demonstrate useful hip strengthening exercises and stretches
Grimald, A., Richardson,C.,Durbridge,G. Donnelly, W., Darnell, C., Hides, J (2009) The association between degenerative hip joint pathology and size of the gluteus maximus and tensor fascia lata muscles, Manual therapy
Eimre, M., Puhke, R., Alev, K., Seppet, E., Sikkut, A., Peet, N., Kadaja, L., Lenzner, A., Haviko, T., Seene, T., Saks, V.A., Seppet, E.K., (2006) Altered mitochondrial apparent af?nity for ADP and impaired function of mitochondrial creatine kinase in gluteus medius of patients with hip osteoarthritis, Am J Physiol Regul Integr Comp Physiol 290: R1271–R1275